I  BERKELEY 

LIBRARY 

UNIVERSITY  OF 
CALIFORNIA 

EARTH 
SCIENCES 
LIBRARY 


UNIVERSITY  OF  CALIFORNIA 

I  22  1918 


GEOGRAPHICAL 
ESSAYS 


BY 


WILLIAM  MORRIS  DAVIS 

STURGIS-HOOPER  PROFESSOR  OF  GEOLOGY,  HARVARD  UNIVERSITY 


EDITED  BY 

DOUGLAS  WILSON  JOHNSON 

ASSISTANT  PROFESSOR  OF  PHYSIOGRAPHY,  HARVARD  UNIVERSITY 


GINN  AND  COMPANY 

BOSTON   •   NEW  YORK   •  CHICAGO   •  LONDON 


COPYRIGHT,  1909 
BY  WILLIAM   MORRIS   DAVIS 


ALL    RIGHTS    RESERVED 
89.6 


QEftc  gtftenaum 


GINN  AND  COMPANY  •  PRO- 
PRIETORS •  BOSTON  •  U.S.A. 


EARTH 
SCIENCES 

EDITOR'S  NOTE  IIBRARY 


An  endeavor  has  been  made  in  this  volume  to  meet  the  grow- 
ing demand  for  an  edition  of  Professor  Davis's  most  important 
geographical  essays.  Since  it  was  not  possible  to  include  within 
the  limits  of  a  single  volume  all  essays  which  students  of  geog- 
raphy desire  to  see  reprinted,  the  editor  was  asked  to  select  a 
limited  number,  and  to  prepare  them  for  publication.  He  can 
hardly  expect  that  his  choice  will  meet  with  unanimous  approval, 
but  he  believes  it  will  appear  that  the  selections  herewith  pre- 
sented are  fairly  representative  of  the  author's  contributions  to 
the  science  of  geography. 

For  sake  of  uniformity  in  style,  method  of  treatment,  etc., 
minor  modifications  have  been  made  in  many  of  the  essays,  so 
that  they  do  not  always  conform  exactly  to  the  text  as  originally 
published.  A  large  number  of  the  illustrations  have  been  re- 
drawn, while  a  few  have  necessarily  been  omitted.  In  special 
cases  portions  of  the  text  have  been  materially  revised  to  bring 
them  into  accord  with  recent  discoveries,  or  to  eliminate  matter 
inappropriate  for  publication  under  the  present  circumstances. 
Such  alterations  as  have  been  made  have  received  the  author's 
approval.  The  original  form  of  any  essay  may  be  found  by  con- 
sulting the  citations  given  in  the  Table  of  Contents. 

The  essays  admit  of  a  natural  classification  into  two  main 
groups  :  those  concerned  chiefly  with  the  teaching  of  geography, 
included  in  Part  One,  Educational  Essays ;  and  those  dealing 
with  the  principles  of  the  science  of  geography,  more  especially 
that  branch  of  the  science  known  as  physiography,  included  in 


iv  EDITOR'S  NOTE 

Part  Two,  Physiographic  Essays.  Under  each  part  the  essays 
are  grouped  according  to  subject-matter  rather  than  in  the  order 
of  their  publication.  A  more  recent  essay  precedes  an  older 
essay  on  the  same  general  subject,  whenever  it  appears  desirable 
that  the  older  essay  should  be  read  with  a  full  knowledge  of  the 
author's  latest  opinions. 

For  the  reproduction  of  the  essays  in  the  present  form,  the 
publishers  are  indebted  to  the  several  publications  in  whose 
pages  the  essays  originally  appeared,  and  by  whose  courtesy 

they  are  reprinted  here. 

DOUGLAS  WILSON  JOHNSON 

HARVARD  UNIVERSITY 


CONTENTS 

PART  ONE  —  EDUCATIONAL  ESSAYS 

PAGE 

v    I.  AN  INDUCTIVE  STUDY  OF  THE  CONTENT  OF  GEOGRAPHY    .     .       3 
Presidential  address  at  the  second  meeting  of  the  Association  of 
American    Geographers,    December,    1905.     Bulletin  American 
Geographical  Society  (1906),  XXXVIII,  67-84. 

II.  THE  PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS  .     .     .     .     .     23 
First  Year  Book  National  Society  for  the  Scientific  Study  of  Educa- 
tion (1902),  Part  II,  7-49. 

III.  THE  PHYSICAL  GEOGRAPHY  OF  THE  LANDS  .     ......     70 

Popular  Science  Monthly  (1900),  LVII,  157-170. 

IV.  THE  TEACHING  OF  GEOGRAPHY 87 

Educational  Review  (1892),  III,  417-426;  IV,  6-15. 

V.  THE  EXTENSION  OF  PHYSICAL  GEOGRAPHY  IN  ELEMENTARY 

TEACHING 105 

An  address  delivered  before  the  Middlesex  (Massachusetts) 
Teachers  Club,  in  Boston,  October  8,  1892.  School  and  Col- 
lege (1892),  I,  599-608. 

VI.  GEOGRAPHY  IN  GRAMMAR  AND  PRIMARY  SCHOOLS     .     .     .     .115 
School  Review  (1893),  I,  327-339. 

VII.  PHYSICAL  GEOGRAPHY  IN  THE  HIGH  SCHOOL 129 

School  Review  (1900),  VIII,  388-404. 

VIII.  THE  NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY^  .....  146 
Educational  Review  (1895),  X»  22-41. 

IX.  PHYSICAL  GEOGRAPHY  AS  A  UNIVERSITY  STUDY 165 

(Last  four  pages  omitted  in  the  reprint.)  Journal  of  Geology  (1894), 
II,  66-100. 

X.  METHODS  AND  MODELS  IN  GEOGRAPHICAL  TEACHING   .     .     .   193 
A  lecture  delivered  before  the  Scientific  Association  of  Johns  Hop- 
kins University  on  February  13,  1889.    The  American  Naturalist 
(1889),  XXIII,  566-583. 

XI.  PRACTICAL  EXERCISES  IN  PHYSICAL  GEOGRAPHY 210 

Compiled  from  two  essays  on  same  subject,  one  published  in.  the 
Proceedings  Fifth  Animal  Conference  New  York  State  Science 
Teachers  Association  (1900),  the  other  published  in  National 
Geographic  Magazine  (1900),  XI,  62-78.. 

XII.   FIELD  WORK  IN  PHYSICAL  GEOGRAPHY 236 

(First  four  pages  omitted  in  reprint.)  Journal  of  Geography  (1902), 
I,  17-24,  62-69. 

v 


vi  CONTENTS 

PART  TWO  —  PHYSIOGRAPHIC  ESSAYS 

PAGE 

XIII.  THE  GEOGRAPHICAL  CYCLE 249 

Geographical  Journal  (1899),  XIV,  481—504. 

XIV.  COMPLICATIONS  OF  THE  GEOGRAPHICAL  CYCLE  .     .     ...     .  279 

Eighth  International  Geographic  Congress,  150-163. 

XV.  THE  GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE  ....  296  _ 
Journal  of  Geology  (1905),  XIII,  381-407. 

XVI.  PLAINS  OF  MARINE  AND  SUB-AERIAL  DENUDATION      .     .     .  323 
Bulletin  Geological  Society  of  America  (1896),  VII,  377—398. 

XVII.  THE  PENEPLAIN 350 

Originally  written  in  reply  to  a  paper  by  Professor  R.  S.  Tarr  on  the 
same  subject.  Reprinted  with  numerous  minor  changes.  American 
Geologist  (1899),  XXIII,  207-239. 

XVIII.  BASE-LEVEL,  GRADE,  AND  PENEPLAIN 381 

Journal  of  Geology  (1902),  X,  77-111. 

XIX.  THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA 413 

National  Geographic  Magazine  (1889),  I,  183-253. 

XX.  THE  RIVERS  OF  NORTHERN  NEW  JERSEY  WITH  NOTES  ON 

THE  CLASSIFICATION  OF  RIVERS  IN  GENERAL  .     .     .     .485 
National  Geographic  Magazine  (1890),  II,  81-110. 

XXI.  RIVER  TERRACES  IN  NEW  ENGLAND 514 

Bulletin  Museum  of  Comparative  Zoology  (1902),  XXXVIII, 
281-346. 

XXII.  THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE  .     .     .     .     .     .  587 

National  Geographic  Magazine  (1896),  VII,  189-202,  228-238. 

XXIII.  THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS 617 

Presented  in  abstract  before  Sections  C  and  E  of  the  British 
Association  at  Cape  Town,  August  17,  1905.  Scottish  Geo- 
graphical Magazine  (1906),  XXII,  76-89. 

XXIV.  GLACIAL  EROSION  IN  FRANCE,  SWITZERLAND,  AND  NORWAY  635 

Proceedings  Boston  Society  Natural  History  (1900),  XXIX,  273-322. 

XXV.  THE  OUTLINE  OF  CAPE  COD 690 

Proceedings  American  Academy  of  Arts  and  Sciences  (1896),  XXXI, 
303-332. 

XXVI.  THE  MOUNTAIN  RANGES  OF  THE  GREAT  BASIN 725 

Bulletin  Museum  of  Comparative  Zoology  (1903),  XLII,  129-177. 

INDEX  .     .  773 


GEOGRAPHICAL   ESSAYS 


PART    ONE 

EDUCATIONAL   ESSAYS 

I 

AN   INDUCTIVE   STUDY  OF   THE   CONTENT   OF 
GEOGRAPHY 

The  Need  of  Comparing  Opinions.  One  of  the  objects  to  which 
geographers  may  well  direct  their  attention  is  the  nature  of  the 
whole  subject  of  geography,  under  whose  broad  shelter  individ- 
ual studies  are  carried  on.  If  we  work  only  in  view  of  our  chosen 
field  within  the  whole  area  of  geography,  we  lose  something  of 
breadth,  although  we  may  gain  much  in  depth.  Our  work  will 
become  more  serviceable  to  others  if  it  is  presented  in  such  a 
manner  that  its  relations  to  the  whole  subject  are  made  clear. 
Not  only  so ;  we  may  often  benefit  ourselves  by  systematically 
setting  forth  the  place  of  our  individual  studies  in  geography  as 
a  whole,  for  we  may  be  thereby  led  to  discover  that  the  system- 
atic sequence  of  parts  is  interrupted  here  and  there  by  gaps, 
which  can  be  filled  by  well-directed  effort. 

But  it  is  manifest  that,  if  we  should  attempt  to  make  expo- 
sition of  our  ideas  concerning  the  relation  of  our  own  studies  to 
the  whole  subject,  we  must  have  previously  gained  a  tolerably 
definite  idea  of  the  nature  of  the  whole.  Very  likely  we  each 
have  some  such  conception.  If  so,  it  would  be  profitable  to 
institute  a  collection  and  a  comparison  of  opinions,  though  it 
can  hardly  be  doubted  that  they  would  show  much  diversity. 

Examples  of  Geographical  Statements.  As  a  contribution  to- 
wards such  a  collection  of  opinions,  I  propose  to  consider  the 
nature  or  content  of  geography  in  this  essay ;  but  instead  of 
presenting  an  abstract  definition  of  the  subject,  the  problem  will 
be  regarded  from  the  other  side.  There  will  first  be  presented 

3 


4  EDUCATIONAL  ESSAYS 

a  number  of  sample  statements  that  are  presumed  to  be  geo- 
graphical because  they  are  taken  from  geographical  works ; 
these  statements  will  then  be  analyzed  in  order  to  discover 
their  essential  nature  ;  finally,  an  attempt  will  be  made  to  dis- 
cover the  nature  of  the  whole  subject  of  geography  on  the  basis 
of  the  statements  thus  analyzed;  that  is,  to  discover  the  content 
of  geography  on  the  basis  of  an  inductive  study.  The  state- 
ments to  be  presented  are  taken  from  a  variety  of  sources  — 
text-books,  treatises,  and  journals  ;  they  are  often  condensed 
from  the  original. 

Here,  for  example,  is  a  first  set  of  items  or  statements  :  There 
are  three  native  states  in  the  Himalaya  which  are  independent 
of  British  rule.  The  rivers  of  southern  Gascony  flow  in  radiat- 
ing courses.  There  are  more  than  three  hundred  asteroids.  The 
average  man  has  about  eighty-seven  cubic  inches  of  brain." 
The  mean  depth  of  the  ocean  is  about  two  miles.  A  new  map 
of  France  on  a  scale  of  1:50,000  is  in  course  of  publication. 
Protozoa  are  the  simplest  forms  of  animals,  consisting  of  a  single 
cell.  The  magnetic  poles  do  not  coincide  with  the  poles  of  rota- 
tion. Celtic  is  spoken  in  Wales,  the  Highlands  of  Scotland,  and 
western  Ireland.  Cotton  is  produced  in  the  southern  United 
States.  The  fall  of  rivers  is  usually  greatest  in  their  upper 
courses.  The  Grand  Duchy  of  Prussia  became  a  kingdom  in  1701. 
Cryptogams  are  flowerless  plants.  The  Hindu  Kush,  the  high- 
est mountains  of  Persia,  trend  to  the  northeast.  Australia  has 
many  marsupials,  of  which  the  kangaroo  is  the  largest.  Amund- 
sen has  successfully  made  the  Northwest  Passage. 

If  all  these  statements  are  truly  of  geographical  quality,  it 
follows  that  all  similar  statements  would  be  of  geographical 
quality  also.  We  should  then  have,  in  a  complete  geography, 
accounts  of  all  states,  in  the  Himalaya  or  elsewhere,  dependent 
or  independent,  of  British  or  of  other  rule ;  descriptions  of  the 
course  of  rivers  in  all  parts  of  the  world  ;  additional  facts  about 
other  bodies  in  the  heavens  besides  the  asteroids ;  accounts  of 
man's  other  organs  than  his  brain ;  details  as  well  as  averages 
of  ocean  depths ;  descriptions  of  multicellular  as  well  as  of  uni- 
cellular animals,  and  of  flowering  as  well  as  of  flowerless  plants ; 
reports  on  old  as  well  as  on  new  maps  of  France  and  of  all  other 


CONTENT  OF  GEOGRAPHY  5 

countries,  whatever  their  scale ;  items  concerning  terrestrial 
magnetism  as  well  as  concerning  the  position  of  the  magnetic 
poles ;  reports  of  all  sorts  of  voyages  ;  accounts  of  all  changes 
of  duchies  to  kingdoms  and  of  kingdoms  to  duchies,  and  of  other 
political  changes  as  well ;  mention  of  the  animals  of  other  lands 
than  Australia,  and  of  the  products  of  other  countries  than  our 
southern  states ;  announcements  of  voyages  in  all  parts  of  the 
world  in  all  centuries. 

The  Complexity  of  Geography.  The  first  impression  about  so 
varied  a  collection  of  statements  would  be  that  the  subject  under 
which  they  are  all  properly  included  must  be  a  sort  of  omnium- 
gatherum,  without  any  well-defined  unity  of  substance.  Such, 
indeed,  geography  has  been  thought  to  be  by  some  critics.  A 
closer  examination  of  our  materials  must  be  made  in  order  to  see 
if  we  really  have  to  do  with  a  heterogeneous  collection  of  inco- 
herent facts,  without  continuity  of  thought  or  unity  of  discipline. 
It  may  be  that  some  of  the  items  above  cited  do  not  justly  be- 
long under  geography,  and  that  an  enchainment  not  apparent  at 
first  may  be  found  to  bring  the  remaining  items  and  their  proper 
fellows  into  some  systematic  association. 

On  reviewing  the  statements  given  above  it  appears  that  some 
are  concerned  with  matters  remote  from  the  earth  and  commonly 
associated  with  astronomy  ;  that  some  are  concerned  with  matters 
of  a  personal  or  technical  nature ;  that  a  third  group  of  state- 
ments contains  accounts  of  inorganic  features  of  the  earth,  and 
a  fourth  group  contains  accounts  of  organic  inhabitants  of  the 
earth.  Let  us  examine  these  several  classes  to  see  how  far  they 
may  be  justly  considered  geographical. 

Excepting  as  an  astronomical  statement  is  found  to  be  related 
to  terrestrial  matters  in  such  a  way  as  to  throw  light  on  them, 
it  should  not  be  considered  directly  or  indirectly  geographical, 
in  spite  of  the  mention  of  such  a  matter  in  a  geographical  text- 
book ;  for  by  common  consent  geography  has  to  do  primarily 
with  the  earth.  Hence  the  mere  statement  of  the  number  of 
asteroids  should  be  excluded  from  our  consideration.  It  may, 
however,  be  advisable  to  retain  in  elementary  text-books  certain 
statements  concerning  planets  in  so  far  as  they  serve  to  em- 
phasize the  globular  form  of  the  earth  by  showing  that  there  are 


6  EDUCATIONAL  ESSAYS 

other  bodies  like  it,  and  such  mention  of  the  sun  and  moon  as  is 
needed  for  the  understanding  of  insolation  in  relation  to  climate 
and  of  gravitation  in  relation  to  tides ;  also  such  account  of  the 
stars  as  shall  serve  in  the  proof  of  the  rotation  of  the  earth  and 
in  the  determination  of  the  attitude  of  its  axis.  Nevertheless, 
all  these  items  seem  to  be  only  indirectly  associated  with  our 
subject ;  they  do  not  aid  us  to  discover  the  real  nature  of 
geography. 

Technical  and  personal  items  may  naturally  be  associated  with 
geography  if  the  things  and  events  with  which  they  are  con- 
cerned are  of  a  geographical  quality,  as  maps  and  explorations 
certainly  are.  The  announcement  of  the  publication  of  a  new 
map  or  of  the  completion  of  a  remarkable  voyage  is  therefore  a 
piece  of  appropriate  geographical  news.  Accounts  of  old  maps, 
of  old  voyages,  and  of  old  ideas  are  very  illuminating  in  showing 
how  the  geography  of  to-day  has  been  developed,  but  they  be- 
long more  with  history  than  with  geography  when  presented  in 
order  of  time. 

Non-Geographical  Statements.  Many  of  the  statements  under 
the  two  remaining  classes  —  which  concern  inorganic  and  organic 
matters  on  the  earth  —  are  properly  geographical  if  we  judge  by 
the  repeated  occurrence  of  such  statements  in  many  geographical 
works.  Yet  we  cannot  believe  that  all  statements  about  inorganic 
and  organic  matters  on  the  earth  belong  under  geography.  It  is 
easy  to  instance  a  number  of  such  statements  from  geographical 
sources  which  can  hardly  be  regarded  as  having  any  clear  associ- 
ation with  geography.  Consider,  for  example,  the  following  set 
of  items,  all  taken  from  geographical  text-books  : 

The  gastrula  stage  occurs  just  before  maturity  in  the  sponge.  All  sub- 
stances transmit  electrical  energy.  Crystallization  is  explained  by  supposing 
that  the  cohesive  force  of  molecules  is  not  exerted  equally  on  all  sides. 
After  1 8 10,  several  independent  republics  were  formed  in  South  America. 
The  Rosaceae  have  regular  flowers. 

However  interesting  and  useful  these  items  of  information  may 
be,  they  can  hardly  be  regarded  as  geographical,  even  under  the 
very  broadest  interpretation  of  our  subject.  They  have  probably 
been  added  to  the  text-books  from  which  they  are  quoted  in  the 
belief  that  they  are  worth  knowing,  and  that  the  pupils  in  our 


CONTENT  OF  GEOGRAPHY  7 

schools  will  have  little  chance  of  learning  them  if  they  are  not 
brought  in  under  the  popular  subject  of  geography.  I  question 
the  advisability  of  such  a  method  of  promoting  popular  educa- 
tion ;  but  that  is  another  story.  Our  problem  is  to  distinguish 
these  and  many  similar  statements  from  a  large  variety  of  other 
statements  concerning  the  inorganic  and  organic  terrestrial  mat- 
ters, so  as  to  know  which  are  properly  of  geographical  quality 
and  which  are  not. 

Statements  involving  Relations.  The  best  solution  that  I 
have  been  able  to  find  for  this  problem  comes  from  a  considera- 
tion of  such  statements  as  are  included  in  the  following  third 
set  of  extracts,  which,  like  the  other  two,  have  been  taken  from 
geographical  sources  : 

The  people  of  the  Dalmatian  coast  are  largely  engaged  as  fishermen  on 
the  Adriatic  ;  Jiere  the  Austrian  navy  obtains  its  best  seamen.  A  number 
of  gulfs  and  mountain  ranges  naturally  divide  the  people  of  Europe  into 
groups  or  nations.  Some  parts  of  Bengal  are  so  favored  with  rivers  that 
almost  every  cottage  has  a  navigable  stream  at  its  door,  and  the  Bengalese 
farmer  keeps  his  boat,  just  as  the  English  farmer  keeps  his  gig.  Northern 
Uganda  is  drier,  rain  often  fails,  grass  is  short,  and  dry-country  animals, 
such  as  zebras  and  ostriches,  abound.  The  level  land  near  lake  Ti^icaca  is 
of  small  extent,  and  is  occupied  by  alkaline  marshes  subject  to  overflow  ; 
for  this  reason  the  Indians  cultivate  the  slopes  in  preference,  converting 
them  into  narrow  terraced  garden  beds.  The  periodic  or  monsoon  winds 
that  blow  alternately  now  in  one  direction  and  now  in  the  opposite  along 
certain  coasts,  as  between  India  and  East  Africa,  have  long  been  favorable 
to  navigation  and  trade.  In  northwest  France  the  farm-houses  on  the  chalk 
uplands  are  gathered  into  compact  villages  around  one  or  more  deep  wells, 
because  the  ground  water  there  is  deep  below  the  surface  and  difficult  to 
obtain  ;  but  in  the  valleys  the  houses  are  scattered,  because  each  family 
can  easily  procure  its  own  water  supply  with  little  trouble. 

Geography  a  Study  of  Relations.  These  statements  differ  from 
some  of  those  of  the  two  earlier  groups  of  citations  in  that  they 
each  contain  at  least  two  kinds  of  elements,  one  of  which  stands 
in  a  more  or  less  distinctly  causal  relation  to  the  other.  The 
statements  vary  in  that  some  of  the  relations  suggested  are  rela- 
tively simple,  while  others  are  more  complex,  and  in  that  some 
statements  are  rather  empirical,  while  others  are  more  fully  ex- 
planatory ;  but  they  are  all  alike  in  that  they  involve  a  relation 
of  cause  and  effect,  usually  between  some  element  of  inorganic 


8  EDUCATIONAL  ESSAYS 

control  and  some  element  of  organic  response.  As  such,  these 
statements  are  examples  of  the  most  generally  treated  material 
that  I  can  find  ;  and  hence  I  am  disposed  to  say  that  any  state- 
ment is  of  geographical  quality  if  it  contains  a  reasonable  rela- 
tion between  some  inorganic  element  of  the  earth  on  which  we 
live,  acting  as  a  control,  and  some  element  of  the  existence  or 
growth  or  behavior  or  distribution  of  the  earth's  organic  inhab- 
itants, serving  as  a  response ;  more  briefly,  some  relation  between 
an  element  of  inorganic  control  and  one  of  organic  response.  The 
geographical  quality  of  such  a  relation  is  all  the  more  marked 
if  the  statement  is  presented  in  an  explanatory  form.  There  is, 
indeed,  in  this  idea  of  a  causal  or  explanatory  relationship  the 
most  definite,  if  not  the  only,  unifying  principle  that  I  can  find 
in  geography.  All  the  more  reason,  then,  that  the  principle 
should  be  recognized  and  acted  upon  by  those  who  have  the 
fuller  development  of  geographical  science  at  heart. 

Geography  as  the  Study  of  Location  or  of  Distribution.  There 
still  exists  in  some  quarters  a  tendency  to  limit  geography  by 
definition  to  the  study  of  location,  leaving  the  study  of  all  the 
things  that  are  located  to  other  subjects.  There  is  so  little  sup- 
port for  this  narrow  view  of  the  subject  to  be  found  in  modern 
geographical  books  that  it  need  not  be  further  considered.  An- 
other and  more  widely  accepted  definition  treats  geography  as 
the  science  of  distribution.  This  is  particularly  a  British  view 
of  the  subject,  and  at  least  one  British  geographer  urges  that 
the  distributed  things  should  not  be  regarded  as  belonging  to 
geography  at  all ;  but  his  writings  are  broader  than  his  defini- 
tion. While  location  and  distribution  must  always  be  important 
elements  of  geography,  all  geographical  books  give  much  atten- 
tion to  the  nature  of  the  things  that  are  distributed,  and  all  recent 
books  give  much  weight  to  the  relations  in  which  the  distributed 
things  occur ;  hence  relationship  seems  to  me  the  primary  prin- 
ciple of  the  two,  and  distribution  takes  a  secondary  rank.  The 
thing  must  be  known  before  its  distribution  can  be  serviceably 
studied.  The  division  of  the  peoples  of  Europe  into  groups  or 
nations  in  consequence  of  the  division  of  Europe  by  gulfs  and 
mountain  ranges  is  a  geographical  relation,  in  which  the  unlikeness 
of  the  things  distributed  takes  precedence  of  their  distribution. 


CONTENT  OF  GEOGRAPHY  9 

Indeed,  if  geography  were  only  the  science  of  distribution,  — 
that  is,  the  regional  aspect  of  other  subjects,  —  it  would  be  hardly 
worth  while  to  maintain  the  study  of  geography  apart  from  that 
of  the  subject  whose  regional  aspect  it  considers.  Moreover,  if 
geography  is  defined  simply  as  the  science  of  distribution,  then 
the  distribution  of  anything  is  a  fit  subject  for  geographical 
study.  Under  such  a  definition  the  distribution  of  hypersthene 
andesite,  or  of  books  of  poetry,  would  be  part  of  our  responsi- 
bility ;  but  there  is  nowhere  any  indication  that  geographers  feel 
responsible  for  the  distribution  of  such  things.  Again,  if  distri- 
bution is  given  first  rank,  the  regional  or  spacial  occurrence  of 
all  sorts  of  things  is  thereby  given  so  great  an  importance  that 
an  insufficient  place  is  left  for  systematic  considerations ;  yet 
most  books  first  present  things  of  a  kind  together — that  is,  they 
present  the  subject  systematically  —  before  they  take  up  the 
distributional  or  regional  treatment  of  different  kinds  of  things. 
Moreover,  distributional  treatment  is  too  apt  to  take  up  one  kind 
of  thing  at  a  time,  and  follow  it  wherever  it  is  found,  thus  failing 
to  give  account  of  the  natural  occurrence  of  many  kinds  of  things 
in  their  actual  association  which  regional  geography  demands. 

As  a  matter  of  fact,  nearly  every  example  that  is  presented 
in  this  essay  as  an  example  of  a  geographical  relation  might,  if 
desired,  be  presented  as  an  example  of  distribution,  and  nearly 
all  statements  of  distribution  may  be  turned  around  so  that  they 
shall  enter  into  or  constitute  relations ;  hence  the  total  content 
of  geography  would  be  much  the  same  under  either  principle. 
The  relations  that  could  not  be  presented  under  the  head  of 
distribution  are  those  which  are  the  same  everywhere ;  but  it 
seems  to  me  rather  arbitrary  to  include  relations  that  vary  from 
place  to  place,  and  to  exclude  relations  that  are  world-wide  in 
their  uniform  occurrence.  For  example,  the  composition  of  the 
atmosphere  or  of  the  ocean,  always  accepted  as  an  appropriate 
matter  for  mention  in  elementary  texts,  deserves  no  place  in 
geography,  treated  as  the  science  of  distribution,  until  the  minute 
variations  of  composition  from  place  to  place  are  considered. 

In  any  case,  location  and  distribution  are  fundamental  elements 
of  geography,  and  maps  of  the  lands  and  charts  of  the  oceans 
are  essential  in  its  every  chapter.  In  view  of  the  importance  of 


10  EDUCATIONAL  ESSAYS 

these  elements,  some  are  disposed  to  attach  an  undue  value  to 
surveying  as  a  part  of  geography.  But  surveying  properly  be- 
longs in  geography  about  where  writing  belongs  in  literature, 
and  if  it  is  given  higher  rank  the  student  may,  by  misfortune, 
turn  his  chief  attention  to  the  art  of  mapping  instead  of  to  a 
study  of  the  things  that  are  mapped. 

Regional  Geography.  It  has  been  well  maintained  by  certain 
German  geographers  that  geography  is  concerned  with  the  ''ma- 
terial filling  of  space";  that  is,  geography  has  to  deal  with 
regions  or  districts,  as  occupied  by  all  the  kinds  of  things  that 
there  occur  together.  This,  however,  is  only  the  regional  aspect 
of  geography,  and  before  it  can  be  treated,  the  geographer  must 
have  a  good  acquaintance  with  the  different  kinds  of  things  that 
occur  in  various  regions,  that  is,  with  systematic  geography.  It 
is  with  this  second  aspect  of  the  subject  that  we  are  here  chiefly 
concerned. 

Physiography  and  Ontography.  If  the  principle  of  explanatory 
relationship  be  adopted  as  a  general  guide  to  the  content  of 
geography,  it  follows  that  neither  the  inorganic  nor  the  organic 
elements  which  enter  into  geographical  relations  are  by  them- 
selves of  a  completely  geographical  quality  ;  they  gain  that  qual- 
ity only  when  two  or  more  of  them  are  coupled  in  a  relation  of 
cause  and  effect,  at  least  one  element  in  the  chain  of  causation 
being  inorganic  and  one  organic.  When  they  are  considered 
separately,  but  as  if  in  preparation  for  an  understanding  of  the 
causal  relations  in  which  they  will  later  be  presented  in  the  study 
of  geography  proper,  they  may  be  considered  as  sub-geographical; 
and  then  the  inorganic  elements  may  be  called  physico-geo- 
graphic,  or  physiographic,  and  the  organic  elements  may  be 
called  ontographic.  Common  usage  recognizes  the  first  of  these 
divisions,  but  not  the  second,  as  we  shall  see  later.  It  is  well  to 
emphasize  the  clause  "  as  if  in  preparation  for  an  understanding 
of  the  causal  relations  in  which  they  will  later  be  presented  in 
the  study  of  geography  proper"  ;  for  many  items  which,  under 
this  proviso,  are  of  physiographic  or  of  ontographic  quality,  may 
under  another  proviso  belong  in  other  departments  of  knowledge. 

Physiographic  Matters.  This  may  be  made  plainer  by  citing 
particular  cases  in  which  a  number  of  different  topics,  familiar 


CONTENT  OF  GEOGRAPHY  II 

from  their  occurrence  in  books  on  geography,  will  be  seen  to 
fall  under  other  subjects  when  they  enter  into  non-geographical 
relations.  For  example,  the  size  and  rotation  of  the  earth,  and  the 
general  movements  of  the  tides,  are  undoubtedly  physiographic 
elements,  yet  both  may  be  treated  appropriately  under  astronomy 
when  they  are  considered  in  their  relations  to  other  planets. 
Sea  water,  when  regarded  as  a  liquid  compound  which  holds 
various  salts  in  solution,  may  be  studied  properly  by  the  chemist 
with  regard  to  its  composition;  nevertheless,  sea  water  as  the 
medium  in  which  organic  forms  live  is  an  indispensable  subject 
for  physiographic  inquiry.  The  horizontal  strata  of  plateaus  are 
a  fit  topic  for  geological  investigation,  as  regards  their  origin 
and  history,  but  they  are  no  less  a  subject  for  physiographic  in- 
vestigation as  affecting  present  form.  It  therefore  seems  impos- 
sible to  determine,  merely  by  a  consideration  of  the  thing  studied, 
whether  it  belongs  to  physiography  or  not. 

^  given  object  may  belong  under  several  different  sciences, 
and  may  be  treated  in  text-books  on  different  subjects ;  it  is  the 
relation  into  which  the  object  enters  that  determines  its  place. 

There  are,  however,  certain  inorganic  topics,  commonly  found 
in  geographical  books,  which  seldom,  if  ever,  enter  into  relations 
with  organic  topics,  and  which  would,  therefore,  under  the  strict 
application  of  the  principle  of  relationships,  be  ruled  out  of  physi- 
ography, and  thus  out  of  geography  also.  Such  are  cirrus  clouds 
and  halos,  the  crevasses  and  blue  veins  of  glaciers,  and  the  polar 
flattening  of  the  earth.  Nevertheless,  most  or  all  of  these  topics 
will  probably  hold  their  places  in  books  on  physiography,  because 
they  serve  to  complete  the  picture  of  the  whole  earth  as  the 
home  of  life.  In  any  case,  little  is  gained  by  a  very  strict  or 
over-logical  application  of  a  useful  principle  of  classification  in  a 
problem  such  as  we  are  considering. 

Ontographic  Matters.  The  determination  of  the  science  under 
which  a  thing  belongs  by  means  of  the  relations  into  which  the 
thing  enters  is  an  even  more  important  guide  in  ontography  than 
in  physiography.  For  example,  one  may  read  in  a  certain  text- 
book of  geography  that  all  forms  of  life  consume  food.  In  so 
far  as  the  assimilation  of  food,  and  the  organs  by  which  it  is 
accomplished,  are  concerned,  the  consumption  of  food  belongs 


12  EDUCATIONAL  ESSAYS 

under  physiology  ;  but  the  consumption  of  food  is  an  ontographic 
matter  in  so  far  as  it  brings  an  organism  into  contact  with  the 
rest  of  the  world  and  thus  causes  it  to  enter  into  geographical 
relations.  Commercial  geography  is  largely  concerned  with  re- 
lations that  grow  out  of  this  element  of  ontography.  Water  is 
essential  in  organic  processes  of  many  kinds.  This  is,  again,  a 
physiological  matter  if  it  is  examined  with  reference  to  the 
processes  of  circulation,  but  it  is  ontographic  when  it  is  found 
to  lead  to  a  relation  with  the  sources  of  water  supply  :  villages 
gathered  around  deep  wells  on  the  chalk  uplands  of  north- 
western France  are  examples  of  the  geographical  relation  thus 
brought  about. 

Plants  and  animals  tend  to  diffuse  themselves,  or  to  be  dif- 
fused, over  the  earth.  This  is  a  fundamental  fact,  usually  asso- 
ciated with  the  study  of  biology  ;  but  the  limits  of  diffusion,  and 
in  many  cases  the  means  of  diffusion,  are  determined  by  physio- 
graphic controls ;  hence  the  tendency  to  diffusion  is  an  onto- 
graphic matter. 

The  need  experienced  by  all  forms  of  life  to  secure  food, 
already  instanced,  leads  to  many  other  relations  than  those  of 
commercial  geography.  The  need  of  food  is  satisfied  without 
going  in  search  of  it  if  the  food  is  contained  in  a  moving 
medium  that  surrounds  the  organism ;  hence  those  organisms 
that  live  chiefly  upon  food  contained  in  one  or  the  other  of  the 
two  great  mobile  envelopes  of  the  earth  —  the  atmosphere  or 
the  hydrosphere  —  are  often  rooted  or  fixed  :  the  air  or  water 
currents  carry  the  needed  food  to  the  waiting  plant  or  animal, 
and  this  is  surely  too  important  a  geographical  relation  to  be 
omitted  from  a  broad  consideration  of  our  subject.  Other 
organisms  take  advantage  of  the  currents  of  air  or  water  to  be 
passively  carried  about  by  them,  taking  their  food  when  they 
happen  to  come  upon  it.  If  they  are  land  dwellers,  they  are  so 
small  that  they  can  easily  be  wafted  about  by  the  winds  ;  if  they 
are  dwellers  in  water,  they  may  gain  greater  size  by  assuming 
about  the  same  specific  gravity  as  that  denser  medium,  so  as  to 
float  easily  in  its  perpetual  currents.  Still  a  third  class  of  organ- 
isms move  of  their  own  volition,  and  in  connection  with  these 
there  are  all  manner  of  geographical  relations.  Some  of  them 


CONTENT  OF   GEOGRAPHY  13 

involve  the  development  of  wings,  whereby  motion  can  be 
effected  in  the  comparatively  unsustaining  air,  as  in  the  case 
of  many  insects  and  birds,  of  a  few  mammals,  and  formerly  of 
some  reptiles ;  some  involve  the  development  of  fins  to  produce 
motion  in  the  sustaining  water.  These  examples  are  as  good 
illustrations  of  organic  responses  to  inorganic  controls  as  are  the 
canoes  and  the  steamships  of  uncivilized  and  of  civilized  man. 

It  follows  from  the  preceding  paragraph  that  the  more  closely 
our  standard  geographical  material  is  examined,  the  more  clearly 
it  appears  that  its  ontographic  as  well  as  its  physiographic  ele- 
ments may  fall  into  other  sciences  when  they  are  treated  in  other 
relations,  and  that  they  become  most  distinctly  geographical  when 
they  enter  into  the  causal  relations  of  the  kind  set  forth  above. 
The  rise  and  fall  of  the  tides  is  a  physiographic  matter  when  it 
is  seen  to  determine  the  distribution  of  certain  forms  of  life,  such 
as  barnacles,  or  to  influence  the  availability  of  harbors  for  the 
entrance  of  shipping ;  the  occurrence  of  coal  is  a  physiographic 
matter  when  it  is  found  to  influence  the  industry  of  a  district 
and  the  commerce  between  nations  ;  the  small  size  of  spores, 
pollen,  and  germs  is  an  ontographic  matter  when  it  is  seen  to 
be  related  to  their  transportation  by  the  thin  air ;  the  sensitive- 
ness of  organisms  to  temperature  changes  is  an  ontographic 
matter  when  it  is  shown  to  affect  the  distribution  of  plants  and 
animals  over  the  earth.  Yet  all  these  matters  may  be  treated 
with  entire  justice  under  other  sciences  than  geography.  It  is, 
therefore,  to  my  reading,  of  capital  importance,  in  determining 
whether  a  statement  is  of  geographical  or  of  sub-geographical 
nature,  to  know  how  far  it  constitutes  or  enters  into  causal  rela- 
tions of  the  kinds  that  have  here  been  considered. 

Is  Ontography  a  Part  of  Geography  ?  It  is  perfectly  true  that 
many  of  the  illustrations  just  given  are  not  commonly  regarded 
as  belonging  under  geography,  but  it  seems  to  me  that  their 
exclusion  is  illogical  and  arbitrary.  They  are  practically  all  to 
be  found  in  certain  standard  geographical  works,  and  many  more 
might  be  taken  from  such  books  as  Ratzel's  "  Anthropogeogra- 
phie  "  and  Beddard's  "  Zoogeography."  The  general  principle 
by  which  one  should  be  guided  in  determining  the  relevancy  of 
such  matters  is  as  follows  :  If  a  certain  relation  between  an 


14  EDUCATIONAL  ESSAYS 

inorganic  control  and  a  responding  organism  is  a  geographical 
relation,  then  all  similar  relations  are  also  geographical.  For  ex- 
ample, a  well-known  text-book  makes  the  statement  that  water 
plants  are  supported  by  the  relatively  dense  medium  in  which  they 
grow,  and  hence  do  not  need  strong,  woody  stalks  such  as  many 
land  plants  have.  This  is  an  excellent  example  of  a  geographical 
fact :  it  involves  a  relation  between  an  organic  growth  and  an 
inorganic  medium.  But  the  flight  of  birds,  the  small  size  of 
germs,  the  essential  agreement  between  the  specific  gravity  of 
fish  and  of  water,  the  universal  habit  of  breathing  oxygen,  —  all 
involve  similar  relations.  The  first  example  seems  to  me  unde- 
niably geographical ;  the  others  are  no  less  so.  To  exclude  the 
latter  from  geography  while  including  the  former  would  be  to 
set  very  arbitrary  limits  to  our  subject. 

It  may,  perhaps,  be  objected  that  flight  and  breathing  are 
processes  of  too  ancient  origin  to  be  considered  as  geographical, 
but  inasmuch  as  they  have  been  maintained  to  the  present  time 
by  inheritance  through  persistent  conditions  of  environment,  they 
have  the  same  right  to  a  place  under  geography  as  is  enjoyed 
by  such  examples  as  the  prevalence  of  the  fishing  industry  on 
the  Dalmatian  coast,  or  the  custom  of  the  French  farmers  on 
the  chalk  uplands  of  living  in  compact  villages  ;  for  these  habits, 
also,  are  not  independently  originated  by  each  man  who  follows 
them,  but  are  continued  by  inheritance  through  persistent  con- 
ditions of  environment. 

There  are  certain  matters  frequently  encountered  in  text-books 
of  physical  geography  which  belong  better,  it  seems  to  me,  under 
the  head  of  ontographic  relations.  Such  are  the  distribution 
of  plants  and  animals,  and  the  races  of  man.  The  association 
of  such  topics  with  physical  geography  is  probably  the  result 
of  conceiving  all  the  rest  of  the  subject  as  contained  under 
political  geography.  The  contrast  of  physical  with  political 
conditions  may  serve  well  enough  in  elementary  books,  where 
the  distribution  and  behavior  of  man  are  the  chief  subjects  in 
political  geography,  and  where  plants  and  animals  are  therefore 
thrown  in  with  physical  geography  ;  but  in  the  more  advanced 
and  general  treatment  of  the  subject  such  an  arrangement  is 
not  satisfactory.  It  does,  however,  seem  legitimate  to  introduce 


CONTENT  OF  GEOGRAPHY  15 

as  often  as  desired  ontographic  responses  in  a  physiographic 
text,  in  order  to  show  at  once  the  kind  of  response  that  certain 
controls  call  forth,  and  thus  to  impress  the  fact  that  the  physio- 
graphic items  are  really  related  to  ontographic  items  ;  a  similar 
introduction  of  physiographic  items  is  appropriate  in  chapters 
on  ontography.  This  practice  is  followed  by  certain  writers.  ' 

There  are  three  definite  positions  and  many  indefinite  positions 
that  might  be  taken  with  respect  to  the  attention  that  should  be 
given  by  geographers  to  organic  considerations.  The  narrowest 
position  limits  geography  almost  entirely  to  the  inorganic  fea- 
tures of  the  earth,  —  that  is,  to  physical  geography,  or  physiog- 
raphy. This  is  the  view  of  geography  held  by  some  historians, 
who  take  unto  themselves  practically  all  the  human  element  that 
is  so  commonly  encountered  in  political  geography.  An  inter- 
mediate position  would  include  physiography  and  the  more  mani- 
fest relations  into  which  it  enters  with  various  forms  of  life,  and 
particularly  with  man,  but  would  not  accept  responsibility  as  to 
the  less  manifest  responses  of  various  living  things.  This  seems 
to  be  the  position  taken  by  many  geographers,  more  or  less  con- 
sciously. The  third  position  would  treat  ontography  as  thor- 
oughly as  physiography,  and  would  search  for  all  the  geographical 
relations  of  physiographic  controls  and  ontographic  responses. 
This  is  certainly  the  broadest  of  the  three  positions,  being,  as 
many  would  feel,  too  broad,  and  involving  too  much  overlapping 
upon  other  subjects.  For  my  own  part,  there  seems  to  be  so 
manifest  a  necessity  of  gaining  a  responsible  knowledge  of  ontog- 
raphy, at  least  of  elementary  ontography,  before  geography 
proper  can  be  successfully  treated,  that  ontography  should  come 
to  be  regarded  as  a  part  of  it.  The  analytical  and  inductive 
methods  of  this  paper,  therefore,  lead  me  to  adopt  the  third 
position ;  and  I  believe  that  this  position  is  essentially  consist- 
ent with  the  opinion  of  writers  who,  like  Ratzel  and  Reclus, 
have  cultivated  the  most  advanced  or  matured  stage  of  geo- 
graphical science. 

The  Importance  of  Explanatory  Relations.  Although  various 
facts  which  may  make  parts  of  relations  between  inorganic  con- 
trols and  organic  responses,  or  which  are  met  with  in  prepara- 
tion for  an  understanding  of  such  relations,  thereby  gain  a  most 


1 6  EDUCATIONAL  ESSAYS 

•characteristic  geographical  flavor,  a  very  brief  review  of  geo- 
graphical books  will  suffice  to  show  that  many  statements  there 
included  do  not  explicitly  possess  this  flavor.  In  the  first  place, 
in  the  older  books  the  idea  of  relationship  had  no  distinct  recog- 
nition. That  was  the  time  of  memorized  names  of  capes,  of 
empty  boundaries,  of  unexplained  lists  of  products.  Almost 
anything  about  the  earth  or  its  inhabitants  was  then  accepted  if 
it  reached  a  satisfactory  degree  of  what  is  called  "  importance." 
In  the  newer  books  the  principle  of  explanatory  relationship  is 
very  generally  acted  upon ;  there  are,  nevertheless,  many  rela- 
tions stated  so  empirically  that  the  pupil  may  fail  to  gain  from 
them  a  full  appreciation  of  the  best  essence  of  geography.  Con- 
sider, for  example,  the  following  statement  from  a  good  text- 
book :  "  Some  form  of  Celtic  is  spoken  in  Wales,  the  Highlands 
of  Scotland,  and  western  Ireland."  This  is  nothing  more  than 
an  empirical  statement  of  a  fact  of  distribution.  Many  a  student 
might  memorize  such  an  item  without  gaining  any  clear  insight 
into  its  geographical  meaning.  The  real  point  is  that  the  early 
inhabitants  of  Great  Britain,  being  attacked  by  invaders  from 
the  continent  on  the  east,  survived  only  where  pursuit  was  diffi- 
cult, as  in  the  rough  ground  of  Wales,  in  the  rough  and  distant 
ground  of  the  Highlands,  or  in  the  distant  and  isolated  ground 
of  Ireland  ;  and  hence  only  in  those  localities  is  the  early  lan- 
guage still  preserved.  The  fact  that  Celtic,  as  Celtic,  is  spoken 
in  certain  parts  of  Great  Britain  belongs  to  philology  as  well  as 
to  any  other  subject ;  the  fact  that  Celtic  is  the  language  that 
was  once  spoken  generally  through  Great  Britain  might  come 
under  history  as  well  as  under  any  other  subject ;  but  the  fact 
that  Celtic  is  still  spoken  in  rough,  distant,  or  isolated  parts  of 
Great  Britain,  because  of  their  roughness,  distance,  or  isolation, 
is  a  local  example  of  an  important  class  of  relations  between 
controls  and  responses,  and  as  such  it  belongs  distinctly  under 
rational  geography. 

The  Expansion  of  Geography.  Geography  has  still  much  prog- 
ress to  make.  There  is  not  only  much  to  be  done  in  the  way  of 
exploration  of  little-known  lands  and  seas,  but  many  of  the  more 
civilized  countries  still  merit  closer  study  than  they  have  yet  re- 
ceived if  we  may  judge  by  the  notable  incompleteness;  of  the 


CONTENT  OF  GEOGRAPHY  17 

best  handbooks  and  treatises.  One  method  of  carrying  the  sub- 
ject forward  consists  in  outdoor  observation,  and  this  method 
canno.t  be  too  highly  recommended  to  those  who  wish  to  con- 
tribute to  the  fuller  development  of  our  subject.  When  we  real- 
ize that  we  have  no  modern  and  maturely  developed  account  of 
the  geography  of  such  a  state  as  Virginia,  or  Ohio,  or  Colorado, 
or  California,  it  becomes  evident  that  abundant  opportunity  for 
exploration  lies  near  home.  But  there  is  a  second  method  by 
which  geography  may  be  promoted  ;  that  is,  by  thinking  about 
what  we  see,  and  thus  expanding  every  example  of  a  geographical 
relation  that  we  find  to  its  farthest  legitimate  extension.  Take, 
for  example,  the  common  case  of  a  road  which  runs  through  a 
notch  in  a  high  ridge ;  such  a  detail  of  location  is  a  response  of 
the  ontographic  element,  movement,  to  the  physiographic  control, 
gravity ;  hence  all  such  responses  to  gravity  should  be  searched 
out  so  that  they  may  be  systematically  treated  as  to  kind,  and 
regionally  treated  as  to  distribution.  Such  matters  are  surely  as 
properly  of  a  geographical  quality  as  are  various  responses  to 
sunshine  which  are  always  found  among  the  standard  matters  of 
our  books.  How  many  more  responses  to  the  universal  and  per- 
sistent force  of  gravity  there  may  be,  we  do  not  yet  know.  Again, 
take  such  an  example  as  that  afforded  by  the  habit  of  working 
by  day  and  summer  and  resting  by  night  and  winter.  These  are 
responses  to  the  controls  of  light  and  heat  in  contrast  to  dark- 
ness and  cold,  which  result  from  the  illumination  and  warmth  of 
the  rotating  and  revolving  earth  by  an  external  sun.  This  sug- 
gests that  all  other  responses  to  light  and  to  darkness  should  be 
sought  out  and  studied  :  for  it  leaves  the  limitations  of  our  sub- 
ject very  vague  if  we  make  a  beginning  with  such  relations  and 
do  not  carry  them  to  an  end  ;  it  makes  the  limitations  very 
arbitrary  if  we  make  a  beginning  of  such  relations  and  stop  with 
the  first  or  the  second  or  the  third  example,  instead  of  pressing 
on  to  the  very  last. 

It  is  an  application  of  this  same  principle  that  makes  it  im- 
possible to  limit  the  organic  side  of  geography  to  man ;  for  the 
habits  which  man  has  developed  in  his  search  for  food,  clothing, 
shelter,  and  so  on,  are  in  very  many  ways  closely  analogous  to 
those  developed  by  animals  in  a  similar  search.  In  the  same  way 


1 8  EDUCATIONAL  ESSAYS 

the  sensitiveness  of  man  and  animals  to  climatic  conditions  by 
which  limits  of  distribution  are  so  largely  determined  is  paral- 
leled by  the  sensitiveness  of  plants  to  similar  conditions.  Life  is 
a  unit ;  if  one  form  of  life  comes  under  the  study  of  geography 
because  it  responds  to  physiographic  controls,  then  all  forms  of 
life  come  under  geography. 

The  expansion  of  geography  through  time  is  likewise  inevi- 
table unless  it  is  most  arbitrarily  limited  to  the  "  present  day." 
Precisely  the  same  principles  have  been  embodied  in  the  rela- 
tions between  physiographic  and  ontographic  elements  in  the 
past  as  are  embodied  in  them  now.  It  is  therefore  most  illogical 
to  think  of  geography  as  a  science  that  deals  only  with  to-day. 
There  has  always  been  a  geography,  all  through  the  geological 
ages  ;  geology  is  the  integration  of  all  its  momentary  or  geo- 
graphical differentials.  We  may  never  know  very  much  about 
the  successive  geographies  of  the  past,  but  all  the  fragments 
that  have  thus  far  been  learned  assure  us  that  it  was  of  essen- 
tially the  same  order  as  the  geography  of  the  present.  The 
recognition  of  this  principle  is  of  the  greatest  importance  to 
geography,  and  to  geology  as  well. 

The  Subdivisions  of  Geography.  It  is  but  natural  that  the 
different  phases  of  human  geography  should  have  been  more 
fully  developed  than  the  other  branches  of  our  science.  Political 
geography,  frequently  overrunning  civics,  economics,  and  history, 
has  long  been  familiar  as  an  elementary  subject ;  but  with  us  it 
has  seldom  been  carried  into  the  higher  reaches  of  education. 
Commercial  geography  is  rapidly  gaining  an  important  place  in 
our  schools,  and  is  meeting  the  danger  of  becoming  almost  as 
empirical  as  the  old-time  lists  of  products  of  the  several  states. 
Biogeography  has  several  parts.  Anthropogeography,  as  ex- 
panded by  Ratzel,  seems  destined  to  become  an  important  sub- 
ject in  the  universities,  because  of  the  greater  insight  that  one 
gains  through  it  into  history.  Zoogeography  and  phytogeography 
are  in  my  opinion,  as  a  rule,  too  strictly  limited  to  facts  of  distri- 
bution alone ;  these  divisions  of  the  subject  should  be  expanded 
so  as  to  include  for  animals  and  plants  a  consideration  of  what 
would  correspond  to  the  political  and  commercial  geography  of 
man.  Paleogeography  is  occasionally  treated,  but  it  must  always 


CONTENT  OF  GEOGRAPHY  19 

be  a  fragmentary  subject,  because  it  is  based  on  fragmentary 
records  ;  it  will,  however,  be  better  treated  by  geologists  in  pro- 
portion as  they  have  had  geographical  training. 

The  growth  of  explanatory  treatment,  which  makes  so  char- 
acteristic a  difference  between  the  content  of  geography  in  books 
of  a  hundred  years  ago  and  of  to-day,  is  chiefly  due  to  the  differ- 
ent amounts  of  general  knowledge  in  stock  then  and  now,  and 
consequently  to  the  different  philosophies  then  and  now  prevail- 
ing. The  subject  has  thus  gained  greatly  in  strength,  in  disci- 
plinary value,  and  in  living  interest.  At  the  same  time  geography 
has  come  to  cultivate  more  and  more  —  some  would  say,  to  tres- 
pass more  and  more  upon  —  the  fields  that  are  also  cultivated  by 
other  subjects.  If  the  trade  winds  are  not  simply  described  as 
to  region  of  occurrence,  direction  of  blowing,  weather  conditions 
therein  prevailing,  and  so  on,  but  are  also  explained  as  parts  of 
an  extensive  convectional  circulation  between  equator  and  poles, 
modified  by  the  deflective  effect  of  the  earth's  rotation,  all  this 
explanatory  matter  has  a  strong  flavor  of  physics.  If  the  occur- 
rence of  plants  of  a  certain  kind  in  a  given  region  is  not  merely 
asserted,  but  is  shown  to  be  the  result  of  climatic  conditions  to 
which  the  plant  responds,  owing  to  its  sensitiveness  to  tempera- 
ture and  moisture,  this  closely  resembles  certain  chapters  of 
botany,  and  the  same  may  be  said  regarding  the  relation  of  animal 
distribution  to  zoology.  If  the  boundary  of  a  state,  the  location 
of  a  city,  or  the  industry  of  a  district  is  rationally  explained 
instead  of  empirically  stated,  the  explanation  is  of  a  kind  likely 
to  be  found  in  books  on  history  and  economics.  Shall  we  then, 
in  view  of  this,  relinquish  explanatory  treatment  to  other  subjects 
and  content  ourselves  with  empirical  statements  ?  Shall  we  adopt 
the  limitation  to  the  location  of  things,  as  above  suggested,  and 
thus  avoid  duplication  with  other  subjects  ?  No.  Duplication  is 
unavoidable  ;  and,  moreover,  it  is  reciprocal.  The  historian,  as 
well  as  the  botanist  and  the  zoologist,  must  borrow  from  the 
geographer  all  manner  of  facts  regarding  location,  extent,  distri- 
bution, climate,  form,  movements,  products,  populations,  and  so 
on ;  the  geologist  can  hardly  make  a  step  into  the  realm  of  the 
past  without  having  made  preparatory  study  of  the  present. 
Overlapping  and  duplication  are  unavoidable.  We  must  each  of 


20  EDUCATIONAL   ESSAYS 

us  try  as  far  as  possible  to  concentrate  upon  his  own  subject ; 
but  we  must  at  the  same  time  borrow  and  quote  with  the  utmost 
freedom  from  any  other  subject  that  will  give  us  aid  in  the  con- 
sideration of  our  own. 

Examples  of  Helpful  Duplication.  One  of  the  most  interest- 
ing fields  that  I  have  run  across  in  geographical  research  is  that 
open  common  where  geography  and  philology  overlap.  It  has 
often  been  remarked  that  the  Arabs  of  the  desert  have  many 
terms  for  sand  dunes,  evidently  because  they  are  familiar  with  the 
many  forms  that  sand  dunes  there  assume  ;  their  language  has 
developed  in  a  peculiar  direction  as  an  ontographic  response  to 
their  peculiar  physiographic  environment.  In  the  same  way  the 
people  of  the  Alps  have  various  terms  by  which  to  name  moun- 
tain summits  of  different  shapes;  this  is  another  ontographic  re- 
sponse to  a  peculiar  physiographic  environment.  But  there  are 
other  less  manifest  examples  of  a  somewhat  different  kind.  We 
treasure  as  a  fine  geographical  example  the  long  preservation  of 
ancient  forms  of  speech  in  remarkable  purity  in  Iceland,  an  out- 
of-the-way  island  ;  and,  by  way  of  contrast,  we  like  to  mention 
Malta,  an  island  that  is  very  much  in  the  way,  where  the  mingling 
of  peoples  has  resulted  in  the  mixture  of  Arabic  and  south-Euro- 
pean tongues.  We  have  already  called  attention  to  the  diffusion 
of  organic  forms  as  a  fundamental  ontographic  fact,  and  we  know 
that  variation  is  an  ontographic  consequence  when  diffusion  leads 
to  a  physiographic  environment  that  involves  separation  as  a 
result  either  of  distance  or  of  isolation.  As  examples  of  this  sort 
of  geographical  relation  we  may  point  either  to  the  several  species 
of  cassowaries  on  the  islands  of  Australasia,  or  to  the  several  races 
of  man  on  the  larger  divisions  of  the  lands,  —  where  barriers 
formed  by  the  oceans  are  supplemented  by  a  desert  barrier  in  the 
Sahara  and  by  a  mountain. barrier  in  the  Himalaya,  — or  to  the 
several  nationalities  in  Europe,  where  gulfs  and  barriers  are  so  im- 
portant. But  why  not  continue  this  line  of  inquiry,  and  instance, 
as  another  example  of  variation  following  on  diffusion  and  sepa- 
ration, the  differentiation  of  the  Romance  languages  from  Ru- 
mania to  Portugal,  and  thus  bring  in  the  interesting  story  of  the 
division  of  the  langue  d'oc  and  the  langue  d'oui  by  the  central  high- 
lands of  France  ?  Why  not  include  the  even  more  extraordinary 


CONTENT  OF   GEOGRAPHY  21 

story  of  the  words  "  pecuniary"  and  "  fee,"  which  have  come 
to  look  so  unlike  on  their  arrival  in  our  composite  language 
because  of  their  different  paths  of  travel  from  their  common 
source  ?  This  is  of  just  as  good  geographical  quality  as  is  the 
contrast  between  the  whites  and  the  blacks  in  our  southern 
states  ;  they  began  alike  somewhere  long  ago,  and  have  come  to 
be  different  through  long  ages  of  separation  before  they  are  again 
found  together,  —  and  separation  is  an  important  element  of 
physiographic  control. 

Not  only  speech  but  figures  of  speech  are  affected  by  physi- 
ographic environment.  Two  examples  of  this  are  found  among 
far-separated  maritime  peoples  who  were  so  impressed  by  the 
manner  in  which  a  boat  is  guided  by  its  rudder  that  they  both 
came. to  use  a  word,  which  primarily  meant  a  stick  and  second- 
arily a  stern  oar,  in  a  later  figurative  sense  meaning  the  guid- 
ance or  control  of  a  whole  people.  One  of  these  examples  is 
found  among  the  Scandinavians,  where  the  same  word  is  used 
in  "  the  helmsman  steers  the  boat  "  and  in  "  the  king  steers  the 
people";  here  the  original  and  the  figurative  meanings  of  the 
word  both  survive  to-day.  The  other  example  began  with  the  peo- 
ple of  the  eastern  Mediterranean  and  is  now  spread  through  all 
the  Romance  languages  and  the  Romance  element  of  English. 
French  still  preserves  the  original  sense  of  the  word  in  gouver- 
nail,  for  "rudder"  ;  but  we  have  lost  that  sense,  unless  perhaps  in 
a  passage  in  the  Bible  concerning  the  "  governor  "  (helmsman 
or  captain)  of  a  ship,  and  only  know  the  figurative  sense  :  the 
word  "govern"  is  therefore  a  long-lasting  response  to  an  early 
maritime  environment.  In  contrast  to  these  maritime  examples 
is  one  from  the  Arabian  desert:  a  missionary  has  told  me, —  in 
reply  to  the  question,  "What  is  the  Arab  word  for  '  govern,'  and 
what  is  its  origin?"  —"It  is  a  word  that  means  *  guide/  and  is 
derived  from  the  word  meaning  '  to  guide  a  horse.' '  In  all 
these  cases  it  is  as  legitimate  to  instance  the  effect  of  environ- 
ment on  language  as  to  instance  its  effect  on  industry. 

The  Practical  Value  of  defining  the  Content  of  a  Subject.  In 
occasional  conferences  with  different  geographers  on  sXich  ques- 
tions as  have  been  treated  in  this  essay,  I  have  gained  the  im- 
pression that  they  attached  relatively  little  value  to  abstract 


22  EDUCATIONAL  ESSAYS 

considerations,  and  that  it  sufficed  them  to  go  on  with  their 
work  without  inquiring  particularly  into  the  general  content  of 
the  subject  under  which  it  belonged,  and  without  attempting  to 
develop  what  may  perhaps  be  called  the  more  philosophical 
view  of  the  subject  as  a  whole.  There  was  a  time  when  I 
shared  this  indifference  to  abstract  inquiry  —  a  time  when  I  was, 
as  it  were,  overwhelmed  with  the  great  quantity  and  variety  of 
material  with  which  I  had  to  make  myself  more  or  less  familiar, 
and  when  there  seemed  to  be  no  more  need  than  there  was  occa- 
sion of  bringing  it  all  under  an  orderly  and  systematic  scheme. 
But  that  time  is  now -a  good  many  years  ago,  and  since  then  I 
have  passed  out  of  the  stage  of  life  in  which,  we  are  assured, 
our  original  work  is  to  be  completed,  and  have  entered  well  upon 
the  later  stage  in  which  the  contemplation  and  arrangement  of 
work  previously  done  is,  we  are  told,  more  attractive  than  the 
accomplishment  of  new  work.  It  is,  perhaps,  for  some  such  rea- 
son that  I  have  devoted  this  essay  to  the  content  of  geography  as 
a  whole,  because  I  am  persuaded  that  there  is  a  practical  value 
in  abstract  considerations  such  as  I  have  presented,  even  for 
younger  men,  and  that  if  a  general  scheme  of  work  in  accord- 
ance with  some  broad  and  philosophical  view  of  one's  chosen 
science  is  formulated  by  a  young  geographer  early  in  his  career, 
he  will  profit  greatly  from  it ;  for  he  will  thus  be  led  more  surely 
and  directly  to  detect  all  the  facts  that  are  pertinent  to  any  in- 
quiry he  may  enter  upon.  Such  a  scheme  is  always  open  to  modi- 
fication as  experience  increases.  If  the  geographer  undertakes 
field  study,  as  I  hope  he  may,  either  at  home,  where  there  is 
plenty  of  field  work  to  do,  or  abroad,  where  there  is  still  more  to 
be  done,  it  will  serve  him  well  to  know  as  definitely  as  possible  the 
essential  quality  of  the  work  before  him.  If  he  wishes  to  become 
an  all-round  geographer  and  to  give  a  thorough  geographical 
account  of  the  region  of  his  field  work,  he  will  be  greatly  aided 
in  keeping  his  eyes  open  to  the  facts  before  him  by  bearing  in 
mind  the  systematic  content  of  the  science  as  a  whole,  a  part  of 
which  he  proposes  to  study  in  the  region  he  has  selected. 


II 

THE  PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS 

Encouragement  from  Recent  Progress.  The  most  notable  char- 
acteristic of  the  condition  of  geography  in  the  schools  during 
recent  years  is  the  marked  improvement  that  it  has  experienced. 
The  improvement  accomplished,  and  still  in  progress,  is  most 
encouraging.  The  rate  of  advance  is  as  great  as  is  consistent 
with  sound  development.  Chief  among  the  impulses  toward  this 
march  of  improvement  in  geography,  as  in  various  other  school 
subjects,  have  been  the  reports  by  committees  of  specialists, 
particularly  those  published  by  the  National  Educational  Asso- 
ciation. These  reports  have  furnished  many  excellent  sugges- 
tions, which  superintendents  and  teachers  have  either  adopted 
or  discussed  ;  and  the  discussions  thus  excited  may  be  considered 
as  beneficial  to  the  subject  over  which  they  are  held  as  were 
the  improvements  that  were  immediately  adopted.  All  this  is 
most  gratifying.  Let  reports,  improvements,  and  discussions 
continue.  Geography  in  the  schools  will  thrive  on  them. 

Direction  in  which  Further  Progress  is  most  Needed.  There 
remains,  however,  much  to  be  done.  The  one  thing  which  would 
be,  above  all  others,  most  helpful  in  continuing  the  progress 
already  made,  is  the  development  of  a  higher  ideal  as  to  the 
content  of  geography  among  mature  students. 

Geography  is  too  generally  treated  as  an  Elementary  Study. 
It  is  a  singular  fact  that  there  are,  particularly  in  this  ambitious 
country,  very  few  students  of  geography  as  a  mature  subject. 
Most  persons  of  full  age  who  are  directly  concerned  with  geogra- 
phy are  engaged  in  presenting  its  supposed  elements  to  imma- 
ture pupils.  Very  few  are  engaged  in  developing  geography  for 
mature  students.  Very  few  mature  students  are  carrying  for- 
ward original  research  in  geography  of  a  grade  at  all  comparable 
to  the  research  now  so  generally  accomplished  in  various  standard 
mature  subjects.  How  many  original  investigators  in  geography 

23 


24  EDUCATIONAL   ESSAYS 

do  you  know  ?  Ask  the  same  question  concerning  physics 
and  chemistry,  geology,  botany,  and  zoology,  mathematics  and 
astronomy,  philology,  history,  and  literature,  and  make  note  of 
the  contrast  that  all  these  maturely  developed  subjects  present 
to  geography.  All  these  other  subjects  have  habitual  represen- 
tation in  our  colleges  and  universities.  Many  of  them  engage 
the  attention  of  professional  experts.  Geography  is  seldom  rec- 
ognized in  these  higher  educational  reaches.  Nor  are  there, 
except  rarely,  professional  positions  in  which  mature  geogra- 
phers are  employed  on  advanced  work.  There  are  truly  many 
topographers,  many  pilots,  many  clerks  in  post-offices  and  express 
companies,  many  officers  of  our  consular  service,  all  of  whom 
have  contact  of  one  kind  or  another  with  geography  ;  but  there 
are  very  few  professional  geographers,  deservedly  so  called.  It 
is  true  that  many  persons  travel  far  and  wide  over  the  world, 
and  some  of  them  write  very  entertaining  books  ;  but  travel  no 
more  makes  the  traveler  a  geographer  than  it  makes  him  a  botan- 
ist or  an  historian.  Mere  facts  of  occurrence  and  location  have 
about  the  same  rank  in  geography  that  words  have  in  literature, 
dates  in  history,  and  specific  names  in  botany  and  zoology.  A 
traveler's  narrative  is  no  more  a  geographical  work  because  it 
makes  mention  of  a  hill  and  a  harbor  than  it  is  a  botanical  work 
because  it  tells  something  about  a  forest  and  a  swamp.  It  is 
chiefly  among  the  small  body  of  explorers  that  we  find  mature 
geographers  ;  and  yet  not  all  of  these  brave  and  energetic  workers 
attempt  to  develop  the  more  scientific  aspects  of  geography. 
Explorers  are  generally  men  of  resolute  action  rather  than  of 
an  analytical  turn  of  mind,  and  they  too  often  have  about 
the  same  relation  to  mature  geography  that  collectors  of  wild 
animals  have  to  mature  zoology.  All  of  these  workers,  profes- 
sional and  amateur,  contribute  their  sheaves  of  fact  to  the  total 
gathering  of  geographical  knowledge,  but  the  facts  thus  gathered 
stand  in  need  of  discussion  and  coordination ;  the  sheaves  must 
be  threshed  and  winnowed.  The  advanced  workers,  seriously 
engaged  in  separating  the  grain  from  the  chaff  and  assorting 
the  grain  according  to  its  quality,  are  few  indeed. 

Illustration  from  Disputed  Botmdaries.    The  boundaries  be- 
tween nations  are  frequently  defined  in  terms  of  topographical 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        25 

forms,  and  one  might  expect  that  here  at  least  a  mature  under- 
standing of  geography  would  have  been  developed.  But  there 
are  two  recent  and  serious  disputes  regarding  boundaries  in 
which  the  misunderstandings  arise  directly  from  the  treatment 
of  topographical  features  in  an  elementary,  immature  manner. 
The  Argentine-Chilian  boundary,  as  verbally  denned  in  the  treaty 
of  1 88 1,  takes  no  account  of  the  possible  occurrence  of  valleys 
going  through  the  mountain  range,  so  as  to  predetermine  beyond 
chance  of  misunderstanding  the  course  of  the  boundary  in 
districts  where  the  continental  divide  departs  significantly  from 
the  crest  line  of  the  cordillera  of  the  Andes.  The  terms  of  the 
treaty  appear  to  have  been  based  on  the  antiquated  idea  that 
mountain  ranges  must  rise  between  river  basins,  and  that  rivers 
cannot  pass  through  mountain  ranges ;  an  idea  which,  as  Prince 
Krapotkin  has  shown,  has  long  worked  mischief  in  the  cartogra- 
phy of  Asia  by  placing  ranges  where  none  exist  and  by  omitting 
them  where  they  occur ;  an  idea  which  would  long  ago  have  dis- 
appeared from  geography  had  the  subject  been  maturely  and 
scientifically  developed. 

The  Alaskan  boundary,  as  verbally  defined  in  the  British- 
Russian  treaty  of  1825,  takes  no  such  account  of  the  possible 
complexity  of  mountain  form  and  irregularity  of  coasts  as  to 
preclude  misunderstandings  that  might  arise  with  respect  to  the 
summits  of  mountain  ranges,  or  with  respect  to  outer  and  inner 
shore -lines.  It  is  true  that  the  treaty  here  in  discussion  was 
made  three  quarters  of  a  century  ago  ;  yet  even  at  that  time  the 
occurrence  of  detached  and  discontinuous  ranges  and  of  irregu- 
lar coasts  was  perfectly  well  known,  and  it  would  seem  that  the 
commissioners  who  framed  the  treaty  might  have  avoided  all 
possible  ambiguity  had  they  based  their  definitions  on  a  more 
mature  study  of  topographical  forms.  I  do  not  propose  to  ex- 
press here  any  opinion  regarding  the  rights  in  either  of  these 
disputes,  but  only  to  call  attention  to  the  fact  that  the  disputes 
have  resulted  from  an  inadequate  comprehension  and  definition 
of  topographical  forms  ;  that  is,  from  the  employment  of  an  ele- 
mentary knowledge  of  geography  in  the  treatment  of  a  problem 
where  an  advanced  knowledge  would  have  been  much  more 
appropriate. 


26  EDUCATIONAL  ESSAYS 

Illustration  from  Immaturity  of  Geographical  Terminology. 
Any  subject  that  is  pursued  from  elementary  teaching  through 
secondary  and  collegiate  study  to  the  highest  reaches  of  inde- 
pendent investigation  is  always  accompanied  by  an  expanding 
terminology.  The  terms  that  suffice  for  the  beginner  do  not 
suffice  for  the  advanced  student.  It  is  true  that  the  terminology 
thus  developed  is  sometimes  of  an  embarrassing  fullness.  It  is 
sometimes  unnecessarily  detailed,  but  there  can  be  no  question 
that  it  is  on  the  whole  of  great  value.  It  is  well  that  the  spe- 
cialist should  be  cautious  about  introducing  new  terms ;  that  he 
should  test  his  inventions  by  home  use  before  offering  them  in 
print  to  his  colleagues.  It  is  true  also  that  of  the  total  number 
of  terms  invented  by  the  specialist  in  this  field  or  that,  many  per- 
ish, and  only  the  needed  ones  survive  in  general  scientific  use. 
If  it  were  possible  to  endow  all  specialists  with  so  much  wisdom 
that  they  could  foresee  the  needs  of  the  next  generation,  and 
invent  only  such  terms  as  would  prove  of  permanent  value,  much 
of  the  difficulty  that  is  inherent  in  the  question  of  terminology 
would  disappear ;  but  such  wisdom  is  not  granted  to  investiga- 
tors any  more  than  to  lawmakers.  All  that  can  be  expected  is 
that  each  individual  shall  work  carefully  and  honestly,  and  that 
the  processes  of  natural  selection  and  the  survival  of  the  fittest 
shall  operate  in  terminology  as  well  as  elsewhere.  The  develop- 
ment of  new  methods  and  the  discovery  of  new  results  make  the 
introduction  of  new  terms  inevitable.  A  good  name  is  of  great 
assistance  in  making  the  thing  named  more  generally  known. 
A  growing  terminology  is  characteristic  of  all  growing  sciences. 

In  reviewing  the  literature  of  geography  it  is  remarkable  to 
note  that  the  terminology  of  school  days  is  so  little  extended  in 
the  productions  of  mature  writers.  Consider,  for  example,  the 
subject  of  mountains.  Look  over  any  school  geography  and 
count  the  nouns  and  adjectives  that  are  used  with  a  technical 
meaning  in  the  chapter  on  this  subject ;  chain,  range,  peak, 
summit,  ridge,  pass,  are  among  them.  Now  look  over  the  best 
essay  that  can  be  found  in  which  a  mountainous  region  is  de- 
scribed by  a  mature  writer  for  mature  readers,  and  make  another 
count  of  the  same  kind.  The  adjectives  will  be  found  to  have 
"  grown  up  "  ;  that  is,  they  comprise  a  number  of  more  learned 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS   27 

words,  —  such  as  precipitous,  stupendous,  imposing,  formidable, 
—  yet  none  of  these  are  introduced  with  anything  like  technical 
definitions  :  they  are  used  in  a  general  literary  sense  such  as 
will  be  understood  by  the  polite  reader.  Among  the  nouns  there 
will  be  a  moderate  number  of  new  words,  most  of  which  are 
taken  from  the  local  patois  of  the  mountain  people,  or  from  the 
somewhat  colloquial  language  of  mountain  climbers  ;  but  there 
is  nowhere  any  sufficient  indication  that  these  new  words  are 
taken  from  a  systematic,  consistent,  and  thoroughgoing  termi- 
nology of  mountain  forms.  The  same  is  true  of  nearly  all  the 
other  divisions  of  geography.  Even  in  reports  so  important  as 
those  of  the  Mississippi  River  Commission,  certain  features  of 
the  great  river  and  its  flood  plain  go  practically  unnamed  and 
therefore  unnoticed.  The  small  number  of  technical  geograph- 
ical terms  that  have  been  introduced  by  a  few  writers  have  as 
yet  gained  little  general  currency. 

The  absence  of  a  mature  terminology  appropriate  to  mature 
geographical  descriptions  is  one  of  the  most  patent  signs  that 
geography  is  not  maturely  developed. 

Inattention  to  Mature  Geography  has  a  Bad  Effect  on  School 
Geography.  There  can  be  no  question  that  the  neglect  of  geog- 
raphy as  a  subject  for  mature  study  has  had  and  still  has  an 
injurious  effect  upon  the  condition  of  geography  in  the  schools. 
Special  emphasis  must  be  given  to  this  point,  for  it  is  not 
generally  enough  recognized.  One  may  attend  a  conference  of 
superintendents  and  teachers  before  whom  geography  is  a  sub- 
ject for  discussion,  and  hear  much  said  about  this  or  that  aspect 
of  the  subject,  about  this  or  that  device  for  its  presentation,  and 
yet  hardly  a  suggestion  may  be  made  to  the  effect  that  teachers 
of  geography  should  be  better  taught,  and  still  less  is  an  inti- 
mation offered  that  geography  itself  is  in  need  of  more  mature 
development  as  a  scientific  study.  It  is  not  in  our  own  country 
alone  that  this  complacent  attitude  prevails  :  recent  articles  by 
representative  foreign  authors  contain  practically  no  indication 
that  geography  in  the  schools  still  suffers  from  lack  of  prepara- 
tion on  the  part  of  the  teacher,  and  from  lack  of  advanced  work 
on  the  subject  in  the  universities.  These  deficiencies  are  less 
noticeable  in  continental  schools,  particularly  in  Germany,  where 


28  EDUCATIONAL  ESSAYS 

it  is  so  often  the  case  that  a  secondary  teacher  holds  the  degree 
of  doctor  of  philosophy  ;  but  they  are  certainly  serious  in  Great 
Britain,  where  geography  in  the  schools  is  a  very  commonplace 
study,  in  spite  of  the  enormous  importance  of  geography  to  the 
British  empire. 

Deficiency  of  Higher  Learning  in  Geography.  The  most  con- 
spicuous evil  consequence  of  this  state  of  things  is  the  want 
of  a  well-developed  body  of  higher  geographical  learning,  with 
respect  to  which  the  geography  in  the  schools  shall  stand  only 
as  a  beginning.  It  is  unfair  to  look  to  teachers  of  the  supposed 
elements  of  a  subject  for  the  development  of  its  more  advanced 
parts;  school-teachers  are  fully  occupied  with  duties  of  their 
own.  The  body  of  higher  learning  must  be  developed  in  geog- 
raphy as  it  has  been  in  other  subjects,  namely,  by  the  devoted 
work  of  specialists  who  give  their  best  thought  to  the  advance 
of  their  subject.  Many  specialists  in  other  sciences  are  profes- 
sors in  colleges  or  universities,  experts  in  governmental  bureaus, 
or  amateurs  of  high  intellectual  rank  ;  but  geography  is  seldom 
represented  in  this  goodly  company,  and  hence  the  development 
of  mature  geography  is  slow.  Many  subjects  that  make  their 
beginning  under  the  cover  of  geography  outgrow  their  shelter 
and  attain  an  independent  maturity.  Thus  astronomy,  geology, 
botany,  zoology,  history,  government,  and  economics  —  extracts 
from  whose  contents  are  first  introduced  into  school  work  along 
with  geography  —  gain  places  for  themselves  in  college,  while 
geography  disappears.  It  is  as  if  the  trunk  subject  had  subdi- 
vided, like  an  elm,  into  many  divergent  branches,  each  of  which 
flourishes  alone.  I  wish  the  simile  might  be  that  of  a  sturdy 
pine  whose  trunk  is  not  sacrificed,  however  many  limbs  it  gives 
forth.  There  can  be  little  question  that,  as  long  as  geography 
is  not  represented  in  colleges,  the  future  teachers  of  geography 
in  the  schools  will  be  insufficiently  educated  in  their  subject. 

Deficiency  of  Higher  Learning  discourages  High  Ideals.  In 
the  absence  of  a  mature  development  of  our  subject,  its  ideals 
must  be  of  a  low  order,  and  its  early  steps  can  make  only  un- 
certain progress  in  advancing  toward  an  unknown  goal.  What 
would  the  Latin,  the  geometry,  the  physics  of  our  schools  be 
if  those  subjects  had  no  representation  in  the  colleges  !  How 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        29 

definitely  the  first  steps  in  these  subjects  lead  toward  the  great 
body  of  their  higher  learning  !  How  greatly  would  the  geogra- 
phy of  the  schools  be  improved  if  geography  had  as  well  estab- 
lished a  place  in  our  colleges  as  history  has!  I  will  not  here 
take  up  the  question  whether  geography  is  entitled  to  so  uni- 
versal a  recognition.  Some  educators  may  think  it  is  not,  and 
certainly  the  existing  distribution  of  appointments  in  our  colleges 
would  confirm  that  opinion ;  but  it  may  be  safely  maintained 
that  if  a  professorship  of  geography  existed  in  every  college 
where  there  is  a  professorship  of  history,  our  ideals  as  to  the 
mature  content  of  geography  would  be  much  enlarged  above 
what  they  are  to-day,  and  our  conception  of  what  constitutes 
the  elements  of  the  subject  would  be  correspondingly  changed. 
We  should  at  least  be  cured  of  the  forlorn  idea  that  geography  / 
is  only  the  study  of  the  location  of  things. 

One  of  the  most  evident  results  of  the  immature  development 
of  geography  is  that  details  rather  than  principles  have  been 
dwelt  upon  in  school  work.  This  is  not  so  true  now  as  it  was 
twenty  years  ago,  but  it  is  still  too  often  true.  It  is  by  no  means 
always  the  fault  of  the  teachers.  It  may  be  due  in  large  part 
to  the  low  ideals  indicated  in  official  examination  papers,  for  if 
examinations  are  largely  directed  to  testing  a  knowledge  of  the 
innumerable  details  of  geography,  then  the  teacher  must  cram 
the  pupil,  and  cramming  trains  the  memory  rather  than  the  intel- 
ligence. On  the  other  hand,  if  emphasis  is  given;  both  in  teach- 
ing and  in  examinations,  to  general  principles  and  important 
relations,  under  which  items  are  adduced  simply  as  illustrations, 
then  the  intelligence  as  well  as  the  memory  is  developed.  Items 
of  occurrence  and  location  are  not  to  be  neglected,  but  they 
should  be  studied  in  their  natural  relations  instead  of  as 
isolated  facts. 

This  principle  is  now  pretty  generally  understood.  It  is  agreed 
that  a  cape,  a  river,  a  boundary,  a  city,  must  not  be  merely 
located  and  memorized,  and  then  set  aside,  unused,  unrelated 
to  anything  else ;  for  with  teaching  of  this  kind  the  essential 
spirit  of  geography  remains  dormant.  Yet  such  is  the  popular 
pressure  for  a  knowledge  of  the  names  and  places  of  things 
that  many  things  are  learned  merely  by  place  and  name.  It  is 


30  EDUCATIONAL  ESSAYS 

usually  held  to  be  necessary  to  go  briefly  over  a  large  number 
of  items,  even  if  there  is  no  time  to  learn  their  relations  without 
slighting  other  parts  of  the  subject ;  but  this  supposed  necessity 
is  open  to  question.  It  should  be  carefully  considered  whether 
the  names  that  are  learned  have  been  chosen  with  good  judg- 
ment from  among  the  countless  items  of  geography ;  whether 
they  are  really  chosen  at  all,  or  simply  inherited  from  a  time 
when  geography  had  not  reached  its  present  development ; 
whether  their  choice  is  made  with  due  regard  to  the  higher 
reaches  of  geography,  and  not  merely  in  obedience  to  a  poorly 
educated  public  sentiment  as  to  the  content  of  our  subject ;  and 
finally,  whether  items  should,  after  all,  be  given  so  much  promi- 
nence as  they  have  often  had,  with  the  result  of  subordinating 
the  large  principles  under  which  the  items  stand  only  as  indi- 
vidual examples. 

Value  of  Principles  versus  Items  illustrated  by  Geometry  and 
Physics.  A  possible  rearrangement  of  the  emphasis  on  items 
and  principles  in  geography  may  be  illustrated  by  reference  to 
the  actual  practice  in  geometry  and  physics.  No  good  teacher 
would  approve  of  memorizing  the  particular  figure  of  a  theorem 
in  geometry,  with  its  individual  proportion  of  parts,  its  attitude 
on  the  blackboard,  and  its  special  lettering,  as  a  means  of  learn- 
ing the  general  quality  of  the  theorem  that  the  figure  illustrates. 
It  is  the  generality  of  the  theorem  that  is  impressed ;  it  is  the 
possibility  of  applying  a  general  principle  to  any  particular  case' 
that  falls  under  it  that  must  be  emphasized  in  good  teaching. 
So  in  physics  ;  as  much  care  as  is  necessary  may  be  properly 
expended  on  the  construction  and  manipulation  of  a  piece  of 
apparatus,  but  the  emphasis  of  good  teaching  must  be  given  to 
the  principle  which  the  apparatus  is  used  to  illustrate.  I  believe 
that  it  is  possible  to  discover  and  establish  general  principles 
in  geography  likewise,  and  to  teach  individual  items  chiefly  as 
illustrations  of  the  principles  under  which  they  fall.' 

It  must  be  admitted,  however,  that  geometry  and  physics  are 
not  so  closely  analogous  to  geography  that  the  best  method 
of  study  in  the  first  two  is,  therefore,  the  best  in  the  third 
also.  The  lettering  of  a  chalk  figure  on  a  blackboard  and 
the  construction  of  a  piece  of  simple  apparatus  have  no  such 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        31 

importance  as  an  actual  village  in  a  valley  or  as  an  actual  island 
in  the  sea.  Nevertheless,  geographers  may  profit  by  taking  heed 
of  the  subordination  of  item  to  principle  in  geometry  and  physics ; 
they  may,  perhaps,  be  thus  aided  in  perceiving  the  proper  rela- 
tion of  the  specific  to  the  general  in  their  own  subject. 

Examples  of  Excessive  Detail  in  the  Study  of  Counties.  In 
illustration  of  excessive  attention  to  detail,  let  me  cite  certain 
official  examinations  that  have  sometimes  included  such  ques- 
tions as,  "  Name  the  counties  in  order  along  the  southern  border 
of  this  state."  Such  questions  have  been  defended  because  it 
is  held  to  be  desirable  that  every  inhabitant  of  a  state  should 
know  the  counties  into  which  his  state  is  divided  ;  but  this 
assumption  is  wide  open  to  doubt  when  it  is  seen  that  the  coun- 
ties cannot  be  learned  except  by  sacrificing  something  else.  It 
is  by  no  means  demonstrated  that  the  time  demanded  in  acquir- 
ing this  knowledge  has  been  used  to  the  best  advantage  by  the 
pupil.  Very  little  application  is  made  of  the  knowledge  after 
it  is  acquired.  It  would  be  interesting  to  inquire  of  pupils  thus 
trained  whether  the  list  of  counties  is  gladly  retained  in  the  mem- 
ory of  mature  years,  or  willingly  forgotten.  Surely,  if  forgot- 
ten, the  loss  does  not  impair  the  usefulness  of  a  citizen,  since 
the  forgotten  items  can  be  easily  regained  when  wanted.  There 
are  very  few  of  our  most  intelligent  friends  who  carry  in  their 
memories  such  items  as  the  names  and  relative  position  of  all 
the  counties  in  their  home  state  or  in  any  other  state,  and  it  is 
certainly  very  rarely  the  case  that  any  well-educated  man  or 
woman  regards  such  use  of  memory  as  a  measure  of  a  cultivated 
ihtelligence.  Truly,  something  about  counties  may  well  be  taught 
under  political  geography,  and  still  better  under  civics.  The  sub- 
division of  the  larger  counties  of  early  settlement  into  smaller 
counties,  as  population  grows,  deserves  mention  in  history ;  and 
the  unorganized  "  plantations  "  still  found  in  the  backwoods  of 
Maine  may  well  be  cited  as  examples  of  retarded  development, 
illustrating  to-day  a  condition  through  which  other  states  have 
long  ago  passed.  But,  as  a  matter  of  fact,  while  the  division  of 
a  state  into  counties  is  a  matter  of  practical  convenience  for 
various  purposes  of  record  and  administration,  the  actual  coun- 
ties into  which  a  state  is  divided  are  not  worth  memorizing  in 


32  EDUCATIONAL  ESSAYS 

competition  with  the  many  more  educative  problems  of  geog- 
raphy. If  counties  were  the  whole  content  of  geography,  we 
might  have  to  learn  them  all  over  the  country,  but  they  sink 
into  insignificance  in  comparison  with  many  other  matters  in  the 
actual  content  of  our  subject.  If  a  sheriff,  an  express  agent,  or 
a  postal  clerk  needs  to  know  the  counties,  of  a  state  (very  likely 
not  the  state  in  which  he  was  "  raised  "),  he  can  learn  them  at 
short  notice,  and  the  rest  of  us  can  get  along  very  well  by  look- 
ing up  any  particular  county  in  an  atlas  when  we  want  to  know 
something  about  it ;  and,  by  the  way,  the  habit  of  looking  up 
things  in  an  atlas  is  worth  the  memorized  lists  of  the  counties 
in  a  dozen  states.  Indeed,  in  some  respects  the  subdivision  of 
states  into  counties  is  outgrown ;  notably  with  regard  to  county 
prisons,  into  which  all  classes  of  local  malefactors  are  thrown, 
unclassified,  greatly  to  the  injury  of  many  of  them,  and  hence 
to  the  harm  of  the  community.  This  may  have  been  justifiable 
when  means  of  transportation  did  not  include  railroads,  but  it 
endures  to-day  in  the  more  closely  settled  states  only  as  the 
inheritance  of  an  earlier  condition  which  has  not  yet  changed 
into  appropriate  relation  to  its  new  environment. 

The  "  tier  of  counties"  question  is  probably  less  common 
now  than  it  used  to  be,  but  it  serves  to  illustrate  very  well  a  low 
ideal  as  to  the  content  of  geography  on  the  part  of  examination 
boards,  and  the  subordination  of  school  work  to  an  uneducated 
public  sentiment  that  demands  of  school  children  a  multitude 
of  details,  concerning  many  of  which  intelligent  persons  do  not 
regret  their  ignorance,  because  their  minds  are  occupied  with 
better  things.  While  the  low  ideal  exists,  the  work  of  the  teacheV 
and  the  examiner  must  lead  up  to  it.  When  the  ideal  as  to  the 
content  of  geography  is  raised,  school  work  will  rise  with  it  to 
a  higher  grade  than  it  now  reaches,  and  then  the  counties  of  a 
state  will  be  counted  among  the  "  honorable  points  of  ignorance." 

The  Three  Stages  of  Geographical  Development.  As  a  means 
of  leading  toward  higher  ideals,  let  me  now  attempt  to  show 
that  geography  as  a  mature  subject  is  capable  of  a  higher  de- 
velopment than  it  has  yet  reached.  In  this  connection  it  will 
be  well  to  review  briefly  the  three  stages  of  development  recog- 
nizable in  the  progress  of  our  venerable  subject.  Until  within 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        33 

about  a  hundred  years  the  content  of  geography  consisted  of  a 
body  of  uncorrelated  facts  concerning  the  earth  and  its  inhabit- 
ants. The  facts  were  described  empirically,  and  as  a  rule  very 
imperfectly.  Their  location  was  noted,  but.  their  correlations 
were  overlooked  ;  it  had  not,  indeed,  been  clearly  made  out  that 
correlations  existed.  This  blindly  inductive  first  stage  was  fol- 
lowed by  a  second  stage,  which  was  opened  by  Ritter's  exposi- 
tion of  the  relationship  between  the  earth  and  its  inhabitants. 
True,  Ritter  and  his  school  did  not  carry  the  idea  of  relationship 
systematically  through  all  parts  of  the  subject ;  and  such  rela- 
tionships as  were  noted  had  to  be  explained  on  the  old  doctrine 
of  teleology  —  the  adaptation  of  the  earth  to  man  —  instead  of 
on  the  modern  principle  of  evolution,  —  the  adaptation  of  all  the 
earth's  inhabitants  to  the  earth.  It  is  this  principle  which  char- 
acterizes the  third  stage  of  progress,  and  along  with  it  goes  a 
principle  of  almost  equal  importance  ;  namely,  that  all  the  items 
which  enter  into  the  relation  between  the  earth  and  its  inhabit- 
ants must  be  explained  as  well  as  described,  because  explana- 
tion aids  so  powerfully  in  observing  and  appreciating  the  facts 
of  nature.  It  should  be  noted  that  the  two  great  advances  by 
which  the  third  stage  of  geographical  progress  is  set  forward 
from  the  second  are  the  contributions  of  others  than  geographers  : 
the  principle  of  organic  evolution  is  owed  to  the  biologists  ;  the 
principles  under  which  explanation  is  found  for  the  features  of 
the  earth  are  owed  chiefly  to  astronomers,  physicists,  and  geolo- 
gists. This  indebtedness  might  not  have  been  so  heavily  con- 
tracted if  the  geographers  of  the  older  school  had  been  less 
content  with  a  purely  inductive  treatment  of  their  subject ;  if 
they  had  asked  themselves  not  only  where  and  what,  but  also 
how  and  why  things  are  as  we  find  them. 

The  Content  of  Modern  Geography.  Geography  has  to-day 
entered  well  upon  its  third  stage  of  progress.  The  "  causal 
notion  "  is  generally  admitted  to  be  essential  in  the  study  of  the 
relation  of  the  earth  and  its  inhabitants.  Thus  understood,  geog- 
raphy involves  the  knowledge  of  two  great  classes  of  facts  :  first, 
all  those  facts  of  inorganic  environment  which  enter  into  relation- 
ship with  the  earth's  inhabitants  ;  second,  all  those  responses  by 
which  the  inhabitants,  from  the  lowest  to  the  highest,  have 


34  EDUCATIONAL  ESSAYS 

adjusted  themselves  to  their  environment.  The  first  of  these 
classes  has  long  been  studied  as  physical  geography,  although 
this  name  has  been  used  as  a  cover  for  many  irrelevant  topics. 
In  recent  years  there  has  been  a  tendency  to  compress  the  name 
into  the  single  word  "  physiography." 

The  second  of  the  two  classes  of  facts  has  not  yet  reached  the 
point  of  being  named,  but  perhaps  it  may  come  to  be  called 
ontography.  Ecology,  to  which  increasing  attention  is  given  by 
biologists,  is  closely  related  to  what  I  here  call  ontography,  yet 
there  is  a  distinction  between  the  two,  in  that  ecology  is  con- 
cerned largely  with  the  individual  organism,  while  ontography  is 
intended  to  include  all  pertinent  facts  in  structure,  physiology, 
individual,  and  species. 

Neither  physiography  nor  ontography  alone  is  geography 
proper,  for  geography  involves  the  relation  in  which  the  ele- 
ments of  its  two  components  stand  to  each  other.  Each  of  the 
components  must  be  well  developed  before  geography  can  be 
taken  up  as  a  mature  study. 

The  relations  involved  in  geography,  as  thus  understood,  are 
of  the  most  varied  nature.  A  relation  that  has  been  frequently 
quoted  since  Ritter  first  called  attention  to  it  is  the  one  between 
the  irregularity  of  continental  coast  lines  and  the  stage  of  human 
development ;  but  a  continuous  series  may  be  made  from  this 
large  and  general  relation  to  such  trifling  matters  as  the  relation 
that  determines  the  point  where  a  common  road  bridges  a  stream. 
Evidently,  then,  it  is  not  the  dimensions  of  the  relation  that 
determine  its  geographical  quality,  although  its  dimensions  may 
have  much  influence  in  fixing  the  stage  at  which  it  may  be  profit- 
ably introduced  in  school  work,  and  the  emphasis  that  is  to  be 
given  to  it  there.  Oceans,  lofty  mountain  ranges,  and  deserts 
are  formidable  barriers  that  oppose  the  migration  of  plants  and 
animals  ;  but  from  these  great  controls  over  the  movement  of 
whole  species  and  races  a  continuous  series  of  examples  might 
be  made,  leading  down  to  the  control  that  a  hill  slope  exerts 
over  the  direction  of  a  plow  furrow. 

It  is  not  only  to  the  inorganic  parts  of  the  earth  that  man  is 
related,  but  to  the  organic  parts  as  well.  It  is  the  scarcity  of 
plant  and  animal  food  that  limits  the  human  population  of  deserts, 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        35 

just  as  it  is  the  aridity  of  climate  that  limits  the  number  of  desert 
plants  and  animals.  It  is  the  density  of  forest  growth  under 
equatorial  rains  that  has  made  some  of  the  savage  natives  of 
New  Guinea  expert  canoe  men  :  the  rivers  there  are  more  avail- 
able as  highways  than  the  plant-crowded  land.  The  relation  of 
population  and  industries  to  the  cotton,  corn,  and  wheat  crop  of 
the  United  States  is  a  standard  geographical  problem.  More- 
over, while  attention  was  formerly  given  in  largest  part  to  the 
relation  of  the  earth  to  man,  and  while  this  still  seems  properly 
enough  to  characterize  the  more  elementary  stages  of  geography, 
a  large  share  of  attention  in  its  mature  stages  must  be  given  to 
the  relation  of  the  earth  to  all  kinds  of  life,  and  to  the  interre- 
lations of  all  kinds  of  life  in  so  far  as  they  involve  considera- 
tions of  place  and  space.  Cattle  are  excluded  from  certain  parts 
of  Africa  by  the  tsetse-fly ;  this  is  as  good  geography  as  is  the 
relation  of  the  Gaelic  and  English  languages  to  the  Highlands 
and  Lowlands  of  Scotland.  Man  was  once  looked  upon  as  set 
apart  from  the  rest  of  organized  beings,  but  this  is  no  longer 
possible.  The  devices  that  he  has  employed  and  the  battles  that 
he  has  fought  in  gaining  his  present  place  resemble,  more  than 
they  differ  from,  those  by  which  all  plants  and  animals  have 
gained  their  places.  Indeed,  it  is  but  the  commonplace  of  com- 
parative zoology  to-day  to  see  in  man  a  great  number  of  struc- 
tures and  processes  that  have  been  inherited  from  a  time  when 
he  was  not  man ;  and  many  of  these  structures  .and  processes 
are  responses  to  his  physical  environment. 

A  science  cannot  be  cut  off  arbitrarily  in  the  midst  of  a 
continuous  series  of  relations  that  characterize  it.  Geography 
must  consider  the  ontography  of  the  lowest  beings  as  well  as 
of  the  highest.  It  should  therefore  be  our  effort,  in  giving  to 
geography  a  mature  development,  to  open  our  conception  of  its 
content  as  widely  as  possible,  rather  than  to  set  narrow  limits 
to  it  ;  to  probe  all  the  elements  of  physical  environment  and 
all  the  manifestations  of  life  in  order  to  discover  examples  V 
of  relations  that  have  thus  far  been  overlooked.  Only  when 
geography  is  thus  more  fully  constituted  a  mature  subject  will 
it  be  possible  to  make  the  best  selection  of  those  parts  which 
may  be  considered  elementary ;  only  through  the  development 


36  EDUCATIONAL  ESSAYS 

of  the  higher  reaches  of  the  subject  can  the  lower  reaches  be 
best  ordered.  It  is  for  this  reason  that  these  somewhat  tran- 
scendental considerations  deserve  the  attention  of  thoughtful 
and  progressive  teachers. 

The  Unity  of  Geography.  It  is  especially  the  factor  of  relation- 
ship of  earth  and  inhabitants  that  characterizes  geography  as  a 
subject  apart  from  other  sciences,  and  that  gives  an  essential 
unity  of  content  and  discipline  to  all  its  varied  parts.  Objection 
has  been  made  to  geography  because  of  its  composite  nature  ;  it 
has  been  reproached  with  being  only  a  patchwork  of  scraps  from 
many  other  subjects,  without  any  essential  quality  of  its  own. 
These  assertions  do  not  seem  to  me  to  have  force  :  in  the  first 
place,  because  other  subjects  as  well  as  geography  are  composite 
if  they  are  judged  only  by  the  things  that  they  treat,  and  by  the 
processes  employed  in  their  study ;  and,  in  the  second  place, 
because  geography,  properly  understood,  has  as  well  defined  an 
essence  of  its  own  as  other  subjects  have. 

It  is  perfectly  true  that  the  geographer,  even  the  young  geog- 
rapher, must  learn  something  of  the  planets  in  connection  with 
his  study  of  the  earth -as  a  globe,  something  of  the  behavior  of 
gases  in  connection  with  his  study  of  the  atmosphere,  something 
of  the  history  of  the  earth  in  connection  with  his  study  of  land 
forms,  something  of  the  structure  of  plants  and  animals  in  con- 
nection with  the  ontographical  half  of  his  subject ;  but  it  is  no 
less  true  that  the  astronomer  must  learn  something  of  the  earth 
as  a  globe  in  connection  with  his  study  of  the  planets,  the  physi- 
cist must  learn  something  of  the  atmosphere  in  connection  with 
his  study  of  gases,  the  geologist  must  learn  something  of  exist- 
ing land  forms  in  connection  with  his  study  of  the  past  history 
of  the  earth,  the  biologist  must  learn  something  of  the  lands  and 
the  seas  in  connection  with  his  studies  of  plants  and  animals. 
/One  is  tempted  to  say  that  all  things  seem  to  be  shared  by  all 
/sciences,  and  that  each  science  can  be  defined  only  in  terms  of 
'the  relation  in  which  it  studies  things,  rather  than  in  terms  of 
-'  the  things  that  it  studies.  The  geographer  learns  what  he  wishes 
to  know  about  the  earth  as  a  globe,  even  though  this  chapter  of 
his  study  may  be  related  to  astronomy ;  about  the  atmosphere, 
even  though  he  may  divide  this  part  of  his  subject  with  the 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        37 

physicist ;  about  plants  and  animals,  even  if  this  seems  to  be 
a  trespass  on  biology ;  but  finally  he  strings  all  the  things  he 
has  learned  on  the  thread  of  the  relation  between  earth  and  life. 
The  unity  of  consideration  thus  gained  warrants  the  inclusion  of 
all  these  things  under  his  subject  of  study,  and  it  gives  us  a  right 
to  consider  the  subject  of  study  as  a  science  unit. 

The  Complexity  of  Geography.  It  should  be  no  reproach  to 
geography  that  it  is  concerned  with  a  large  variety  of  things, 
some  of  which  are  treated  elsewhere,  for  the  same  may  be  said 
of  all  the  other  sciences.  Every  material  thing  that  is  studied 
by  the  geographer  is  also  fit  for  study  by  the  chemist  and  the 
physicist.  The  chemist  may  wisely  inquire  into  the  nature  of  the 
elements  and  compounds  that  are  found  in  minerals,  plants,  and 
animals.  The  physicist  may  advisedly  study  the  physical  proper- 
ties of  these  things  and  the  forces  by  which  they  interact.  If  the 
chemist  and  the  physicist  study  in  their  laboratories  rather  than 
outdoors,  this  is  only  because  they  are  more  interested  in  system- 
atic than  in  regional  physics  and  chemistry ;  in  the  establish- 
ment of  general  laws  than  in  the  record  of  individual  occurrences. 
The  weathering  of  a  rock  surface,  the  fall  of  a  rock  fragment 
from  a  cliff,  are  processes  that  come  under  the  laws  of  chemistry 
and  physics  ;  but  the  chemist  and  the  physicist  do  not  trouble 
themselves  especially  about  the  innumerable  repetitions  of  these 
processes  in  nature  ;  they  are  satisfied  with  establishing  the  laws 
that  generalize  the  processes,  and  with  good  reason,  as  I  shall 
show  further  on. 

It  should  surely  be  no  reproach  to  the  mature  geographical 
investigator  that  he  must  study  many  kinds  of  things,  and  that 
he  must  share  many  subjects  with  other  sciences,  for  all  this  is 
equally  true  of  the  geologist  and  the  historian.  The  geologist 
must  know  much  of  chemistry  and  of  physics,  much  of  geogra- 
phy and  of  biology  ;  but  he  strings  all  his  facts  on  a  single  thread, 
the  sequence  of  events  in  the  earth's  history,  and  thus  arranged 
they  belong  to  geology.  The  historian  must  know  all  manner 
of  things  in  the  realms  of  geography,  language,  and  economics, 
and  he  would  do  well  to  know  something  of  biology  if  he  would 
really  appreciate  many  of  man's  motives ;  but  all  the  facts  that 
he  gathers  are  to  be  arranged  so  as  to  exhibit  the  sequence  and 


38  EDUCATIONAL  ESSAYS 

relationship  of  events  in  human  progress,  and  thus  arranged  they 
belong  to  history. 

Not  only  do  Other  sciences  resemble  geography  in  gathering 
their  items  from  many  fields  of  knowledge,  but  like  geography 
they  employ  many  methods  in  reaching  their  results.  If  geogra- 
phers must  follow  the  methods  of  the  astronomer  in  order  to 
understand  the  earth  as  a  globe,  of  the  physicist  in  order  to 
appreciate  climatic  factors,  of  the  geologist  in  order  to  under- 
stand land  forms,  of  the  biologist  in  order  to  apprehend  the 
responses  of  living  beings  to  their  environment,  they  are  neither 
peculiar  nor  unfortunate  in  this  breadth  of  exercise.  The  as- 
tronomer has  long  had  to  use  mathematics,  yet  astronomy  is 
not  mathematics,  and  mathematics  is  not  astronomy.  In  recent 
years  the  astronomer  has  had  to  learn  much  of  physics  and 
chemistry,  yet  no  one  thinks  of  confusing  these  well-defined 
sciences  on  that  account.  Changes  of  color  on  Mars  with  his 
change  of  seasons  suggest  that  the  astronomer  will  soon  have  to 
borrow  something  from  the  biologist ;  so  much  the  better  if  he 
does,  and  we  may  be  sure  that  both  astronomy  and  biology  will 
thrive  under  the  new  regime.  The  chemist  constantly  employs 
the  methods  of  the  physicist  and  the  mathematician ;  like  every 
one  else,  he  uses  language  to  express  his  thoughts,  although 
language  is  the  special  study  of  the  philologist ;  and  he  must 
follow  accurate  processes  of  thought  if  he  would  reach  good 
results,  even  though  the  processes  of  thought  are  the  special 
province  of  the  logician. 

In  view  of  these  comparisons  it  does  not  seem  to  me  that 
geographers  need  fear  that  their  subject  is  so  complex  as  to  be 
in  danger  of  disintegrating,  provided  they  give  heed  to  its  in- 
tegrating essence.  Geography  is  complex,  like  other  sciences ; 
but,  like  other  sciences,  geography  is  unified  by  the  continuity  of 
its  essential  quality  through  all  its  varied  parts.  Possibly  geogra- 
phy is  the  most  complex  of  all  sciences  —  some  one  science  must 
stand  at  the  head  of  the  list  in  this  respect,  but  it  must  therein 
differ  only  in  degree,  not  in  kind,  from  its  fellows ;  and  it  is  yet 
to  be  shown  that  complexity  is  not  an  attractive  advantage  in 
leading  the  student  along  many  profitable  lines  of  thought,  in- 
stead of  a  deterring  disadvantage. 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS   39 

The  Limits  of  the  Sciences.  Although  one  may  be  at  some 
pains  to  indicate  the  limits  by  which  his  science  is  reasonably 
bounded,  it  does  not  follow  that  he  must  hold  himself  too  narrowly 
within  these  limits.  Truly,  the  astronomer  is  chiefly  concerned 
with  the  heavenly  bodies,  but  he  is  welcome  to  come  down,  if  he 
wishes,  to  things  terrestrial,  and  to  define  the  boundary  of  Colo- 
rado in  terms  of  astronomical  quantities ;  but  he  might  as  con- 
sistently consider  himself  responsible  for  the  explanation  of  plant 
growth  during  the  season  when  the  sunshine  is  long  and  strong. 
The  boundary  of  Colorado  by  meridians  and  parallels  is  as  truly 
a  geographical  matter,  as  truly  .a  response  to  physical  environ- 
ment, as  is  the  settlement  of  a  colony  at  a  protected  bay  head,  or 
the  building  of  a  beaver  dam  in  the  open  valley  of  a  small  stream. 

The  geologist  may,  if  he  so  desire,  supplement  his  historical 
account  of  the  formation  of  the  lake  Superior  iron  ores,  of  the 
telluric  forces  by  which  the  ore  bodies  were  deformed,  and  of 
the  erosion  by  which  they  were  laid  bare,  with  a  consideration  of 
the  modern  times  of  discovery  and  exploitation,  and,  in  order  to 
impress  his  students  with  the  richness  and  magnitude  of  the  ore 
deposits,  he  may  explain  how  they  have  led  to  the  development 
of  great  business  undertakings ;  and  he  is  perfectly  welcome  thus 
to  overrun  the  fields  of  geography,  history,  economics,  metal- 
lurgy, and  so  on.  The  physicist  may  exemplify  the  laws  of  gases 
by  explaining  the  heat  and  dry  ness  of  the  chinook  wind,  or  he 
may  illustrate  the  laws  of  fluids  in  a  discussion  of  the  waves  of 
the  sea  ;  but  the  winds  and  the  waves  are  none  the  less  elements 
of  geographical  environment.  The  historian  is  welcome  to  intro- 
duce as  much  geology  and  geography  as  he  desires  into  his  ac- 
count of  the  promontories  and  bays  of  Greece ;  the  wonder  is, 
indeed,  that  he  does  not  do  so  more  freely  than  is  to-day  habitual ; 
he  is  certainly  warranted  in  explaining  the  steam  engine,  the 
Bessemer  process  of  making  steel,  and  the  various  applications 
of  electricity  as  events  of  high  importance  in  the  progress  of  the 
last  century  and  a  half ;  and  he  is  fully  justified  in  giving  some 
account  of  the  principles  of  organic  evolution,  because  they  have 
so  profoundly  modified  philosophical  and  religious  thought  in  the 
last  third  of  a  century.  Surely,  all  these  things  are  as  pertinent  to 
the  history  of  man  as  are  the  revolutions  of  a  more  military  sort. 


40  EDUCATIONAL  ESSAYS 

It  is,  however,  a  significant  fact  that  astronomers  do  not  find 
time  to  tell  anything  about  the  boundary  of  Colorado ;  they  are 
too  much  occupied  with  their  own  affairs  to  take  up  geographical 
problems.  Geological  text-books  have  no  pages  to  spare  for  the 
history  of  the  development  of  iron-ore  mining  around  lake  Supe- 
rior ;  they  have,  indeed,  hardly  pages  enough  to  tell  all  that  is 
desirable  as  to  the  origin  of  the  ores.  It  is  only  in  the  largest 
volumes  of  history  that  space  is  found  for  accounts  of  the  inven- 
tions that  have  revolutionized  the  modern  world,  although  these 
inventions  are  quite  as  pertinent  to  the  subject  of  history  as  are 
the  tactics  of  a  general  on  a  battle-field.  As  a  matter  of  fact, 
such  subjects  as  astronomy,  geology,  and  history  are  so  rich  in 
materials  and  so  well  organized  in  methods  that  they  are  sel- 
dom tempted  to  run  over  other  fields  than  their  own ;  and  it  is 
to  this  condition  of  abundant  material  and  well-organized  method 
that  I  hope  to  see  geography  advance.  The  geographer  may,  if 
he  wishes,  tell  about  the  individual  features  of  other  planets  than 
the  earth ;  but  there  is  so  much  to  say  about  the  earth  as  a 
globe  that  everything  about  the  other  planets  must  be  excluded 
that  does  not  aid  the  study  of  our  own  planet.  He  may  turn 
back  from  the  present  to  the  past,  and  describe  the  results  of 
many  geological  discoveries  ;  but  it  is  unwise  to  do  so  unless 
these  discoveries  bear  immediately  on  present  geographical  con- 
ditions. He  may  feel  tempted  to  explain  the  principles  of  sys- 
tematic botany  and  zoology,  and  to  enlarge  upon  the  facts  of 
history;  but  in  so  far  as  these  excursions  lead  him  into  fields 
that  are  outside  of  geographical  relationships,  he  had  better 
avoid  them,  not  because  such  excursions  are  uninteresting  or 
unprofitable  in  themselves,  but  because  they  take  time  that 
can  ill  be  spared  from  geographical  duties.  I  hope  to  see  the 
teacher  of  geography  spend  his  time  as  carefully  as  the  teacher 
of  geometry  or  of  chemistry  does.  Let  him,  by  all  means, 
enrich  his  subject  by  introducing  all  manner  of  pertinent  illus- 
trations ;  let  him  show  an  intimate  acquaintance  with,  and  a 
warm  sympathy  for,  all  the  sciences,  but  let  him  be  jealous  of 
unwarranted  infringements  upon  the  hours  allotted  to  his  own 
science,  and  earnest  in  preserving  its  integrity.  Under  such  a 
teacher  no  student  will  complain  that  the  content  of  geography 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS   41 

is  so  complex  and  its  methods  are  so  diverse  that  it  has  neither 
unity  nor  discipline. 

Systematic  and  Regional  Geography.  The  attention  given  to 
general  principles  and  to  specific  items  differs  greatly  in  the 
different  sciences.  One  reason  for  this  is  that  some  sciences  are 
concerned  chiefly  with  the  abstract  relations  or  the  general  prop- 
erties of  things,  while  others  are  more  concerned  with  the  things 
themselves.  Another  reason  is  that  in  some  sciences  a  principle 
or  a  category  of  phenomena  may  be  exemplified  by  a  great  num- 
ber of  instances,  and  here  a  large  share  of  attention  is  given  to 
the  general  principles  under  which  the  instances  may  be  grouped ; 
while  in  others  the  number  of  illustrative  instances  is  small,  and 
here  attention  is  given  chiefly  to  individual  things. 

Geometry  and  algebra  are  not  concerned  with  things  at  all, 
but  only  with  the  relation  of  the  forms  and  the  quantities  of 
things.  Their  methods  are  characteristically  abstract,  mental, 
deductive,  and  their  resort  to  diagrams  and  equations  is  only  as 
an  aid  to  the  memory.  All  their  demonstrations  could  be  per- 
formed with  the  eyes  shut,  in  the  dark,  if  memory  sufficed  to 
follow  the  necessary  operations  through  the  successive  steps  that 
lead  to  the  result.  Specific  instances,  as  in  diagrams  and  equa- 
tions, are  of  value  only  as  illustrations  of  general  principles,  as 
has  already  been  stated.  Geometry  and  algebra  are  therefore 
systematic  and  universal  instead  of  being  local  or  regional ;  they 
have  no  necessary  association  with  any  special  place  or  time. 

Physics  and  chemistry  deal  with  the  properties  and  relations 
of  matter ;  they  necessarily  study  individual  specimens  of  matter, 
but  this  is  in  order  to  gain  results  of  general  application.  They 
adduce  specific  instances  as  examples  of  general  principles  ;  but 
no  one  would  think  of  attempting  to  teach  the  physics  and  chem- 
istry of  Minnesota,  for  example,  although  Minnesota  is  full  of 
matter  and  energy ;  there  is  not  enough  of  local  quality  to  make 
the  physics  and  chemistry  of  a  state  worth  considering  apart 
from  the  physics  and  chemistry  of  the  world. 

Zoology  and  botany  are  concerned  with  things  ;  yet  the  effort 
of  the  zoologist  and  botanist  is  to  generalize,  both  as  to  the  form 
and  growth  of  the  individual  and  as  to  the  development  of  the 
race  or  species.  Thus  systematic  zoology  and  systematic  botany 


42  EDUCATIONAL  ESSAYS 

(meaning  by  these  phrases  not  merely  the  study  of  classifica- 
tion, but  also  of  individual  growth  and  of  racial  development 
as  far  as  they  are  generalized)  attain  a  high  importance.  On 
the  other  hand,  the  individual  and  the  grouping  of  individuals 
attract  attention,  because  plants  and  animals  are  not  uniformly 
spread  over  the  world.  Regional  zoology  and  regional  botany 
thus  gain  an  importance  that  has  no  likeness  in  mathematics, 
physics,  or  chemistry. 

Astronomy  is  largely  specific,  particularly  so  with  regard  to 
bodies  like  planets,  of  which  but  few  examples  are  known ;  yet 
classification  and  the  establishment  of  general  principles  are 
attempted  whenever  possible,  as,  for  example,  in  the  grouping 
together  of  stars  according  to  their  proper  motion,  their  paral- 
lax, or  their  spectrum  ;  or  in  the  demonstration  that  the  planets 
move  around  the  sun  in  ellipses.  The  long  duration  and  the  sys- 
tematic movements  of  most  of  the  things  studied  in  astronomy 
give  the  individuals  a  greater  importance  than  is  attained  by 
biological  individuals ;  for  the  extremely  small  size,  the  brief 
existence,  and  the  unpursuable  movements  of  many  organic 
forms  turn  attention  from  the  individual  to  the  species. 

When  we  come  to  geography,  its  traditional  treatment  is 
found  to  be  very  largely  specific,  as  has  been  already  indicated. 
The  establishment  of  categories,  under  which  related  phenomena 
are  brought  together,  is  seen  in  the  use  of  such  elementary 
terms  as  "river,"  "coast,"  "harbor,"  "city,"  and  so  on ;  but 
the  well-recognized  categories  are  few  in  number  compared  to 
those  established  in  botany  and  zoology,  and  many  of  the  cate- 
gories are  of  so  general  a  nature  that  they  do  not  suffice  to 
indicate  clearly  the  characteristic  features  of  the  things  that  are 
brought  under  them.  Moreover,  it  is  so  common  to  give  a  large 
share  of  attention,  as  has  already  been  pointed  out,  to  such 
items  as  name  and  location  that  many  a  pupil  must  fail  to  appre- 
ciate the  general  relations  of  the  examples  that  he  studies.  In 
a  word,  systematic  geography  is  very  poorly  developed,  while 
specific  or  regional  geography  is  overgrown  although  incomplete. 
This  is  as  if  the  botanist  gave  little  attention  to  the  kinds  of 
plants  that  grow  on  the  earth,  and  devoted  most  of  his  attention 
to  the  place  of  occurrence  of  his  vaguely  defined  genera. 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        43 

I  therefore  invite  special  attention  to  the  need  of  developing, 
as  maturely  as  possible,  the  systematic  side  of  geography,  as 
one  of  the  means  of  most  effectively  improving  the  condition  of 
geography  in  the  schools. 

Systematic  Geography  is  concerned  with  the  kinds  of  relation- 
ships that  exist  between  the  earth  and  its  inhabitants.  The 
actual  relationships  are  countless ;  the  different  kinds  of  rela- 
tionships are  very  numerous,  although  less  numerous  than  the 
relationships  themselves.  The  number  of  kinds  is  so  great  that 
it  is  highly  desirable  to  arrange  them  according  to  some  scheme 
of  classification,  so  that  similar  kinds  of  relationships  may  be 
brought  into  near  association  with  one  another,  while  unlike 
relationships  may  be  set  farther  apart.  It  thus  becomes  essen- 
tial to  analyze  the  relations  into  the  elements  that  are  related, 
and  to  divide  these  elements  into  as  many  categories  as  may  be 
needful,  and  then  to  classify  these  categories.  By  no  other 
method  can  confusion  be  avoided  in  a  subject  so  large  as  that 
with  which  we  are  concerned.  I  therefore  propose  to  outline 
here  some  of  the  chief  systematic  divisions  of  the  two  parts  of 
our  subject,  and  to  point  out  in  particular  certain  divisions 
whose  systematic  arrangement  is  not  yet  generally  agreed  upon. 

Systematic  Physiography.  The  four  chief  divisions  of  physi- 
ography are  the  earth  as  a  globe,  the  atmosphere,  the  oceans, 
and  the  lands  ;  but  the  content  and  the  order  of  presentation  of 
these  divisions  vary  in  different  books,  and  a  fifth  division,  the 
distribution  of  plants  and  animals,  is  added  by  some  writers. 
This  addition  may  be  defended  on  various  grounds  in  elementary 
study,  but  it  is  always  open  to  the  serious  objection  that  it 
involves  an  essentially  regional  treatment,  and  that  it  therefore 
belongs  with  the  regional  study  of  the  continents  and  their 
physical  subdivisions  rather  than  with  the  general  study  of  the 
categories  into  which  the  physical  features  of  the  earth  are 
divided.  It  remains  to  be  determined  by  experiment  whether  it 
would  not  be  more  useful  to  limit  the  proposed  fifth  division  to 
a  systematic  consideration  of  the  physiographic  factors  by  which 
the  distribution  of  plants  and  animals  is  controlled,  and  to  place 
the  study  of  organisms,  in  so  far  as  it  is  geographical,  under 
ontography  or  under  regional  geography. 


44  EDUCATIONAL  ESSAYS 

Further  subdivision  of  systematic  physiography  varies  greatly 
with  different  authors,  as  may  be  illustrated  by  a  brief  con- 
sideration of  the  treatment  of  the  lands.  The  older  writers 
gave,  as  a  rule,  insufficient  attention  to  this  division  of  the  sub- 
ject, but  this  defect  is  now  in  process  of  rapid  correction.  Yet, 
although  the  different  kinds  of  land  forms  are  gaining  an  in- 
creasing attention  in  the  newer  text-books,  the  plan  of  subdivi- 
sion of  this  large  and  important  heading  is  not  yet  agreed  upon. 
I  venture,  therefore,  to  offer  for  consideration  the  following  out- 
line of  a  scheme  for  its  mature  treatment : 

1.  The  general  features  of  the  lands  as  contrasted  with  those  of  the 
atmosphere,  the  ocean,  and  the  ocean  bottom.    The  weathering  and  wash- 
ing of  the  land  surface  and  the  attack  of  the  sea  on  the  land  border  result 
in  slow  changes  of  form.    Branching  valley  systems,  draining  to  the  sea; 
are  the  most  characteristic  signs  of  these  changes.    The  long  continuation 
of  the  destructive  changes  must  result  in  the  reduction  of  any  land  surface, 
however  high  and  uneven  at  first,  to  a  low,  featureless  plain,  close  to  sea 
level ;  and  every  example  of  land  form  must  stand  somewhere  in  the  cycle 
of  systematic  changes  which  end  in  the  plain  of  degradation. 

2.  The  lands  may  be  more  specifically  treated  under  three  headings : 
(#)  land  forms  of  various  structures,  and  in  various  stages  of  the  process  of 
sculpture  ;   (£)  streams  by  which  the  sculpture  is  controlled,  here  including 
glaciers  as  a  climatic  variant  of  water  streams  (winds,  active  in  desert 
regions,  have  already  been  treated  under  the  atmosphere  ;  waves  and  cur- 
rents, active  along  the  land  margin,  have  been  treated  under  the  ocean)  ; 
(V)  land  waste  on  its  way  to  the  sea.    These  three  headings  are  to  be  further 
subdivided  as  follows : 

(a)  Land  forms  should  be  subdivided  first  as  to  structure  and  second  as 
to  stage  of  development  in  the  cycle  of  sculpture.  The  simplest  structures 
should  be  considered  first,  and  of  these  coastal  plains  may  well  lead  the 
list,  while  mountains  of  greatly  disordered  structure  come  near  its  close. 
Under  each  of  these  categories  young  forms,  that  is,  forms  in  an  early 
stage  of  the  cycle  of  sculpture,  should  be  treated  first ;  then  mature  forms  ; 
finally  old  forms.  Crustal  movements,  occurring  at  any  time,  interrupt  the 
previous  cycle  and  introduce  a  new  one. 

(£)  Although  rivers  and  valleys  have  been  briefly  considered  in  the 
introductory  account  of  the  lands  in  general,  and  although  they  have  been 
encountered  repeatedly  in  the  accounts  of  the  different  kinds  of  land  forms, 
a  special  subdivision  may  be  well  made  for  their  fuller  consideration.  Here 
rivers  and  their  valleys  form  the  leading  topic,  the  argument  by  which  the 
subject  is  entered ;  and  as  such  they  may  be  presented  in  much  greater 
detail  than  was  appropriate  when  they  were  only  secondary  topics,  as  under 
land  forms. 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        45 

(V)  The  forms  assumed  by  the  waste  of  the  land  on  the  way  to  the  sea 
merit  recognition  ;  they  are  fully  worthy  of  an  independent  place  in  the 
scheme  of  treatment  in  relatively  advanced  study,  although  for  more 
elementary  work  the  topics  of  this  subdivision  may  be  distributed  under 
others. 

3.  The    consequences   of   special    climatic    conditions,    dry    and    cold, 
deserve  treatment  apart  from  the  consequences  of  normal  climatic  con- 
ditions ;  here  deserts  and  glaciated  areas  may  be  placed.    Any  kind  of  a 
land  form  in  any  stage  of  sculpture  may  be  now,  or  may  have  been  recently, 
arid  or  glaciated  ;  hence  this  chapter  must  follow  those  which  discuss  the 
sculpture  of  land  forms  in  a  normal  climate. 

4.  The  shore-line  is  best  given  a  final  chapter  to  itself,  so  that  all  kinds 
of  land  forms  may  be  known  when  the  work  of  the  sea  upon  the  lands  is 
taken  up.    Shore-lines  should  be  classified  first  according  to  their  original 
outline  as  determined  by  the  kind  of  land  form  on  which  the  sea  came  to 
lie  when  the  present  relative  position  of  land  and  sea  was  assumed  ;  and 
second  according  to  the  advance  in  the  systematic  changes  that  are  pro- 
duced by  the  action  of  the  sea  on  the  original  outline. 

Principles  of  Systematic  Physiography.  There  are  several 
principles  of  importance  to  be  observed  in  the  treatment  of 
systematic  physiography. 

The  number  of  categories  into  which  physiographic  items 
are  divided  should  be,  as  has  already  been  suggested,  greatly 
increased  over  the  usual  limit,  and  the  categories  should  be 
treated  as  idealized  types  as  far  as  possible.  Each  category 
should  be  illustrated,  if  possible,  by  a  type  diagram,  on  which 
the  essential  features  are  clearly  presented,  and  from  which  the 
unessential  details  are  carefully  omitted.  Then,  in  order  to  con- 
nect the  ideal  with  the  actual,  good  examples  of  the  various 
types  should  be  instanced,  the  examples  being  selected  chiefly 
from  the  home  country,  but  without  undue  neglect  of  the  rest 
of  the  world. 

The  various  categories  of  the  subject  must  receive  explanation 
as  well  as  description,  because  of  the  great  aid  that  comes  to 
the  memory  through  the  understanding,  and  because  of  the 
higher  order  of  intelligence  that  is  developed  by  a  rational 
instead  of  an  empirical  consideration  of  things.  Explanation 
has  long  been  accorded  to  the  phenomena  of  the  atmosphere 
and  of  the  ocean ;  it  should  be  applied  with  equal  care  to  the 
forms  of  the  land.  For  this  purpose  it  is  necessary  to  accept 


46  EDUCATIONAL  ESSAYS 

in  a  more  whole-soi  led  manner  than  is  customary  among  geog- 
raphers the  processes  of  deformation  and  erosion  by  which  the 
lands  are  given  their  observed  forms.  It  does  not  suffice  to 
stop  at  small  illustrations,  such  as  sand  dunes  and  gorges  ;  the 
value  of  uplift  in  producing  coastal  plains,  of  deformation  in  pro- 
ducing block  mountains,  and  of  erosion  in  carving  the  uplifted 
forms,  must  be  more  fully  recognized.  It  is  chiefly  by  the 
adoption  of  this  principle  that  the  progress  of  recent  years  has 
been  made. 

It  should  be  observed  that,  with  the  explanatory  treatment, 
there  comes  a  good  share  of  deductive  consideration,  hitherto 
not  consciously  recognized  as  a  part  of  the  mental  equipment 
of  the  geographer  in  his  study  of  the  lands.  Although  inference 
and  deduction  have  been  abundantly  exercised  in  explaining 
the  winds  and  the  tides,  it  seems  to  have  been  thought  that 
deduction  had  no  place  in  the  treatment  of  land  forms.  It  may, 
however,  be  safely  affirmed  that,  as  a  matter  of  good  practice, 
deduction  enters  largely  into  any  serious  attempt  at  giving 
systematic  explanation  to  plains  and  plateaus,  mountains  and 
volcanoes,  rivers,  valleys,  and  shore-lines.  This  phase  of  physi- 
ographic study  deserves  careful  consideration  by  those  who  wish 
to  make  the  most  of  the  newer  methods. 

Every  category  of  physiographic  elements  should  be  accom- 
panied by  examples  of  the  responses  made  to  it  by  organic 
forms.  It  is  not  enough  to  take  up  the  organic  responses  after- 
ward ;  the  habit  must  be  formed  of  associating  these  responses 
with  the  study  of  the  environing  elements.  It  is  too  often  the 
case  that  physiographic  features  are  treated  independently,  as 
if  they  had  no  connection  withfrthe  organic  world,  even  when 
such  connection  may  be  easily  found.  Such  treatment  does 
little  toward  the  formation  of  the  habit  of  bringing  the  two 
halves  'of  geography  into  their  natural  relations.  The  usual 
treatment  of  the  earth  as  a  globe  under  the  title  of  mathematical 
geography  gives  good  illustration  of  unrelated  physiography.  It 
should  always  be  pointed  out,  in  studying  this  division  of  the 
subject,  that  the  wide  distribution  of  organic  species  is  an  im- 
mediate consequence  of  the  globular  form  of  the  earth ;  for 
only  a  globular  earth  can  have  its  surface  so  generally  level  as 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        47 

to  permit  organic  migration  over  large  arc?.3.  The  restraining 
effect  of  mountain  ranges  as  barriers  should  suffice  to  show  how 
greatly  the  facility  of  movement  from  place  to  place  over  most 
parts  of  the  earth  is  dependent  on  the  surface  of  the  globe 
being  not  far  from  level,  when  considered  as  a  whole.  Examples 
of  organic  consequences  thus  related  to  physiographic  controls 
are  the  very  life  of  the  subject. 

Finally,  the  various  categories  of  physiographic  elements 
should  be  arranged  according  to  a  reasonable  system.  The  ele- 
ments coexist  in  nature,  but  in  our  study  of  them  their  consid- 
eration must  be  linear,  one  after  the  other.  There  is  to-day  no 
generally  accepted  order  of  arrangement.  For  example,  the 
School  of  Geography  of  the  University  of  Oxford  offers  a  long 
vacation  course  for  the  summer  of  1902,  including  a  series  of 
lectures  on  "  Types  of  Land  Forms  and  their  Distribution," 
under  which  the  following  headings  are  announced:  "  Table- 
lands," "  Young  Folded  Mountains,"  "  Denudation  Highlands," 
"  Plains,"  and  "Coastal  Regions."  Again,  a  committee  of  the 
New  York  State  Science  Teachers'  Association  has  submitted 
a  report  in  which  shore-lines  follow  the  ocean  and  precede  the 
lands.  Evidently  discussion  is  needed  on  this  problem  of 
arrangement  in  order  to  bring  about  some  approach  to  a  con- 
sistent system.  Hence  even  so  subordinate  a  matter  as  that  of 
arrangement  calls  for  more  serious  consideration  by  mature 
students  than  it  has  yet  received. 

Regional  Physiography.  The  physiographic  description  of  a 
limited  region  cannot  be  profitably  undertaken  until  after  sys- 
tematic physiography  has  been  well  developed.  It  is  true  that 
the  whole  content  of  physiography  consists  of  items  gathered 
from  definite  localities,  and  that  the  parts  must  be  known  be- 
fore the  whole ;  but  it  is  equally  true  that  no  well-ordered 
account  of  any  region  can  be  given  until  the  facts  gathered 
from  many  parts  of  the  world  have  been  thoroughly  discussed 
and  systematized. 

The  regional  account  of  Minnesota,  for  example,  involves  the 
position  of  Minnesota  on  the  globe,  and  the  place  of  Minnesota 
with  respect  to  the  general  system  of  atmospheric  movements, 
and  thus  draws  something  from  the  first  and  second  divisions 


48  EDUCATIONAL  ESSAYS 

of  systematic  physiography,  as  above  stated.  It  involves  the 
existence  of  the  state  as  part  of  a  large  land  mass,  and  thus 
draws  something  from  the  general  features  of  the  large  land 
masses ;  and  with  this  goes  the  effect  of  a  central  continental 
position  on  climatic  conditions.  The  further  account  of  the  state 
involves  the  description  of  all  the  different  kinds  of  land  forms 
within  its  borders ;  if  these  items  are  to  be  presented  with  best 
effect,  they  must  follow  an  order  that  indicates  their  general 
relations,  and  this  draws  largely  from  the  systematic  study  of 
land  forms.  It  may  therefore  be  urged  that  the  mature  develop- 
ment of  systematic  physiography  will  do  much  to  advance  the 
mature  understanding  of  regional  physiography,  and  that  a 
student  who  has  carried  his  systematic  studies  as  far  as  the  con- 
dition of  the  science  allows,  will  make  excellent  progress  when 
he  turns  his  attention  to  the  study  of  a  limited  area.  There  are, 
however,  very  few  monographs  by  which  the  truth  of  this  con- 
tention can  be  supported  ;  there  are,  as  yet,  very  few  works  in 
which  the  physiography  of  a  region  has  been  maturely  studied 
in  view  of  a  well-developed  scheme  of  systematic  physiography. 
Relation  of  Systematic  and  Regional  Physiography.  The  older 
books  on  physical  geography  frequently  contained  chapters  on 
the  several  continents,  in  which  the  attempt  was  made  to  present 
the  actual  distribution  of  the  different  kinds  of  physical  features 
that  had  been  briefly  explained  on  earlier  pages.  The  tendency 
to-day  is  to  replace  the  pages  formerly  allowed  to  regional 
description  with  an  extension  of  the  pages  allotted  to  systematic 
description,  for  the  reason  that  no  sufficient  knowledge  of  the 
many  kinds  of  things  treated  in  physical  geography  can  be  gained 
if  the  actual  distribution  of  the  many  kinds  of  things  over  the 
world  is  attempted.  The  increased  attention  thus  given  to  sys- 
tematic study  is  certainly  an  advantage,  and  if  the  idealized 
types  of  systematic  study  are  illustrated  by  a  good  number  of 
actual  examples  from  many  parts  of  the  world,  the  student  will 
have  no  ground  of  complaint.  It  is  as  much  a  mistake  to  attempt 
regional  physical  geography  in  the  year  that  is  granted  to  this 
subject  in  the  high  school  as  it  would  be  to  teach  the  flora  or 
the  fauna  of  various  countries  in  the  year  that  is  allotted  to 
botany  or  zoology.  All  the  trend  of  the  newer  teaching  in  the 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        49 

biological  sciences  is  in  the  direction  of  a  more  appreciative 
knowledge  of  typical  forms,  studied  in  view  of  their  relations  to 
large  problems  of  growth,  classification,  and  evolution.  School 
study  of  the  distribution  of  plants  and  animals  is  in  danger  of 
deteriorating  to  a  mere  study  of  names,  and  the  same  is  true  of 
regional  physical  geography.  If  the  description  of  the  conti- 
nents is  attempted  in  the  year  that  is  given  to  physiography  in 
the  high  school,  the  time  given  to  systematic  physiography  must 
be  very  insufficient,  and  the  regional  description  must  therefore 
be  very  defective. 

There  are,  however,  certain  divisions  of  systematic  physiog- 
raphy in  which  what  seems  at  first  to  be  a  real  or  regional  study 
is  advisable ;  namely,  the  chapters  on  the  atmosphere  and  the 
ocean.  The  reason  for  this  may  be  easily  seen.  The  greater 
features  of  temperature  distribution,  atmospheric  circulation, 
rainfall,  and  climate  are  really  parts  of  a  physiographic  phenom- 
enon whose  dimensions  are  as  large  as  the  earth.  Like  the  earth 
itself,  the  atmospheric  shell  as  a  whole  must  be  considered  if 
we  wish  to  acquire  an  understanding  of  the  relations  of  its  parts. 
We  have  but  one  atmospheric  shell  with  which  to  deal,  and 
hence  the  study  of  its  parts,  such  as  the  trade-winds,  the  sub- 
tropical belts,  and  so  on,  becomes  specific  and  to  that  extent 
regional.  In  the  study  of  rivers,  on  the  other  hand,  there  are 
many  examples  to  illustrate  the  relations  of  the  various  parts, 
—  basins,  divides,  valleys,,  streams,  flood  plains,  deltas,  etc.,— 
and  here  the  treatment  necessarily  becomes  general,  with  allu- 
sion to  specific  examples  only  as  a  means  of  illustrating  general 
principles. 

The  atmosphere  is  not,  however,  treated  wholly  by  the  regional 
method  ;  for  like  the  parts  of  rivers  which  have  small  dimensions 
relative  to  the  earth  on  which  they  occur,  there  are  in  the  atmos- 
phere also  certain  smaller  phenomena  of  frequently  repeated 
occurrence  in  place  or  time.  These  are  always  given  a  general 
instead  of  a  regional  treatment,  and  specific  examples  from  par- 
ticular regions  are  cited  only  as  illustrations  of  the  categories 
under  which  they  fall.  Land  and  sea  breezes,  mountain  and 
valley  winds,  thunder-storms  and  tornadoes  are  examples  of  ihese 
smaller  phenomena  ;  no  text-book  attempts  to  describe  them  all. 


50  EDUCATIONAL   ESSAYS 

It  is  the  same  with  the  ocean.  As  a  continuous  and  remark- 
ably uniform  sheet  of  water,  the  actual  ocean  may  be  treated  as 
a  physiographic  unit.  Variety  in  composition,  temperature,  and 
movement  is  limited  for  the  most  part  to  its  surface  portion ; 
and  even  here  the  distribution  of  temperature  and  the  arrange- 
ment of  the  larger  currents  are  essentially  symmetrical  with 
respect  to  the  equator,  as  if  they  were  but  parts  of  a  large  ter- 
restrial phenomenon.  When  it  comes  to  minor  features  like 
local  currents,  mention  can  be  given  to  only  a  few  typical 
examples,  such  as  are  afforded  by  the  backset  eddies  between 
the  Gulf  Stream  and  the  Carolina  coast,  by  which  the  cuspate 
capes  of  that  interesting  shore-line  are  determined.  So  with 
the  tides ;  the  unity  of  this  terrestrial  phenomenon  and  its  rela- 
tion to  the  moon  and  sun  should  be  pointed  out  and  explained ; 
but  the  infinite  variety  of  tidal  details  along  the  ocean  shores 
can  be  taught  only  by  means  of  type  examples,  each  of  which 
is  chosen  to  illustrate  a  class  of  tidal  movements. 

Something  of  regional  treatment  may  be  given  to  the  first  sub- 
division of  the  chapter  on  the  lands,  for  the  larger  continental 
masses  are  so  few  that  they  naturally  take  our  attention  individ- 
ually, as  the  individual  planets  take  the  attention  of  astronomers. 
On  the  other  hand,  the  plan  of  continental  structure  and  relief 
is  so  intricate  that  it  is  not  yet  well  resolved  even  by  the  most 
advanced  students  ;  hence  systematic  physiography  cannot  dwell 
long  on  the  large  divisions  of  the  lands.  The  continents  are 
best  studied  under  regional  physiography. 

Systematic  Ontography.  We  may  bring  from  the  systematic 
study  of  physiography  the  conviction  that  a  carefully  arranged 
classification  is  worth  the  labor  that  its  preparation  has  cost. 
The  possession  of  a  scheme  of  classification  fosters  the  habit  of 
referring  newly  found  items  to  their  proper  place  among  their 
fellows.  Items  thus  properly  placed  become  much  more  valu- 
able as  elements  of  a  well-coordinated  series  than  when  arranged 
empirically,  as,  for  example,  in  the  order  of  acquisition.  Let  us, 
then,  take  up  ontography  with  the  intention  first  of  seeking  out 
all  manner  of  individual  examples  of  responses  made  by  organ- 
isms,to  their  environment,  and  then  of  arranging  the  examples 
in  a  logical  order  with  respect  to  certain  general  principles. 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        51 

Thus  arranged,  similar  items  are  soon  generalized  into  cate- 
gories, each  one  of  which  is  described  as  a  type,  rationally  ex- 
plained in  relation  to  the  factor  of  physical  environment  that  has 
produced  it,  and  illustrated  by  specific  examples.  There  can 
be  little  question  that  the  subject  will  grow  rapidly  if  it  is 
thus  cultivated. 

It  is  to  be  noted  that  the  classification  here  proposed  deals 
with  organic  responses  as  effects,  and  that  the  physiographic 
causes  therefore  enter  only  secondarily.  In  systematic  physiog- 
raphy it  was  the  causes  or  controls  that  were  classified,  and  the 
organic  effects  came  in  secondarily.  Thus  the  threads  of  physi- 
ography and  ontography  run  different  ways ;  they  are  the  warp 
and  the  woof  whose  close  interweaving  shows  us  the  plexus  of 
relationships  that  constitute  the  content  of  geography  proper. 
On  whichever  series  of  considerations  one  may  begin,  he  will 
be  led  over  the  whole  subject  if  he  follows  the  series  to  its  end. 

The  chief  writer  on  what  I  am  here  calling  ontography  is 
Ratzel,  who  has  given  an  elaborate  discussion  of  human  condi- 
tions in  relation  to  their  surroundings  in  his  "  Anthropogeo- 
graphie."  The  subject  deserves  an  even  more  general  and  more 
systematic  treatment  than  it  there  receives.  This  is  not  the 
place  to  set  forth  its  many  divisions,  but  I  may  be  permitted  to 
indicate  briefly  some  of  the  more  striking  ones. 

Every  organic  species  may  be  considered  as  possessing  certain 
structures,  as  carrying  on  certain  habitual  life  processes,  and  as 
occupying  certain  habitats.  Many  of  the  structures,  processes, 
and  habitats  are  responses  to  physiographic  causes  ;  as  such  they 
enter  into  the  content  of  ontography  and  indicate  its  three  chief 
divisions.  The  light  bones  and  feathers  of  flying  birds  are  a 
response  to  their  flight  through  the  unsustaining  air.  The  tor- 
pidity of  many  animals  during  winter  is  a  response  to  climatic 
conditions.  The  division  of  a  genus  into  several  similar  species 
on  the  different  islands  of  an  archipelago,  as  in  the  remarkable 
case  of  the  cassowaries,  is  the  response  to  the  production  of  the 
islands  by  the  partial  submergence  of  a  once  continuous  area. 
Numberless  instances  of  these  kinds  might  be  cited. 

Each  of  the  three  divisions  of  ontographic  responses  is  of 
two  kinds.  The  responses  of  one  kind  are  brought  down  as 


52 


EDUCATIONAL  ESSAYS 


inheritances  from  beginnings  in  an  earlier  time,  maintained  to-day 
because  their  physiographic  controls  are  persistent ;  these  are 
the  more  numerous  (except,  perhaps,  as  regards  habitat).  The 
responses  of  the  other  kind  are  of  recent  development,  and  are 
therefore  the  more  immediate  material  of  ontography.  Those  of 
the  first  kind  are,  however,  only  less  directly  pertinent  to  ontogra- 
phy, for  they  are  the  responses  to  the  paleographies  of  geological 
time,  and  can  be  cut  off  from  those  of  to-day  only  by  an  arbitrary 
separation. 

The  most  important  inherited  responses  are  those  determined 
by  long-  persistent  conditions  of  environment,  such  as  are  com- 
mon to  the  physiographies  of  all  ages.  The  habit  of  breathing 
oxygen,  for  example,  universal  among  plants  and  animals,  may 
be  reasonably  regarded  as  a  response  to  the  widespread  occur- 
rence of  this  gas,  uncombined,  but  active  in  entering  into  combi- 
nation with  organic  substances,  whether  it  is  dissolved  in  the 
ocean  or  free  in  the  atmosphere.  A  great  number  of  animals 
have  a  dorsal  and  a  ventral  portion,  and  an  arrangement  of 
skeleton  and  muscles  with  respect  to  the  vertical  line  of  gravita- 
tive  force.  This  is  evidently  the  result  of  living  on  an  earth 
whose  mass  greatly  exceeds  that  of  the  organism.  Escape  from 
responsibility  to  omnipresent  gravity  is  possible  only  for  those 
forms  whose  density  equals  that  of  the  medium  in  which  they 
live,  as  with  many  marine  animals,  or  whose  minuteness  makes 
them  the  play  of  every  passing  breeze,  as  with  innumerable 
microscopic  organisms. 

The  difference  of  coloring  of  the  ventral  and  dorsal  surfaces 
is  the  response  to  the  external  source  of  the  light  by  which  the 
earth's  surface  is  illuminated.  The  downward  growth  of  plant 
roots  and  the  upward  growth  of  stems  seem  to  be  responses  both 
to  light  and  to  gravity.  All  organs  of  sight,  voice,  and  hearing 
appear  to  be  responses  to  physical  properties  of  environing  media. 
The  development  of  these  organs  has  been  slow,  but,  once 
developed,  their  profit  has  been  so  great  that  they  have  been 
persistently  inherited  wherever  the  conditions  under  which  they 
were  developed  have  endured.  Sight  is  the  means  of  taking 
notice  of  the  bundle  of  strongest  solar  radiations  directly  inci- 
dent upon  or  reflected  to  the  organism  ;  it  is  given  up  after  being 


PROGRESS  OF  GEOGRAPHY  IN  THE   SCHOOLS        53 

once  acquired  only  by  cavern  animals  living  in  total  darkness. 
With  the  development  of  sight  on  the  part  of  pursuers,  there 
seems  to  have  come  the  device  of  invisibility  on  the  part  of  some 
of  the  pursued,  as  with  those  transparent  marine  organisms  that 
so  perfectly  imitate  the  invisibility  of  the  water  in  which  they 
float.  Hearing  is  the  device  for  taking  note  of  the  air  or  water 
waves  that  are  excited  by  some  neighboring  disturbance.  Voice 
is  rarer  than  hearing,  and  seems  to  be  especially  associated  with 
the  organs  for  air  breathing  in  the  higher  vertebrates. 

The  list  of  responses  of  this  kind,  stated  in  association  with 
their  causes,  would  be  very  long  before  it  was  complete.-  There 
is  to-day,  unhappily,  no  place  where  the  list  is  to  be  found  on 
record.  All  the  examples  of  responses  given  above  may  be  con- 
nected by  a  continuous  series  of  other  examples  with  the  most 
modern  and  commonplace  illustrations  of  geographical  relation- 
ships. It  is  only  under  the  most  arbitrary  ruling  that  the  imme- 
diate, simple,  and  manifest  responses  are  considered  pertinent 
to  geography,  while  the  remote,  complex,  and  obscure  responses 
are  referred  to  some  other  science  or  neglected.  The  resort  to 
talus  crevices  for  shelter  by  beasts,  and  to  caves  under  overhang- 
ing ledges  by  man ;  the  use  of  mud  by  wasps,  of  twigs  by  birds, 
of  wood,  stone,  or  ice  by  man  in  building  shelters  ;  the  housing  of 
colonies  of  bank-swallows  in  sand-banks  and  of  communities  of 
Chinese  in  loess  bluffs ;  the  settlement  of  beavers  on  water- 
courses, of  men  at  fords  and  harbor  heads ;  the  gathering  of  a 
manufacturing  population  about  the  water-power  of  modern 
Niagara,  —  all  these  are  examples  of  the  ontographical  habit 
that  organized  beings  have  of  taking  advantage  of  their  surround- 
ings. All  the  content  of  economic  or  commercial  geography, 
whose  modern  development  is  of  so  promising  an  interest,  is 
but  a  manifestation  of  a  special  phase  of  this  universal  habit.  It 
is  of  course  desirable  to  select  the  simple,  the'  manifest,  or  the 
"  important "  for  exposition  in  elementary  teaching,  but  the 
mature  geographer  can  be  satisfied  with  no  such  arbitrary 
bounds  for  his  study. 

The  location  of  roads  between  neighboring  villages  on  a  plain, 
of  highways  over  passes,  of  tunnels  through  mountains,  of 
ship  channels  in  harbors,  offer  many  examples  of  responses  to 


54  EDUCATIONAL  ESSAYS 

physiographic  controls.  The  course  of  the  paths  beaten  down  by 
wild  animals  in  the  jungle,  of  the  trails  worn  by  cattle  on  their  way 
to  the  rare  watering  places  of  arid  regions,  of  the  lanes  followed 
by  pillaging  ants,  offer  equally  good,  although  less  conspicuous, 
examples  of  the  same  kind.  The  fleetness,  the  endurance,  the 
venom  of  the  animals  of  arid  deserts  have  been  instanced  as 
striking  examples  of  responses  to  an  environment  where  the 
maintenance  of  life  is  difficult.  The  spirit  of  independence  char- 
acteristic of  the  Swiss  has  been  regarded  by  one  writer  as  the 
cause  of  the  maintenance  of  independent  organization  even  in 
very  small  village  communities  ;  but  it  has  lately  been  shown  by 
Lugeon  that  the  physiographic  conditions  inherent  in  valleys 
among  lofty  mountains  are  such  that  only  small  villages  can  be 
developed  ;  and  thus  interpreted  the  spirit  of  independence  must 
be  regarded  as  the  result  of  the  ontographic  subdivision  of  Swiss 
settlements  into  small  villages.  The  growth  and  distribution  of 
plants  of  different  kinds,  as  influenced  by  rocky  surfaces,  com- 
position of  soil,  depth  and  abundance  of  ground  water  —  prob- 
lems of  modern  ecology  —  are  all  of  as  strictly  a  geographical 
nature  as  is  the  distribution  of  human  populations,  and  all  may 
be  treated  systematically  or  regionally. 

Ontography  should.be  pursued  even  into  forms  of  language 
and  habits  of  thought.  It  is  well  known  that  mountaineers  have 
a  greater  number  of  terms  for  peaks,  ridges,  and  passes  than 
are  to  be  found  among  the  inhabitants  of  plains  ;  that  dwellers 
in  the  deserts  find  need  of  giving  different  names  to  various 
kinds  of  sand  dunes,  while  the  people  of  a  moister  climate  get 
along  very  well  with  only  one.  "  The  river  of  life"  and  "  the 
valley  of  the  shadow  of  death  "  are  figures  of  a  manifestly  geo- 
graphical origin,  while  "amount,"  "  insulate,"  and  "  isolate  "  in- 
volve somewhat  concealed  geographical  figures  ;  but  the  origin  of 
"rival,"  "derive,"  and  "arrive"  in  a  geographical  root  would 
be  hardly  noticed  by  any  one  but  a  philologist,  yet  these  words 
certainly  serve  to  show  the  importance  that  has  long  been  given 
to  the  shore-line  that  divides  land  and  water.  In  how  many  other 
ways  language  is  ontographic,  no  one  has  yet  learned.  Fewkes 
has  shown  how  largely  the  religious  ceremonial  of  certain  Indian 
tribes  of  the  arid  Southwest  is  based  on  climatic  conditions ; 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        55 

thunderclouds  and  lightning  flashes  are  conventionalized  in  re- 
ligious decoration.  We  are  perhaps  prepared  to  ascribe  the 
simple  religions  of  pagan  savages  in  greater  or  less  degree  to 
physiographic  sources  ;  but  it  seldom  occurs  to  us  that  the  posi- 
tion and  the  character  of  the  heaven  and  the  hell  that  are  so 
closely  bound  up  with  the  faith  of  many  a  Christian  are  of  an 
equally  physiographic  origin.  The  ontographic  half  of  geogra- 
phy will  have  abundant  material  when  it  is  taken  up  for  serious 
study  by  mature  students. 

The  content  and  treatment  of  courses  on  regional  ontography 
can  be  inferred  from  what  precedes ;  they  cannot  be  detailed 
here,  for  lack  of  space,  but  they  would  include  all  that  is  com- 
monly understood  by  political  and  commercial  (economic)  geogra- 
phy, along  with  a  greater  emphasis  on  the  relation  of  these 
effects  to  their  causes  than  is  commonly  allowed. 

Systematic  and  Regional  Geography.  Systematic  geography  is 
the  orderly  study  of  the  relations  between  all  the  categories  of 
physiography  and  ontography.  Regional  geography  is  the  orderly 
study  of  all  these  relations  that  are  manifested  in  a  limited  area. 
It  would  be  premature  to  attempt  now  to  state  the  order  in  which 
the  categories  of  geography,  thus  understood,  should  be  taken 
up.  That  is  a  matter  which  may  well  engage  the  attention  of 
mature  geographers  for  some  time  to  come  without  exhausting 
the  discussion  that  it  deserves.  My  object  in  devoting  a  para- 
graph to  the  heading  above  is  to  reiterate  the  necessity  of  carry- 
ing forward  mature  geographical  study  toward  the  goal  here 
indicated,  as  a  practical  means  of  improving  the  condition  of 
geography  in  the  schools.  The  elements  of  the  subject  most 
fit  for  presentation  in  the  schools  cannot  be  determined  until 
the  subject,  as  a  whole,  is  more  thoroughly  discussed  than  it  is 
to-day ;  and  the  presentation  of  the  elements  cannot  be  of  the 
best  while  the  teachers'  knowledge  of  the  subject  is  far  below 
the  capacity  of  their  years,  as  is  now  generally  the  case. 

Relation  of  Mature  Geography  to  School  Geography.  In  the 
foregoing  pages  I  have  considered  the  higher  reaches  of  geo- 
graphical study,  because  it  seems  to  me  otherwise  impossible  to 
make  wise  plans  for  the  lower  reaches ;  but  in  order  that  this 
paper  shall  not  be  concerned  too  largely  with  questions  that  may 


56  EDUCATIONAL  ESSAYS 

seem  almost  transcendental,  it  may  close  with  what  may  be 
popularly  called  a  few  "  practical  suggestions,"  though,  for  my 
own  part,  I  believe  that  all  the  suggestions  here  made  have  a 
practical  bearing  on  school-teaching. 

Better  Preparation  of  Teachers.  One  of  the  most  direct  results 
that  would  follow  from  the  more  general  pursuit  of  geography 
as  a  mature  study  would  be  the  improvement  in  the  preparation 
of  teachers.  This  is  an  improvement  that  is,  according  to  my 
experience,  sadly  needed.  The  acquaintance  that  I  have  made 
during  a  number  of  sessions  of  the  Harvard  summer  course  in 
geography  has  convinced  me  that  teachers  of  geography  are  by 
no  means  informed  up  to  their  capacity  even  concerning  the 
elementary  aspects  of  their  subject.  The  idea  that  most  bays 
are  merely  drowned  valleys  is  a  surprise  to  many  teachers ;  the 
idea  that  a  river  which  exhibits  the  "  normal "  sequence  of  parts 
usually  described  is  a  mature  river,  and  that  young  and  old 
rivers  must  normally  have  a  different  arrangement  of  parts,  is  a 
novelty  to  them.  The  widespread  distribution  of  species  and 
the  extended  development  of  commerce  have  seldom  been  con- 
sidered rationally  as  the  responses  to  the  opportunities  for 
movement  offered  by  a  globular  earth.  The  division  of  mankind 
into  races  has  been  usually  treated  empirically  instead  of  as 
primarily  a  response  to  the  continental  division  of  the  lands,  and 
secondarily  to  important  mountain  and  desert  barriers.  There 
is  no  lack  of  a  conscientious  desire  nor  of  a  capacity  to  learn ; 
but  the  conclusion  has  been  forced  upon  me  that  many  of  the 
teachers  whom  I  have  met  have  been  intellectually  half-starved 
in  their  previous  study  of  geography ;  and  yet  the  teachers  to 
whom  I  refer  may  fairly  be  considered  as  of  better  than  average 
quality,  for  the  very  reason  that  they  have  spent  their  summer 
vacations  in  trying  to  make  themselves  better  still.  It  is  not 
necessary  to  inquire  here  into  the  causes  of  their  deficient 
training,  but  the  remedy  of  the  deficiency  may  be  looked  for 
with  much  confidence  in  the  elevation  of  the  general' status  of 
geographical  study  that  would  accompany  its  habitual  treatment 
by  specialists  in  colleges  and  universities.  It  is  important  to 
emphasize  in  this  connection  the  need  of  a  broader  and  higher 
preparation  for  teachers,  so  that  they  may  know  a  good  deal 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        57 

more  than  they  have  to  teach,  and  thus  gain  the  easy  mind  that 
characterizes  the  proficient  expert.  The  recognition  of  geog- 
raphy by  colleges  and  universities  will,  I  believe,  do  more  than 
anything  else  to  realize  this  desirable  end.  The  individual 
teachers  who  may  read  this  paragraph  will  not  be  able  alone 
to  exert  much  pressure  toward  a  change  to  a  better  order  of 
things  in  this  respect ;  but  the  organized  body  of  teachers  and 
superintendents  that  constitutes  the  National  Educational  Asso- 
ciation can  do  much  in  this  direction  if  they  are  once  fully 
persuaded  of  the  need  of  doing  it. 

Better  Equipment  of  Geographical  Laboratories.  It  is  not  so 
very  long  ago  that  physical  and  chemical  laboratories  were 
unknown  even  in  the  best  secondary  schools.  The  rapid  develop- 
ment of  observational  and  experimental  teaching  in  these  sub- 
jects makes  me  hope  that  the  time  may  not  be  long  distant 
when  the  best  high  schools  will,  as  a  matter  of  course,  be  pro- 
vided with  a  room  that  may  properly  be  called  a  geographical 
laboratory,  and  that  this  room  will  contain  a  good  working  col- 
lection of  material  for  the  observational  study  of  geographical 
problems.  Some  such  laboratories  already  exist.  As  strong  an 
organization  as  that  of  the  New  York  State  Science  Teachers' 
Association  has  favorably  considered  the  appointment  of  a  com- 
mittee to  prepare  a  report  upon  the  proper  equipment  of  a 
geographical  laboratory ;  and  a  collection  of  materials  for  geo- 
graphical teaching  has  lately  been  exhibited  in  Iowa.  All  this 
may  fairly  be  taken  as  a  hopeful  sign  of  the  times.  When  the 
grammar  schools  take  up  the  idea  of  practical  work  in  geography, 
the  matter  of  laboratory  equipment  will  become  of  so  large  com- 
mercial importance  that  publishers  will  enter  the  field ;  and  the 
walls,  racks,  and  tables  of  the  schoolroom  will  not  be  so  bare  as 
they  are  to-day.  But  it  is  evident  that  the  better  preparation  of 
teachers  must  precede  the  fuller  equipment  of  laboratories,  and 
that  the  teachers  must  first  become  familiar  in  their  own  train- 
ing with  the  use  of  abundant  laboratory  materials,  such  as 
should  be  found  in  institutions  of  higher  learning,  but  such  as  are 
to-day  too  generally  wanting  even  there.  Among  the  materials 
most  needed  are  wall  maps,  not  merely  of  climatic  elements,  of 
oceans,  and  of  continents,  but  of  typical  features  of  continents 


58  EDUCATIONAL  ESSAYS 

also ;  good  pictures  and  maps  of  the  actual  examples  by  which 
type  forms  are  illustrated,  models  of  land  forms,  lantern  slides 
in  large  variety,  well-selected  series  of  weather  maps,  plentiful 
large-scale  topographical  maps  such  as  are  published  by  our 
various  governmental  bureaus,  and  so  on.  Those  who  are  known 
to  have  gathered  together  a  laboratory  equipment  of  this  kind 
are  frequently  in  receipt  of  letters  from  superintendents  and 
teachers  asking  how  the  collection  may  be  duplicated ;  and  the 
letters  are  difficult  to  answer,  because  the  collections  have  been 
brought  together  piecemeal.  But  it  is  a  hopeful  sign  that  dealers 
in  lantern  slides  are  getting  out  catalogues  of  subjects  especially 
selected  for  the  illustration  of  physical  geography,  and  the  com- 
ing decade  will  undoubtedly  see  further  progress  in  this  line. 
Yet  here  again  it  will  only  be  a  repetition  of  the  experience  in 
physics  and  chemistry,  in  botany  and  zoology,  if  the  laboratory 
equipment  for  teaching  geography  in  schools  is  largely  developed 
in  the  more  fully  furnished  laboratories  of  our  colleges. 

Replacement  of  Items  by  Generalities.  The  hopeful  progress 
that  school  geography  has  made  in  the  last  twenty  years  is 
characterized  largely  by  a  diminution  in  the  number  of  isolated 
empirical  items  to  be  committed  to  memory,  and  by  a  corre- 
sponding increase  in  the  number  of  principles  and  generalizations 
to  be  intelligently  studied.  There  is  no  reason  for  thinking  that 
this  progress  has  reached  its  limit ;  there  is,  on  the  other  hand, 
much  ground  for  believing  that  as  the  teachers,  and  the  teachers 
of  teachers,  of  geography  gain  a  larger  and  broader  understand- 
ing of  the  subject  in  its  mature  development,  the  replacement 
of  the  lonesome  empirical  item  by  the  rational  category,  under 
which  the  items  are  grouped  in  good  fellowship,  will  continue 
to  increase  beyond  its  present  moderate  measure.  Items  must 
still  be  presented  in  abundance,  for  young  pupils  need  plenty 
of  specific  information ;  but  the  items  should  be  introduced 
in  illustration  of  the  categories  to  which  they  belong  rather 
than  as  sufficient  unto  themselves.  In  the  earlier  years  of 
school  study  the  items  ought  to  precede  the  category  and  the 
generalization,  for  first  progress  must  be  largely  inductive  ;  but 
by  the  time  that  the  high  school  is  reached,  and  probably  for  a 
year  or  two  sooner,  deduction  may  be  used  to  a  significant 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        59 

extent;  that  is,  the  generality  may  be  presented  first,  and  the 
items  may  then  follow  as  deductions  from  it  instead  of  preced- 
ing as  elements  of  its  induction.  Many  teachers  are  already 
using  the  deductive  method  in  teaching  the  distribution  of  wet 
and  dry  regions  as  determined  by  the  relation  of  mountain 
ranges  to  the  terrestrial  wind  system ;  and  the  success  of  the 
method  there  testifies  to  the  success  that  may  be  expected  in 
other  cases  where  the  mental  processes  involved  are  of  a  simple 
and  safe  order.  This  matter  deserves  more  emphasis  and  ampli- 
fication than  I  can  give  it  here  ;  suffice  it  to  say,  that  geography 
will  become  more  and  more  a  scientific  study  in  proportion  to 
the  use  that  is  made  of  the  fully  developed  scientific  method, 
which  always  involves  deduction  along  with  induction  in  treating 
problems  where  any  of  the  essential  facts  are  unseen. 

As  geography  becomes  rational,  the  purely  memoriter  method 
will  hold  lower  and  lower  rank  in  its  lessons.  Such  a  topic  as 
state  capitals,  learned  in  old-fashioned  days  as  a  monotonous 
recitation,  may  be  enlivened  by  an  enlarged  treatment  in  which 
many  other  facts  than  mere  name  are  associated  with  the  capital 
city.  Many  of  these  peripheral  facts  may  be  forgotten,  but  the 
central  fact  will  remain  more  firmly  fastened  in  the  memory  than 
if  it  had  but  one  empirical  attachment.  So  with  state  boundaries ; 
the  mere  recitation  of  boundaries,  apart  from  the  geographical 
relations  of  the  boundaries,  is  dull  work ;  dull  in  the  book,  dull 
in  the  teacher,  dulling  in  the  pupil.  Instead  of  having  such 
matters  learned  as  mere  feats  of  unreasoning,  unassociated 
memory,  they  should  always  be  combined  in  a  rational  way 
with  other  things,  so  as  to  make  for  intelligence  and  to  develop 
in  the  pupil  the  habit  of  looking  for  the  meaning  of  things 
instead  of  dulling  or  even  repressing  that  excellent  habit.  When 
rivers  are  taught  only  by  name  and  place,  it  must  be  that  little 
more  is  said  about  them  in  the  text-book  and  known  about  them 
by  the  teacher.  It  is  very  questionable  whether  it  is  worth 
while  to  use  any  share  of  school  hours  in  learning  so  slender  a 
geographical  item  as  the  mere  name  of  a  river.  It  would  be 
much  better  to  omit  altogether  the  account  of  a  country  that  is 
thus  treated  in  earlier  school  years,  and  to  take  it  up  for  the 
first  time  when  its  general  geography  is  treated  in  such  a  manner 


60  EDUCATIONAL   ESSAYS 

that  mountains,  climate,  rivers,  products,  and  cities  are  properly 
associated.  It  is  well  known  that  the  best  schools  are  making 
excellent  progress  in  such  lines  as  these ;  but  it  is  not  yet 
time  to  flatter  ourselves  that  pressure  toward  such  progress  is 
unnecessary. 

Geographical  Facts  must  be  made  more  Real.  I  recall  the  true 
story  of  a  little  girl  learning  her  lesson  in  a  question-and-answer 
geography.  Ques.  "Do  the  stars  shine  by  day  as  well  as  by 
night  ?  "  Ans.  "  They  do."  The  little  victim  was  seen  rocking 
herself  to  and  fro,  as  if  to  give  even  a  muscular  aid  to  her 
memory,  and  repeating,  "  They  do,  they  do,  they  do  —  they  do, 
they  do,  they  do."  The  theory  of  teaching  has  far  outgrown 
such  absurdities,  but  the  practice  has  not,  and  we  must  continue 
to  protest  against  them.  I  have  in  my  own  experience  seen 
members  of  a  class  of  teachers  try  to  answer  the  question, 
"  Why  are  the  days  longer  than  the  nights  in  summer?"  by 
recalling  the  words  from  some  printed  page  instead  of  by 
attempting  to  visualize  the  plain  facts  of  nature.  The  moral  of 
this  is  that  the  facts  of  geography  must  be  made  more  real  than 
they  can  be  by  studying  only  the  words  of  a  book.  All  sorts  of 
observational  devices  must  be  summoned  to  the  aid  of  the 
printed  page.  The  importance  of  this  principle  will  be  more 
fully  realized  when  it  is  recalled  that  children  can  know  much 
more  than  they  can  say ;  that  their  power  of  observation  is  far 
greater  than  that  of  expression ;  and  that  equality  of  these  two 
powers  is  not  always  reached  even  in  mature  minds.  In  order, 
therefore,  that  the  little  that  young  pupils  can  say  about  geog- 
raphy shall  be  properly  proportioned  to  their  whole  mental 
acquaintance  with  the  subject,  they  should  be  provided  with 
material,  especially  with  material  for  observation,  in  much  larger 
quantity  than  they  are  expected  to  recite,  and  in  much  more 
realistic  form  than  mere  names  and  definitions  of  unknown 
things. 

Yet  such  is  our  servitude  to  conventional  methods  that  we 
constantly  fail  to  teach  by  things ;  the  teaching  by  words  is  so 
much  easier.  Consider,  for  example,  the  rotation  of  the  earth. 
What  is  simpler  than  to  observe  in  an  effective  manner  the 
elementary  facts  upon  which  this  extraordinary  conclusion  is 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        6 1 

based  ?  and  yet  how  few  school  children  ever  learn  these  facts 
by  well-directed  observation  before  they  learn  the  verbal  state- 
ment of  the  conclusion  printed  in  a  text-book.  There  is  no 
inherent  difficulty  in  having  the  necessary  observations  made  by 
school  children  at  different  hours  during  a  two-session  school 
day,  —  particularly  that  most  significant  observation,  that  on 
the  second  day  the  sun  can  be  seen  to  approach  from  the  eastern 
side  of  the  sky  the  position  that  it  had  in  the  sky  twenty-four 
hours  before.  Again,  with  latitude,  in  how  many  schools  of  our 
country  are  the  necessary  facts  taught  by  observation  before 
terms  are  introduced  and  definitions  are  memorized  ?  Yet  here 
induction  is  surely  the  safe  and  sound  method.  I  am  con- 
vinced that  the  vagueness  of  popular  understanding  about  things 
of  this  kind  comes  from  an  over-emphasis  of  verbal  definitions 
in  school  years,  while  facts  easily  observed  are  under-emphasized. 
It  would  be  well  to  replace  the  names,  diameters,  and  distances 
of  the  planets  —  matters  of  small  geographical  import  in  any 
case  —  with  the  observational  proof  that  there  are  planets  or 
other  earths  to  be  seen  in  the  sky,  and  that  young  observers 
can  easily  follow  them  among  the  stars.  All  these  errors  of 
method  would  be  reduced  or  excluded  if  the  teacher  were  per- 
fectly easy-minded  on  such  problems ;  and  the  easy  mind  is 
best  gained  through  practical  acquaintance  with  observational 
methods  such  as  should  characterize  the  more  mature  stages 
of  geographical  study. 

Geography  indoors  should  be  as  largely  as  possible  supple- 
mented by  outdoor  observations  by  the  pupils  ;  yet  I  have  found 
a  great  diffidence  among  teachers  as  to  outdoor  observation, 
even  on  their  own  part.  They  may  have  learned  very  well 
indeed  everything  that  a  book  has  to  say  about  the  origin  of 
valleys,  they  may  profess  belief  in  the  destructive  work  of  the 
streams  that  flow  through  the  valleys,  yet  when  it  comes  to 
taking  a  class  of  children  outdoors  and  using  the  examples  of 
geographical  forms  such  as  the  neighborhood  affords,  there  is 
too  often  an  undue  hesitation.  The  teacher's  lack  of  self-confi- 
dence would  be  greatly  diminished  if  her  own  school  work  had 
been  more  liberally  guided,  and  if  her  days  of  professional 
preparation  had  been  spent  in  the  consideration  of  a  decidedly 


62  EDUCATIONAL  ESSAYS 

more  mature  phase  of  geography  than  that  on  which  her  skill 
is  afterward  to  be  exercised. 

Laboratory  Exercises  must  be  Specific.  With  an  increasing 
realization  of  geographical  facts  will  come  an  increasing  accuracy 
and  definiteness  of  knowledge  about  them  ;  and  this  will  be  a 
great  advance,  for  at  present  geographical  ideas  are  apt  to  be 
hazy.  My  recent  experience  with  Harvard  admission  examina- 
tions in  physiography  leads  me  to  fear  that  pupils  in  secondary 
schools  do  not  look  upon  this  division  of  geography  as  capable 
of  clear  statement,  such  as  they  know  is  expected  in  Latin  and 
geometry.  The  answers  to  such  a  question  as,  "  Describe  and 
show  by  diagrams  the  development  of  a  valley  and  its  flood 
plain  from  a  young  to  a  mature  stage,"  indicate  too  often  a 
vagueness  of  understanding  that  is  extremely  disappointing,  the 
more  so  in  that  it  reflects  imperfect  methods  of  teaching  as  well 
as  of  learning.  The  correction  of  this  difficulty  is  not  to  be 
secured  by  insisting  on  precise  verbal  recitations  from  the  text- 
book any  more  than  similar  difficulties  in  geometry  would  be 
overcome  by  insisting  on  verbatim  recitation  of  theorems.  The 
needed  reform  will  be  found  in  realistic  exercises  in  geography 
corresponding  to  blackboard  demonstrations  and  graphic  con- 
structions in  geometry.  But  it  is  essential  that  the  realistic 
exercises  in  the  geographical  laboratory  should  be  carefully 
planned,  in  order  that  they  should  be  closely  pertinent  to  and 
illustrative  of  the  text,  and  that  they  should  call  for  accurate 
thinking  and  performance  on  the  part  of  the  pupil.  The  elabo- 
ration of  a  series  of  fifty  or  more  such  exercises  in  physiography 
is  greatly  needed ;  and  those  who  have  experience  in  work  of 
this  kind  should  be  encouraged  to  give  specific  account  of  their 
methods  in  some  of  our  educational  journals,  or,  better  yet,  to 
prepare  laboratory  manuals  in  which  explicit  directions  shall  be 
given  as  to  outfit  and  process.  Among  the  simplest  and  at  the 
same  time  most  valuable  exercises  of  this  kind  for  the  chapters 
on  land  forms,  mention  may  be  made  of  the  drawing  of  outline 
maps  from  block  diagrams  of  typical  forms.  The  block  diagram 
being  an  oblique  bird's-eye  view,  and  the  map  being  seen  from 
directly  overhead,  there  is  just  enough  difference  between  the 
two  to  require  intelligence  in  changing  the  diagram  to  the  map, 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        63 

and  yet  not  to  demand  more  than  elementary  geographical  knowl- 
edge and  simple  manual  skill.  Maps  thus  prepared  should  always 
be  accompanied  by  a  descriptive  and  explanatory  text. 

Laboratory  exercises  should  not  be  limited  to  physiography ; 
they  should  be  devised  for  all  divisions  of  geography,  for  the 
devices  by  which  the  reality  of  geographical  items  and  the  truth 
of  geographical  principles  are  to  be  impressed  on  young  pupils 
cannot  be  compressed  into  a  text-book.  They  are  the  peculiar 
responsibility  of  the  teacher  and  the  laboratory.  Just  as  the 
breadth  of  opportunity  in  a  university  increases  with  the  abun- 
dance of  its  funds,  so  the  variety  of  devices  by  which  school 
children  are  aided  in  their  studies  will  increase  with  the  liber- 
ality of  a  teacher's  preparation.  One  of  the  most  promising  of 
all  methods  towards  escape  from  enslavement  to  verbal  texts  is 
the  cultivation  of  a  body  of  higher  learning  and  the  encourage- 
ment of  teachers  to  acquire  larger  and  larger  parts  of  it,  how- 
ever elementary  their  later  teaching  may  be. 

The  Rational  Element  and  the  Disciplinary  Value  of  Geogra- 
phy increase  Together.  It  is  very  likely  that  one  of  the  reasons 
for  the  general  omission  of  geography  from  the  list  of  college 
studies  is  that  it  does  not,  as  ordinarily  treated,  afford  sufficient 
intellectual  discipline  to  gain  a  place  among  other  subjects  whose 
value  in  this  respect  is  held  to  be  greater.  It  is  noticeable, 
however,  that  physical  geography  has  a  more  general  represen- 
tation in  colleges  than  any  other  branch  of  the  subject.  Hence 
it  may  be  expected  that  other  branches  will  gain  a  place  as  fast 
as  they  prove  themselves  worthy  of  it  by  showing  that  they  may 
be  as  disciplinary  and  profitable  as  physical  geography  is.  How- 
ever this  may  be,  there  can  be  no  question  that  the  disciplinary 
side  of  geography  deserves  more  emphasis  than  it  has  usually 
received  in  school-teaching.  The  remarks  made  above  as  to  the 
rank  of  the  "  tier  of  counties  "  question  are  pertinent  to  this 
paragraph  also.  There  is  every  reason  to  hope  that,  commensu- 
rate with  the  development  of  a  body  of  higher  learning  in  geog- 
raphy, there  will  be  an  increase  of  the  disciplinary  value  of  school 
geography.  Let  it  not  be  forgotten  that  good  progress  in  this 
direction  is  already  being  made.  The  intelligent  use  of  weather 
maps,  for  example,  is  a  case  in  point.  No  wide-awake  teacher 


64  EDUCATIONAL  ESSAYS 

of  physical  geography  to-day  can  be  content  without  using  a 
series  of  actual  weather  maps  in  illustration  of  weather  types ; 
the  exercises  that  may  be  based  on  these  maps  are  disciplinary 
in  a  high  degree.  The  records  shown  on  the  maps  may  be 
given  a  real  value  by  comparing  them  with  local  school  records. 
The  discussion  of  the  map  records  offers  admirable  training  in 
induction,  generalization,  and  deduction.  Exercises  may  be 
made  of  a  very  practical  kind,  training  the  hand  in  construction 
and  the  mind  in  expression.  The  knowledge  thus  gained  leaves 
little  room  for  credulity  in  a  subject  where  credulity  has  long 
flourished.  How  different  all  this  is  from  the  old-fashioned  em- 
pirical description  of  weather  changes  !  Studies  of  this  kind 
inculcate  a  really  scientific  method ;  they  make  for  intelligence  as 
against  mere  docility ;  they  aid  in  opening  a  broad  understanding 
of  the  processes  of  nature.  And  yet,  accessible  as  weather  maps 
are  to-day,  simple  as  are  the  methods  of  their  practical  disci- 
plinary use,  it  is  rarely  the  case  that  they  are  used  to  their  full 
value,  even  in  high  schools,  much  less  in  grammar  schools. 

Every  good  thing  that  may  be  said  about  weather  maps  may 
be  said  with  equal  value  about  studies  of  land  forms,  provided 
the  study  is  based  on  laboratory  material  as  appropriate  to  the 
needs  of  this  division  of  geography  as  weather  maps  are  to  the 
other.  But  while  weather  maps  are  very  generally  available, 
models  of  land  forms  are  relatively  rare  and  expensive.  The 
most  disciplinary  results  in  this  division  of  the  subject  must 
therefore  wait  until  models  are  made  and  used  in  greater  num- 
ber in  college  teaching,  until  the  teachers  of  teachers  become 
familiar  with  the  models  during  their  college  course,  until  the 
intending  teachers  of  geography  are  made  acquainted  with  a  good 
variety  of  typical  models  in  their  own  high-school  and  normal- 
school  course,  and  until  the  models  themselves  are  demanded  for 
the  future  geographical  laboratories  in  high  schools  and  grammar 
schools.  It  is  largely  for  the  National  Educational  Association 
to  say  whether  our  great-grandchildren  or  our  grandchildren  or 
our  children  shall  be  the  beneficiaries  of  such  improvements  as 
better  laboratory  equipment  will  aid  in  bringing  about. 

Certain  Parts  of  Geography  are  not  presented  in  Good  Seqttence. 
With  the  various  improvements  already  noted,  we  may  expect 


PROGRESS  OF  GEOGRAPHY  IN  THE   SCHOOLS        65 

to  see  a  better  sequence  established  in  the  order  of  introduc- 
tion of  certain  elements  of  geographical  study.  As  the  rational 
method  is  further  developed,  there  will  be  a  decrease  in  the 
number  of  things  that  are  arbitrarily  introduced  on  account  of 
their  asserted  importance,  even  though  they  must  be  given  an 
empirical  instead  of  an  explanatory  treatment.  It  may  be  going 
too  far  to  say  that  this  class  of  topics  will  ever  be  as  completely 
excluded  from  geography  as  it  is  from  such  purely  deductive 
studies  as  geometry  and  algebra,  where  no  one  pretends  to  intro- 
duce a  theorem  or  a  principle  before  it  can  be  logically  approached 
by  a  series  of  preparatory  steps ;  yet  it  should  be  noted  that  in 
subjects  such  as  physics  and  chemistry,  where  inductive  and 
deductive  methods  are  combined,  the  sequence  of  topics  is 
logical  —  hardly  less  logical  than  in  mathematics.  It  is  not  cus- 
tomary to  make  an  empirical  statement  concerning  entropy  in 
an  elementary  text-book  on  physics,  however  important  the 
principle  of  entropy  may  be  to  the  more  advanced  student. 
Again,  a  careful  selection  of  things  to  be  studied  is  noticeable 
in  the  modern  books  on  botany  and  zoology,  although  this  method 
involves  the  omission  of  all  mention  of  many  plants  and  animals 
that  were  formerly  included  in  more  comprehensive  texts  on 
natural  history  ;  this  is  because  a  real  knowledge  of  a  few  things 
that  may  be  studied  observationally  is  held  to  be  of  greater 
value  than  a  nominal  knowledge  of  a  greater  variety  of  things. 

Certain  divisions  of  geography  seem  to  be  in  need  of  a  critical 
examination  as  to  the  logical  sequence  of  their  parts.  There  are 
at  present  too  many  instances  in  which  the  introduction  of  a 
topic  seems  to  be  more  indicative  of  a  desire  on  the  part  of  the 
author  of  the  text-book  to  display  his  knowledge  than  of  a  judi- 
cious estimate  as  to  what  is  appropriate  to  the  pupils  who  are 
to  use  the  book.  The  treatment  of  the  tides  sometimes  offers 
illustration  of  this  difficulty.  It  is  as  if  the  author  felt  bound  to 
make  mention  of  certain  facts  or  theories  because  of  a  supposed 
public  or  scientific  demand  for  them,  even  though  they  may 
involve  principles  which  the  pupils  who  are  to  use  the  book  can- 
not be  expected  to  have  learned.  The  theory  of  the  general  cir- 
culation of  the  atmosphere  and  the  effect  of  the  earth's  rotation 
on  the  course  of  the  winds  afford  similar  instances  of  the 


66  EDUCATIONAL  ESSAYS 

attempted  introduction  of  relatively  advanced  explanations  into 
elementary  texts,  because  of  a  supposed  conventional  or  popular 
demand  for  them.  A  way  out  of  the  difficulty  in  these  cases 
may  be  found  by  touching  very  lightly  on  the  more  involved 
parts  of  the  explanation,  and  by  replacing  the  more  difficult 
parts  with  a  selection  from  the  abundant  matters  of  fact  which 
can  be  easily  apprehended,  and  which  go  far  toward  forming  a 
sound  basis  on  which  real  explanation  may  be  based  in  later 
years. 

The  flattening  of  the  earth  at  the  poles  is  given  an  exaggerated 
importance  by  being  included  in  the  first  account  of  the  globular 
form  of  the  earth.  The  explanation  of  the  seasons  is  often 
attempted  before  the  pupil  has  gained  any  inductive  basis  for 
the  capital  fact  of  the  earth's  annual  revolution  around  the  sun. 
Latitude  and  longitude  are  as  a  rule  introduced  too  early.  The 
methods  of  finding  latitude  that  are  sometimes  taught  include 
data  empirically  provided  by  the  teacher.  Rearrangement  is 
needed  in  all  such  cases  if  geography  is  to  become  largely 
disciplinary. 

Distribution  of  the  Divisions  of  Geography  in  Secondary 
Schools.  General  descriptive  geography,  which  constitutes  the 
body  of  the  subject  in  the  years  before  the  high  school,  need 
not  be  subdivided  according  to  the  scheme  of  classification  of 
the  divisions  of  geography  given  above.  It  makes  a  beginning 
in  all  of  the  divisions.  As  at  present  conducted,  good  progress 
toward  better  methods  is  everywhere  noticeable,  but  there  is 
still  room  for  a  greater  development  of  systematic,  explanatory, 
and  realistic  treatment,  as  has  been  indicated  on  the  preceding 
pages.  Change  in  the  order  of  parts  is  not  seriously  demanded  ; 
change  in  the  proportion  and  emphasis  of  parts  is  going  on  in 
a  wholesome  manner,  and  largely  in  the  direction  here  advocated. 
Among  the  results  of  these  changes  is  a  possible  saving  of  time 
by  the  omission  of  unnecessary  details,  so  as  to  permit  the 
introduction  of  elementary  systematic  physiography  in  the  last 
year  before  the  high  school.  There  are  many  reasons  for  this 
change,  which  I  have  elsewhere  set  forth  at  some  length  ;  but 
it  may  be  here  noted  that  the  change  would  have  the  beneficial 
result  of  presenting  some  of  the  outlines  of  physiography  to  a 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        67 

greatly  increased  number  of  school  children ;  and  if  the  subject 
really  has  the  educational  value  that  is  claimed  for  it,  this  would 
be  a  national  blessing. 

High-school  geography  should  be  of  two  kinds.  If  the  feed- 
ing lower  schools  do  not  provide  a  course  in  elementary  physi- 
ography, then  the  high  school  must  provide  it,  and  by  preference 
in  an  early  year.  If  no  special  course  on  regional  physiography, 
such  as  the  physiography  of  the  United  States  or  of  North 
America,  is  offered,  then  the  systematic  course  should  give  as 
many  specific  illustrations  of  its  categories  as  possible.  In  the 
necessary  absence  of  a  course  on  systematic  ontography  in  sec- 
ondary schools,  ontographic  responses  should  be  liberally  intro- 
duced in  connection  with  their  physiographic  controls.  If,  on 
the  other  hand,  the  high  school  is  served  by  lower  schools  in 
which  a  good  course  on  elementary  physiography  has  been  given 
by  well-trained  teachers  to  well-trained  pupils,  then  the  high 
school  has  manifestly  two  courses  to  offer.  Regional  physiog- 
raphy of  the  United  States  may  be  introduced  in  an  early  year 
so  as  to  precede  a  later  course  in  commercial  geography, 
in  advanced  systematic  physiography,  or  (should  the  subject 
approve  itself  when  tried  in  colleges)  in  systematic  ontography. 

The  early  regional  course  should  be  liberally  broadened  by 
including  mention  of  features  like  those  of  the  home  country, 
but  situated  elsewhere  in  the  world,  and  by  abundant  mention 
of  organic  responses  to  local  physiographic  features.  It  could 
thus  be  made  disciplinary  and  educative  in  a  high  degree.  The 
course  on  commercial  geography  is,  if  well  founded  on  earlier 
physiographic  courses  and  well  developed  in  view  of  systematic 
ontography,  destined  to  take  an  important  place  in  the  schools  ; 
but  it  must  carefully  avoid  the  danger  of  introducing  too  much 
empirical  detail. 

The  course  on  more  advanced  systematic  physiography  could, 
if  placed  in  a  late  high-school  year,  reach  a  stage  of  relatively 
rigorous  discipline,  for  the  inculcation  of  which  more  serious 
books,  as  well  as  better-prepared  teachers  and  better-equipped 
laboratories,  would  be  needed  than  are  to  be  found  to-day.  If 
these  suggestions  seem  visionary,  one  need  only  look  at  the 
extraordinary  progress  made  in  the  last  fifty  years  of  our  school 


68  EDUCATIONAL   ESSAYS 

history  to  count  upon  the  realization  of  all  these  schemes  in  the 
next  fifty.  It  goes  without  saying  that  the  courses  thus  insti- 
tuted should  be  so  well  taught  that  they  could  be  built  upon  by 
still  more  advanced  work  for  those  students  who  go  to  college. 

Educational  Value  of  Geography.  There  are  two  different 
standards  by  which  the  value  of  a  school  study  may  be  meas- 
ured. One  is  the  so-called  practical  standard  of  use  in  life  work  ; 
the  other  is  the  more  intellectual  standard  of  capacity  for  enjoy- 
ment. There  is  no  danger  that  this  practical  nation,  with  its 
marvelously  rapid  material  progress,  will  fail  to  give  due  promi- 
nence to  the  practical  side  of  school  studies  ;  there  is  some  dan- 
ger that  the  intellectual  side  may  in  a  measure  be  neglected, 
from  the  very  magnitude  of  our  material  prosperity. 

The  practical  side  of  geography  is  best  taught  in  a  well- 
developed  course  of  commercial  geography  placed  in  the  later 
years  of  the  high  school,  after  earlier  courses  on  general  geog- 
raphy in  the  grades,  and  a  course  on  elementary  physiography 
either  in  the  grades  or  in  an  early  high-school  year,  as  above 
suggested.  Here,  if  anywhere,  is  it  important  that  the  principles 
of  systematic  ontography,  developed  as  they  ought  to  be  by  col- 
legiate and  university  study,  should  find  application.  If  com- 
mercial geography  is  to  gain  the  place  it  deserves,  it  is  of  vital 
importance  that  it  should  be  rationally  taught  as  that  part  of 
regional  geography  in  which  man,  the  trader,  responds  so  mar- 
velously to  his  environing  conditions.  We  have  only  to  regret 
that  the  keen  practical  intelligence  by  which  the  successful 
American  of  to-day  has  so  greatly  magnified  the  share  taken  by 
our  country  in  the  commercial  geography  of  the  world,  finds  so 
many  analogies  in  the  habits  of  the  predatory  species  of  the 
lower  animals  and  in  the  behavior  of  the  robber  barons  of  feudal 
times.  This  suggests  that  commercial  geography  should  be  par- 
alleled by  a  good  course  in  ethics. 

The  intellectual  profit  of  geography  comes  from  the  enjoy- 
ment that  every  active  mind  finds  in  really  seeing  the  facts  of 
the  world  about  him.  The  great  pleasure  that  has  come  to 
thousands  of  us,  young  and  old,  in  recent  years  from  the 
observational  study  of  birds  demonstrates  the  capacity,  hitherto 
latent  in  that  respect,  of  the  average  person  for  a  high  measure 


PROGRESS  OF  GEOGRAPHY  IN  THE  SCHOOLS        69 

of  simple,  unpractical  intellectual  enjoyment.  A  corresponding 
pleasure  is  in  store  for  those  who  learn,  see,  and  appreciate  the 
abundant  facts  and  relationships  of  geography,  many  of  which 
must  enter  into  the  experience  of  every  life.  If  the  possibility 
of  making  a  happy  adjustment  of  one's  self  to  his  environment 
comes  with  the  fuller  appreciation  of  the  order  of  nature,  so 
much  the  better.  It  is  evident,  however,  that  the  enjoyment  of 
the  opportunities  of  mature  life  will  not  have  been  increased  for 
those  whose  school  geography  was  merely  a  study  of  words  in  a 
book,  or  of  names  on  a  map,  rather  than  of  the  meaningful  facts 
of  the  world.  Hence  the  intellectual  no  less  than  the  practical 
value  of  geography  will  depend  largely  on  the  excellence  with 
which  it  is  taught. 


Ill 

THE  PHYSICAL  GEOGRAPHY  OF  THE  LANDS 

The  most  important  principles  established  in  physical  geogra- 
phy during  the  nineteenth  century  are  that  the  description  of 
the  earth's  surface  features  must  be  accompanied  by  explanation, 
and  that  the  surface  features  must  be  correlated  with  their 
inhabitants.  During  the  establishment  of  these  evolutionary 
principles,  exploration  at  home  and  abroad  has  greatly  increased 
the  store  of  recorded  facts  ;  the  more  civilized  countries  have 
been  in  large  part  measured  and  mapped ;  the  coasts  of  the 
world  have  been  charted ;  the  less  civilized  continents  have 
been  penetrated  to  their  centers.  This  harvest  of  fact  has 
been  an  indispensable  stimulus  to  the  study  of  physical  geogra- 
phy ;  yet  it  cannot  be  doubted  that  the  spirit  which  has  given 
life  to  the  letter  of  the  subject  is  the  principle  of  evolution,  — 
inorganic  and  organic.  This  is  especially  true  of  the  geography 
of  the  lands. 

The  century  has  seen  the  measurement  of  higher  peaks  in  the 
Himalayas  than  had  been  previously  measured  in  the  Andes. 
The  Nile  has  been  traced  to  its  source  in  the  lakes  of  equatorial 
Africa,  verifying  the  traditions  of  the  ancients ;  and  the  Kongo 
has  been  found  to  cross  the  equator  twice  on  its  way  to  the  sea. 
Facts  without  number  have  been  added  to  the  previous  sum  of 
knowledge.  But,  at  the  same  time,  it  has  been  discovered  that 
the  valleys  of  mountain  ranges  are  the  work  of  erosion ;  that 
the  product  of  valley  erosion  is  often  seen  in  extensive  pied- 
mont fluviatile  plains ;  that  waterfalls  are  retrogressively  worn 
away  until  they  are  reduced  to  the  smooth  grade  of  a  maturely 
established  river ;  and  that  interior  basins  are  slowly  filling 
with  the  waste  that  is  washed  in  from  their  borders  to  their 
floors.  Here  are  explanatory  generalizations  involving,  yet 
going  far  beyond,  matter  of  direct  observation.  Such  generali- 
zations in  geography  correspond  to  the  recognition  in  astronomy 

70 


THE  PHYSICAL  GEOGRAPHY  OF  THE  LANDS         71 

that  planetary  movements  exemplify  the  law  of  gravitation  ;  they 
are  the  Newton  as  against  the  Kepler  of  the  subject. 

The  sufficient  justification  of  the  demand  that  has  now  arisen 
for  explanation  and  correlation  in  the  study  of  land  forms  is 
found  in  the  repeated  experience  that  until  an  explanatory 
description  of  a  region  can  be  given,  one  may  be  sure  that  some 
of  its  significant  elements  pass  unnoticed  ;  and  until  the  controls 
that  it  exerts  on  living  forms  are  studied,  one  may  be  confident 
that  its  geographical  value  is  but  half  measured.  A  sentence 
from  Guyot's  "  Earth  and  Man  "  may  here  be  taken  as  a  guide  : 
"  To  describe,  without  rising  to  the  causes,  or  descending  to  the 
consequences,  is  no  more  science  than  merely  and  simply  to 
relate  a  fact  of  which  one  has  been  a  witness."  There  could 
hardly  be  devised  a  more  concise  and  searching  test  of  good  work 
than  this  quotation  suggests.  The  causes,  in  so  far  as  the  physi- 
cal geography  of  the  lands  is  concerned,  have  been  learned 
chiefly  through  the  study  of  geology ;  yet  it  does  not  by  any 
means  follow  that  all  geologists  are  possessed  of  such  knowledge 
of  these  causes  as  will  constitute  them  geographers.  The  con- 
sequences have  been  learned  through  the  study  of  evolutionary 
biology  ;  yet  a  distinct  addition  to  the  usual  discipline  of  biology 
is  required  in  order  to  apprehend  its  geographical  correlations. 
The  limited  space  allowed  to  this  article  will  require  that  further 
consideration  of  the  consequences  be  excluded,  in  order  to  give 
due  consideration  to  the  causes. 

One  of  the  preparatory  steps  in  the  century's  advance  was 
taken  by  the  German  geographer,  Ritter,  who,  near  the  begin- 
ning of  the  century,  advocated  a  new  principle  that  may  be 
illustrated  by  the  change  in  the  definition  of  geography  from 
"  the  description  of  the  earth  and  its  inhabitants  "  to  "  the  study 
of  the  earth  in  relation  to  its  inhabitants";  but  advance  beyond 
this  beginning  was  for  a  long  time  obstructed  by  certain  ancient 
beliefs.  Theological  preconceptions  as  to  the  age  of  the  earth 
and  the  associated  geological  doctrine  of  catastrophism,  although 
attacked  by  the  rising  school  of  uniformitarianism,  were  then 
dominant.  They  gave  to  the  geographer  a  ready-made  earth, 
on  which  the  existing  processes  of  change  were  unimportant. 
Furthermore,  the  belief  in  the  separate  creation  of  every  organic 


72  EDUCATIONAL  ESSAYS 

species  led  to  the  doctrine  of  teleology,  which  maintained  the 
predetermined  fitness  of  the  earth  for  its  inhabitants,  and  of  its 
inhabitants  for  their  life  work.  All  this  had  to  be  outgrown  before 
geographers  could  understand  the  slow  development  of  land 
forms  and  the  progressive  adaptation  of  all  living  beings  to  their 
environments.  Yet  the  beginning  that  Ritter  made  was  of 
great  importance,  and  it  would  have  led  further  had  it  not  hap- 
pened that  for  many  decades  professors  of  geography  in  Europe 
brought  chiefly  a  historical  training  to  their  chairs,  to  the  almost 
entire  neglect  of  physical  geography.  In  the  last  thirty  years 
there  has  been  a  reaction  from  this  condition  in  Germany  and 
France,  but  Italy,  with  many  professors  of  geography  in  her 
universities,  still  for  the  most  part  follows  historical  methods. 

In  the  victory  of  the  uniformitarians  over  the  catastrophists 
began  the  fortunate  alliance  of  geography  with  geology.  Instead 
of  believing  in  cataclysmic  upheavals  and  in  overwhelming  floods, 
Playfair  and  other  exponents  of  the  Huttonian  school  taught 
that  mountains  were  slowly  upheaved  and  slowly  worn  down. 
The  simplicity  of  Playfair's  argument  finds  excellent  illustration 
in  the  often-quoted  passage  regarding  the  origin  of  valleys. 

Every  river  appears  to  consist  of  a  main  trunk,  fed  from  a  variety  of 
branches,  each  running  in  a  valley  proportioned  to  its  size,  and  all  of  them 
together  forming  a  system  of  vallies,  communicating  with  one  another,  and 
having  such  a  nice  adjustment  of  their  declivities  that  none  of  them  join 
the  principal  valley  either  on  too  high  or  too  low  a  level ;  a  circumstance 
which  would  be  infinitely  improbable  if  each  of  these  vallies  were  not  the 
work  of  the  stream  that  flows  in  it. 

Descriptions  of  valleys  should  always  recognize  the  share  that 
rivers  have  had  in  eroding  them,  or  else  the  "  nice  adjustment 
of  their  declivities  "  may  pass  unnoticed. 

It  should  be  noted,  however,  that  to  this  day  explanation  is 
not  always  allowed  an  undisputed  place  in  the  treatment  of  the 
lands,  however  fully  it  is  accepted  as  appropriate  to  the  presen- 
tation of  other  divisions  of  physical  geography.  But  the  manner 
in  which  explanation  is  extending  over  a  larger  and  larger  part 
of  the  subject  gives  assurance  that  .the  geographers  of  the  com- 
ing century  will  insist  upon  a  uniformly  rational  treatment  of 
all  divisions  of  their  science.  The  active  phenomena  of  the 


THE  PHYSICAL  GEOGRAPHY  OF  THE   LANDS         73 

earth's  surface  first  secured  explanation ;  it  has  long  been  con- 
sidered essential  to  explain  as  well  as  to  describe  such  phenom- 
ena as  the  winds  of  the  air  and  the  currents  of  the  ocean ; 
indeed,  this  is  now  so  habitual  that  many  geographers  who  may 
object  to  the  explanation  of  a  peculiar  kind  of  a  valley  as  a 
trespass  upon  geology  will  nevertheless  demand  an  explanation 
of  rainfall  and  tides,  although  these  truly  geographical  subjects 
are  manifestly  shared  with  physics  and  astronomy.  Land  forms 
of  very  elementary  character,  like  deltas,  or  of  rapid  production, 
like  volcanoes,  have  had  to  give  some  account  of  themselves  all 
through  the  century  ;  but  it  was  not  for  many  years  after  the 
announcement  of  Playfair's  law  that  the  erosion  of  valleys  by 
the  rivers  that  drain  them  came  to  be  regarded  as  a  subject  appro- 
priate to  a  geographical  treatise.  Only  in  the  later  years  of  the 
nineteenth  century  has  the  fuller  treatment  of  this  beautiful 
subject  been  attempted  ;  even  now  much  of  it  remains  to  be 
developed  in  the  twentieth  century. 

The  treatment  of  physical  geography  will  be  much  more  even, 
to  the  great  advantage  of  its  students,  when  explanatory  descrip- 
tion is  applied  to  all  its  parts.  The  alluvial  fans  at  the  base  of 
arid  mountains  should  be  accounted  for  as  well  as  the  dunes  of 
deserts.  The  fault  cliffs  of  broken  plateau  blocks  and  the 
weathered  cliffs  of  retreating  escarpments  deserve  to  be  con- 
sidered as  carefully  as  the  wave-cut  cliffs  of  coasts  ;  the  essen- 
tial differences  of  these  forms  are  reached  most  easily  through 
their  explanation.  The  varied  sculpturing  of  a  mountain  slope 
may,  in  time,  come  to  be  as  well  understood  as  is  now  the  erosion 
of  a  simple  valley  in  a  low  plain. 

One  of  the  most  notable  elements  of  the  century's  progress  is 
the  increasing  breadth  of  view  gained  as  explanatory  descrip- 
tions are  extended  further  and  further  over  the  geographical 
field.  At  first  explanation  was  given  to  various  individual  fea- 
tures, item  by  item ;  now  it  is  recognized  that  an  appropriate 
place  must  be  provided  for  all  kinds  of  land  forms  in  a  compre- 
hensive scheme  of  physiographic  classification.  Many  instances 
of  the  earlier  stage  might  be  given,  beginning  with  examples 
from  the  works  of  Humboldt,  the  acknowledged  leader  of  scien- 
tific explorers  in  the  opening  of  the  nineteenth  century.  His 


74  EDUCATIONAL   ESSAYS 

attempts,  more  or  less  completely  successful,  to  explain  the 
facts  that  he  observed,  as  well  as  to  correlate  life  with  environ- 
ment, may  be  traced  all  through  his  writings  ;  but  his  "  Cosmos  " 
(1845)  did  not  reach  a  careful  discussion  of  land  forms,  although 
it  entered  so  far  into  an  explanatory  treatment  as  to  consider 
the  formation  of  mountain  ranges. 

Innumerable  examples  of  isolated  facts  and  special  explana- 
tions, unrelated  to  a  comprehensive  scheme  of  physiographic 
classification,  might  be  taken  from  the  reports  of  exploring  ex- 
peditions and  of  geological  surveys ;  from  books  of  travel  and 
from  geographical  and  geological  journals  with  which  the  nine- 
teenth century  has  filled  so  many  library  shelves ;  but  lack  of 
space  will  prevent  mention  of  all  sources,  save  a  few  treatises 
in  which  the  accumulated  knowledge  of  their  time  is  summa- 
rized. Such  a  work  as  Mrs.  Somerville's  "  Physical  Geography  " 
(1848)  gives  in  the  early  pages  a  brief,  general  consideration  of 
land  forms,  and  then  enters  at  once  upon  the  areal  description 
of  the  continents ;  later  pages  present  a  short  outline  of  the 
features  of  rivers,  and  then  the  rivers  of  the  world  are  taken 
up.  This  is  as  if  a  text-book  of  botany  should  pass  rapidly  over 
the  structure  and  classification  of  plants,  and  devote  most  of  its 
pages  to  the  flora  of  different  regions.  Again,  Kloden's  com- 
pendious geography  includes  a  volume  on  "  Physical  Geography  " 
(3d  ed.,  1873),  in  which  much  material  is  gathered;  but  the 
treatment  is  very  uneven,  as  is  natural  in  the  absence  of  a  good 
scheme  of  classification.  Glaciers  receive  much  attention,  but  val- 
leys are  rather  curtly  dismissed  ;  deltas  are  elaborately  described, 
but  little  space  is  given  to  other  forms  assumed  by  the  waste  of 
the  land  on  the  way  to  the  sea.  Ansted's  "  Physical  Geography  " 
(5th  ed.,  1871)  contains  an  abundance  of  facts,  but  many  of  them 
are  of  a  kind  which  could  better  be  presented  on  a  map  than  in 
verbal  form.  Many  pages  are  devoted  to  statistical  statements, 
from  which  no  student  can  gain  inspiration  for  further  study. 

A  decided  advance  over  earlier  books  in  the  way  of  rational 
or  explanatory  treatment  is  found  in  the  works  of  Peschel  and 
Reclus  ;  it  is  to  the  former  that  a  reaction  against  the  historical 
treatment  of  geography  in  Germany  is  largely  due,  while  the 
latter  is  to  be  credited  with  an  enlarged  attention  to  the  detail 


THE  PHYSICAL  GEOGRAPHY  OF  THE   LANDS         75 

of  land  forms ;  but  the  books  of  neither  of  these  authors  recog- 
nize the  systematic  evolution  of  land  forms.  The  same  may 
be  said  of  various  other  treatises  which  approach,  but  do  not 
yet  reach,  the  ideal  that  seems  to  be  in  sight.  One  of  the 
chief  responsibilities  of  the  geographer  —  the  description  of 
landscape  —  cannot  be  fully  met  by  students  who  accept  the 
principles  set  forth  in  these  books  as  their  guides ;  for,  in  spite 
of  the  increasing  attention  given  to  the  lands  in  modern  books, 
and  in  spite  of  the  greater  number  of  forms  recognized,  the 
combination  of  all  forms  in  a  well-organized  whole  is  not  yet 
accomplished. 

It  seems  to  have  been  against  the  empirical  method  of  such 
books  as  Ansted's  that  Huxley  protested  in  the  preface  to  his 
"  Physiography  "  (1878),  urging  its  replacement  by  a  more  edu- 
cative method.  He  wrote  : 

I  do  not  think  that  a  description  of  the  earth,  which  commences  by 
telling  a  child  that  it  is  an  oblate  spheroid,  moving  around  the  sun  in  an 
elliptical  orbit,  and  ends  without  giving  him  the  slightest  hint  towards  an 
understanding  of  the  ordnance  map  of  his  own  country,  or  any  suggestion 
as  to  the  meaning  of  the  phenomena  offered  by  the  brook  which  runs 
through  his  village,  or  of  the  gravel  pit  whence  the  roads  are  mended,  is 
calculated  either  to  interest  or  to  instruct.  .  .  .  Physiography  has  very 
little  to  do  with  this  sort  of  Physical  Geography.  My  hearers  were  not 
troubled  with  much  about  latitudes  and  longitudes,  the  heights  of  moun- 
tains, depths  of  seas,  or  the  geographical  distribution  of  kangaroos  or 
Composite.  ...  I  endeavored  to  give  them  ...  a  view  of  the  "place  in 
nature  "  of  a  particular  district  of  England  —  the  basin  of  the  Thames  — 
and  to  leave  upon  their  minds  the  impression  that  the  muddy  waters  of  our 
metropolitan  river,  the  hills  between  which  it  flows,  the  breezes  which 
blow  over  it,  are  not  isolated  phenomena,  to  be  taken  as  understood  because 
they  are  familiar.  On  the  contrary,  I  endeavored  to  show  that  the  applica- 
tion of  the  plainest  and  simplest  processes  of  reasoning  to  any  one  of  these 
phenomena  suffices  to  show,  lying  behind  it,  a  cause,  which  again  suggests 
another,  until,  step  by  step,  the  conviction  dawns  upon  the  learner  that  to 
attain  to  even  an  elementary  conception  of  what  goes  on  in  his  own  parish, 
he  must  know  something  about  the  universe  ;  that  the  pebble  he  kicks 
aside  would  not  be  what  it  is  and  where  it  is  unless  a  particular  chapter 
of  the  earth's  history,  finished  untold  ages  ago,  had  been  exactly  what  it 
was.  .  .  .  Many  highly  valuable  compendia  of  Physical  Geography,  for 
the  use  of  scientific  students  of  that  subject,  are  extant ;  but  in  my  judg- 
ment most  of  the  elementary  works  I  have  seen  begin  at  the  wrong  end, 
and  too  often  terminate  in  an  omnium- gatherum  of  scraps  of  all  sorts  of 


76  EDUCATIONAL  ESSAYS 

undigested  and  unconnected  information,  thereby  entirely  destroying  the 
educational  value  of  that  study  which  Kant  justly  termed  the  "  propaedeutic 
of  natural  knowledge." 

Here  we  find  clear  recognition  of  the  need  of  introducing  a 
consideration  of  causes,  just  as  was  urged  by  Guyot ;  and 
furthermore  a  recognition  of  the  need  of  linking  together  in 
their  natural  relations  all  the  items  which  constitute  the  content 
of  the  subject.  It  may,  however,  be  contended  that  the  attempt 
to  combine  in  a  single  course  of  study  the  elementary  princi- 
ples of  chemistry  and  physics,  of  geology  and  astronomy,  along 
with  those  of  physical  geography  is  not  practicable  from  an 
educational  point  of  view;  such  a  combination  will  not  secure 
either  the  clear  knowledge  or  the  strong  discipline  that  can  be 
derived  from  systematic  courses  in  two  or  three  of  these  sub- 
jects, presented  separately.  Text-books  like  Hinman's  "Eclectic 
Physical  Geography"  and  Mill's  " Realm  of  Nature,"  in  both 
of  which  a  broad  range  of  other  than  geographical  subjects 
is  covered,  do  not  seem  to-day  to  be  in  so  much  favor  as  those 
books  which  attend  more  closely  to  the  true  content  of  our 
subject.  Indeed,  with  respect  to  physical  geography,  consid- 
ered from  the  scientific  and  educational  point  of  view,  a  report 
on  College  Entrance  Requirements,  published  by  our  National 
Educational  Association,  presents  the  best  definition  and  outline 
of  the  subject  that  has  yet  appeared.  It  advises  the  omission  of 
irrelevant  matter,  however  interesting  such  matter  may  be  in 
itself.  The  principles  of  physics  and  the  succession  of  geolog- 
ical formations  with  their  fossils,  the  classification  and  distribu- 
tion of  plants  and  animals,  must  be  taught  elsewhere  ;  but  much 
profit  may  be  had  from  terrestrial  phenomena  by  which  the 
principles  of  physics  are  illustrated,  and  from  the  consequences 
of  past  geological  changes  in  determining  present  geographical 
conditions,  and  especially  from  the  physiographic  controls  by 
which  the  distribution  of  organic  forms  is  determined. 

The  general  scheme  under  which  all  land  forms  may  receive 
explanatory  description  must  consider  chiefly  the  movement  and 
erosion  of  the  earth's  crust.  Deformation  offers  a  part  of  the 
earth's  crust  to  be  worked  upon.  Various  destructive  processes 
of  erosion  work  upon  the  offered  mass,  and  the  streams,  with 


THE  PHYSICAL  GEOGRAPHY  OF  THE   LANDS         77 

their  transported  waste,  follow  the  depressions  carved  in  the 
surface.  So  important  is  the  element  of  erosion,  and  so  leading 
is  the  part  played  by  rivers  in  erosive  work,  that  McGee  would 
gather  all  land  forms  under  a  classification  determined  by  their 
drainage  systems.  Others  have  preferred  a  classification  based, 
first,  on  peculiarities  of  structure  as  determined  by  accumulation 
and  deformation,  and,  secondly,  on  the  progress  of  erosion ; 
but  in  either  scheme  the  erosive  work  of  rivers  is  so  important 
that  a  sketch  of  the  progress  of  the  physical  geography  of  the 
lands  towards  a  systematic  classification  of  its  items  may  well 
follow  the  order  in  which  valleys  have  been  explained,  branching 
off,  as  occasion  may  require,  from  the  leading  theme  of  rivers 
that  flow  under  a  normal  humid  climate  to  special  conditions  of 
erosion  under  an  arid  or  a  frigid  climate.  The  progress  which 
has  made  the  physical  geography  of  the  lands  what  it  is  to-day 
is  more  the  work  of  geologists  than  of  geographers ;  and  the 
chief  reason  for  this  is  the  indifference  of  many  geographers  to 
the  physical  side  of  their  subject, — an  indifference  that  was 
undoubtedly  favored  by  the  cultivation  of  historical  geography 
in  continental  Europe,  and  by  the  acceptance  of  the  traveler  or 
explorer  as  a  full-fledged  geographer  in  Great  Britain.  In  the 
United  States  it  is  only  in  the  latter  part  of  the  century  that 
the  physical  geography  of  the  lands  has  gained  a  scientific  stand- 
ing, and  the  advantages  that  it  now  enjoys  are  geographical 
grafts  upon  a  geological  stock. 

The  emancipation  of  geology  from  the  doctrine  of  catastro- 
phism  was  a  necessary  step  before  progress  could  be  made 
towards  an  understanding  of  the  lands.  The  slow  movements 
of  elevation  and  depression  of  certain  coasts  in  historic  time 
were  of  great  importance  in  this  connection.  Studies  of  geo- 
logical structures  at  last  overcame  the  belief  in  the  sudden  and 
violent  upheaval  of  mountain  chains,  which,  under  the  able  and 
authoritative  advocacy  of  Elie  de  Beaumont,  held  a  place  even 
into  the  second  half  of  the  century.  But  even  when  it  came  to 
be  understood  that  mountains  and  plateaus  have  been  slowly 
upheaved,  it  still  remained  to  be  proved  that  the  valleys  and 
canons  by  which  they  are  drained  were  produced  by  erosion, 
and  not  by  fractures  and  unequal  movements  of  elevation. 


78  EDUCATIONAL  ESSAYS 

Advance  was  here  made  on  two  lines.  Along  one,  a  better 
understanding  was  gained  of  the  forms  producible  by  defor- 
mation alone ;  along  the  other,  sea  currents,  floods,  and  earth- 
quake waves,  to  which  the  earlier  observers  trusted  as  a  means 
of  modifying  the  forms  of  uplift,  were  gradually  replaced  by  the 
slow  action  of  weather  and  water.  Processes  of  deformation 
were  found  to  act  in  a  large  way,  producing  massive  forms  with- 
out detail  —  broad  plains  and  plateaus,  extensive  domes,  simple 
cliffs,  and  rolling  corrugations  ;  and  thus  it  was  learned  that  the 
varied  and  detailed  forms  of  lofty  mountain  ranges  and  dissected 
plateaus  must  be  ascribed  almost  entirely  to  the  processes  of 
erosion.  But  it  should  be  noted  that  in  exceptional  instances 
land  forms  initiated  by  deformation,  so  recently  as  to  have  suf- 
fered as  yet  only  insignificant  sculpture,  may  exhibit  much 
irregularity.  The  most  striking  example  of  this  kind,  an  exam- 
ple of  the  very  highest  value  in  the  systematic  study  of  land 
forms,  is  that  afforded  by  the  diversely  tilted  lava  blocks  of 
southern  Oregon,  as  described  by  Russell. 

Turning  now  to  the  second  line  of  advance,  it  is  noteworthy 
that  so  keen  an  observer  as  Lesley  insisted,  as  late  as  1856, 
that  the  peculiar  topographical  features  of  Pennsylvania,  which 
he  knew  and  described  so  well,  could  have  been  produced  only 
by  a  great  flood.  But  the  principles  of  the  uniformitarians  were 
constantly  gaining  ground  against  these  older  ideas  ;  and  after 
the  appearance  in  England  of  Scrope's  studies  in  central  France 
and  of  Greenwood's  polemic  little  work  on  "  Rain  and  Rivers" 
(1857),  victory  may  be  said  to  have  been  declared  for  the 
principles  long  before  announced  by  Hutton  and  Playfair,  which, 
since  then,  have  obtained  general  acceptance  and  application. 

Yet  even  the  most  ardent  uniformitarians  would,  in  the  middle 
of  the  century,  go  no  further  than  to  admit  that  rain  and  rivers 
could  roughen  a  region  by  carving  valleys  in  it ;  no  consideration 
was  then  given  to  the  possibility  that,  with  longer  and  longer 
time,  the  hills  must  be  more  and  more  consumed,  the  valleys 
must  grow  wider  and  wider  open,  until,  however  high  and  uneven 
the  initial  surface  may  have  been,  it  must  at  last  be  reduced  to 
a  lowland  of  small  relief.  The  surface  of  such  a  lowland  would 
truncate  the  underground  structures  indifferently ;  but  when 


THE   PHYSICAL  GEOGRAPHY  OF  THE   LANDS         79 

such  truncating  surfaces  were  noticed  (usually  now  at  consider- 
able altitudes  above  sea  level,  as  if  elevated  after  having  been 
planed,  and  therefore  more  or  less  consumed  by  the  erosion  of 
a  new  system  of  valleys),  they  were  called  plains  of  marine 
denudation  by  Ramsay  (1847),  or  plains  of  marine  abrasion  by 
Richthofen  (1882).  To-day  it  is  recognized  that  both  subaerial 
erosion  and  marine  abrasion  are  theoretically  competent  to  pro- 
duce lowlands  of  denudation ;  the  real  question  here  at  issue 
concerns  the  criteria  by  which  the  work  of  either  agency  can  be 
recognized  in  particular  instances.  In  the  middle  of  the  century 
not  only  every  plain  of  denudation  but  every  line  of  escarpments 
was  held  by  the  marinists  to  be  the  work  of  sea  waves ;  and  it 
was  not  till  after  a  sharp  debate  that  the  bluffs  of  the  chalk 
downs  which  inclose  the  Weald  of  southeastern  England  were 
accepted  as  the  product  of  ordinary  atmospheric  weathering, 
instead  of  as  the  work  of  the  sea.  Whitaker's  admirable  essay 
on  "  Subaerial  Denudation,"  which  may  be  regarded  as  having 
given  the  victory  in  this  discussion  to  the  subaerialists,  was 
considered  so  heterodox  that  it  was  not  acceptable  for  publica- 
tion in  the  Qtiarterly  Journal  of  the  Geological  Society  of  Lon- 
don, but  had  to  find  a  place  in  the  more  modest  Geological 
Magazine  (1867),  whose  pages  it  now  honors.  So  signal  indeed 
was  this  victory  that,  in  later  years,  the  destructive  work  of  the 
sea  has  been  not  infrequently  underrated  in  the  almost  exclusive 
attention  given  to  land  sculpture  by  subaerial  agencies.  Truly, 
the  sea  does  not  erode  valleys ;  it  does  not  wear  out  narrow 
lowlands  of  irregular  form  between  inclosing  uplands,  as  was 
maintained  by  some  of  the  most  pronounced  marinists  in  the 
middle  of  the  century ;  but  it  certainly  does  attack  continental 
borders  in  a  most  vigorous  fashion,  and  many  are  the  littoral 
forms  that  must  be  ascribed  to  its  work,  as  may  be  learned 
from  Richthofen's  admirable  "  Fiihrer  f  iir  Forschungsreisende  " 
(1886).  As  this  problem  cannot  be  further  considered  here, 
the  reader  may  be  at  once  referred  to  the  most  general  discus- 
sion of  the  subject  that  has  yet  appeared,  in  an  essay  on  "  Shore- 
line Topography,"  prepared  by  Dr.  F.  P.  Gulliver  as  a  thesis  in 
his  graduate  work  at  Harvard  University  (1896),  and  published 
in  the  Proceedings  of  the  American  Academy  in  1899. 


80  EDUCATIONAL  ESSAYS 

At  about  the  time  when  the  sub-aerial  origin  of  valleys  and 
escarpments  was  being  established  in  England,  the  explorations 
and  surveys  of  our  western  territories  were  undertaken,  and  a 
flood  of  physiographic  light  came  from  them.  One  of  the  earli- 
est and  most  important  of  the  many  lessons  of  the  West  was 
that  Playf air's  law  obtained  even  in  the  case  of  the  Grand  canon 
of  the  Colorado,  which  was  visited  by  the  Ives  expedition  in 
1858.  Newberry,  the  geologist  of  the  expedition,  concluded 
that  both  the  deep  and  fissure-like  canon  and  the  broader  val- 
leys inclosed  by  cliff -like  walls  "  belong  to  a  vast  system  of  ero- 
sion, and  are  wholly  due  to  the  action  of  water."  Although  he 
bore  the  possibility  of  fractures  constantly  in  mind  and  examined 
the  structure  of  the  canons  with  all  possible  care,  he  "  every- 
where found  evidence  of  the  exclusive  action  of  water  in  their 
formation."  This  conclusion  has,  since  then,  been  amply  con- 
firmed by  Powell  and  Button,  although  these  later  observers 
might  attribute  a  significant  share  of  the  recession  of  cliffs  in 
arid  regions  to  wind  action.  In  a  later  decade  Heim  demon- 
strated that  the  valleys  of  the  Alps  were  not  explicable  as  the 
result  of  mountain  deformation,  and  that  they  found  explanation 
only  through  erosion.  By  such  studies  as  these,  of  which  many 
examples  could  be  given,  the  competence  of  rivers  to  carve 
even  the  deepest  valleys  has  been  fully  established ;  yet  so 
difficult  is  it  to  dislodge  old-fashioned  belief,  that  Sir  A.  Geikie 
felt  it  necessary  to  devote  two  chapters  in  his  admirable  "  Scen- 
ery of  Scotland  "  (1887)  to  prove  that  the  bens  of  the  Highlands 
were  not  so  many  individual  upheavals,  but  that  the  glens  were 
so  many  separate  valleys  of  erosion ;  and  as  able  an  observer  as 
Prestwich,  a  warm  advocate  of  the  erosion  of  ordinary  valleys 
by  their  rivers,  maintained  (1886),  with  the  results  of  our  west- 
ern surveys  before  him,  that  fissures  were  probably  responsible 
for  the  origin  of  the  deep  and  narrow  canons  of  the  Colorado 
plateau. 

The  tumultuous  forms  of  lofty  mountains,  "  tossed  up"  as 
they  seem  to  be  when  viewed  from  some  commanding  height, 
are,  in  by  far  the  greater  number  of  examples  yet  studied,  un- 
doubtedly the  result  of  the  slow  erosion  of  the  valleys  between 
them  ;  but  it  should  not  be  forgotten  that  regions  of  very  recent 


THE  PHYSICAL  GEOGRAPHY  OF  THE  LANDS         8 1 

disturbances  —  as  the  earth  counts  time  —  may  possess  strong 
inequalities  directly  due  to  deformation.  The  tilted  lava  blocks 
of  Oregon  have  already  been  mentioned.  The  bold  forms  of  the 
St.  Elias  Alps,  also  described  by  Russell,  are  regarded  by  him 
as  chiefly  produced  by  the  tilting  of  huge  crustal  blocks  on 
which  erosion  has  as  yet  done  relatively  little  work.  An  alto- 
gether exceptional  case  is  described  by  Button,  who  says  that 
on  the  margin  of  one  of  the  "  high  plateaus  of  Utah  a  huge 
block  seems  to  have  cracked  off  and  rolled  over,  the  beds 
opening  with  a  V  and  forming  a  valley  of  grand  dimensions." 
"  Rift  valleys,"  or  trough-like  depressions  produced  by  the 
down-faulting  of  long,  narrow,  crustal  blocks  with  respect  to 
the  bordering  masses,  are  occasionally  found,  as  in  eastern 
Africa,  where  the  "Great  Rift  valley"  has  been  described  by 
Gregory.  Trough-like  depressions  of  similar  origin,  but  much 
more  affected  by  the  degradation  of  their  borders  and  the  aggra- 
dation of  their  floors,  are  known  to  European  geographers  in 
the  valleys  of  the  Saone  and  of  the  middle  Rhine.  But  no  rift 
valley,  no  depression  between  the  tilted  lava  blocks,  resembles 
the  branching  valleys  that  are  produced  by  the  erosive  action  of 
running  water. 

Thus  far,  while  much  attention  had  been  given  to  the  work 
of  rivers,  little  or  no  attention  had  been  given  to  the  arrange- 
ment of  their  courses.  It  seems  to  have  been  tacitly  assumed 
that  the  courses  of  all  streams  were  consequent  upon  the  slope 
of  the  initial  land  surface.  The  explicit  recognition  of  this  ori- 
gin, indicated  by  the  provision  of  a  special  name  "  consequent 
streams,"  was  an  important  step  in  advance  due  to  our  western 
geologists.  The  discovery  soon  followed  that  rivers  have  held 
their  courses  through  mountain  ridges  that  slowly  rose  across 
their  path ;  the  rivers,  concentrating  the  drainage  of  a  large 
headwater  region  upon  a  narrow  line,  cut  down  their  channels 
as  the  land  was  raised.  This  idea  first  came  into  prominence 
through  Powell's  report  on  the  Colorado  River  of  the  West 
(1875),  in  which  he  gave  the  name  "  antecedent "  to  rivers  of 
this  class.  He  believed  that  the  Green  river,  in  its  passage 
through  the  Uinta  mountains,  was  to  be  explained  as  an  ante- 
cedent stream.  Much  doubt  has,  however,  been  thrown  upon 


82  EDUCATIONAL  ESSAYS 

this  interpretation.  Other  accounts  of  antecedent  rivers  have 
been  published,  and  to-day  the  Green  is  not  so  good  a  type  of 
antecedence  as  the  Rhine  below  Bingen,  the  Meuse  in  the 
Ardennes,  or  several  of  the  Himalayan  rivers  in  the  gorges 
that  they  have  cut  through  the  youngest  marginal  ridges  of  the 
range. 

Rapidly  following  the  establishment  of  these  two  important 
classes  of  valleys  came  the  recognition  of  the  very  antithesis  of 
antecedent  rivers  in  those  streams  which  have  grown  by  head- 
ward  erosion  along  belts  of  weak  structure,  without  relation  to 
the  initial  trough  lines.  To  these  the  term  "  subsequent "  has 
been  applied.  It  is  frequently  in  association  with  streams  of 
this  class  that  drainage  areas  are  rearranged  by  the  migration 
of  divides,  and  that  the  upper  waters  of  one  river  are  captured 
by  the  headward  growth  of  another.  This  is  accomplished  by 
a  most  beautiful  process  of  inorganic  natural  selection,  which 
leads  to  a  survival  of  the  fittest  and  thus  brings  about  a  most 
intimate  adjustment  of  form  to  structure,  whereby  the  more 
resistant  rock  masses  come  to  constitute  the  divides,  and  the 
less  resistant  are  chosen  for  the  excavation  of  valleys.  Many 
workers  have  contributed  to  the  solution  of  problems  of  this 
class,  notably  Heim,  in  his  studies  of  the  northern  Alps  (1876), 
and  Lowl,  who  showed  that  in  folded  mountain  structures  of 
great  age  the  original  courses  of  streams  might  be  greatly  altered 
through  the  development  of  new  lines  of  drainage  (1882).  A 
valuable  summary  of  this  subject  is  given  by  Philippson  in 
his  "  Studien  iiber  Wasserscheiden  "  (1886).  The  extraordinary 
depredations  committed  by  the  waxing  Severn  on  the  waning 
Thames  have  recently  been  set  forth  by  Buckman.  The  trim- 
ming of  side  branches  from  the  slender  trunk  of  the  Meuse  has 
been  recognized  in  France.  Many  remarkable  instances  of 
stream  captures  have  been  found  in  the  Appalachians,  where 
the  opportunity  for  the  adjustment  of  streams  to  structures  has 
been  exceptionally  good.  Hayes  and  Campbell  have,  on  the 
other  hand,  emphasized  the  importance  of  drainage  modifications 
independent  of  the  growth  of  subsequent  streams  on  weak  struc- 
tures, but  governed  by  a  slight  tilting  of  the  region,  whereby 
some  streams  are  accelerated  and  their  opponents  are  retarded. 


THE  PHYSICAL  GEOGRAPHY  OF  THE   LANDS         83 

It  should  be  noted  that  the  proof  of  the  adjustment  or  rearrange- 
ment of  drainage  marks  a  victory  for  the  uniformitarian  school 
that  is  even  more  significant  than  that  gained  in  the  case  of  the 
antecedent  rivers ;  for  in  one  case  a  growing  mountain  range  is 
subdued  by  the  concentrated  discharge  of  a  large  drainage  area, 
but  in  the  other  case  the  mountain  slowly  melts  away  under  the 
attacks  of  the  weather  alone  on  the  headwater  slopes  of  the 
growing  valleys. 

The  reason  why  all  these  studies  of  land  carving  are  of  impor- 
tance to  the  geographer  is  that  they  greatly  enlarge  the  number 
of  type  forms  that  he  may  use  in  descriptions,  and  that  they 
recognize  the  natural  correlations  among  various  forms  which 
must  otherwise  be  set  forth  in  successive  itemized  statements. 
The  brief  terminology  learned  in  early  school  days,  somewhat 
enlarged  by  a  more  mature  variety  of  adjectives,  is  usually  the 
stock  of  words  with  which  the  explorer  tries  to  reproduce  the 
features  of  the  landscapes  that  he  crosses,  and  as  a  result  his 
descriptions  are  often  unintelligible  ;  the  region  has  to  be  ex- 
plored again  before  it  can  become  known  to  those  who  do  not 
see  it.  The  longitudinal  relief  of  certain  well-dissected  coastal 
plains,  or  the  half-buried  ranges  of  certain  interior  aggraded 
basins,  may  be  taken  as  examples  of  forms  which  are  easily 
brought  home  and  familiarized  by  explanation,  but  which  com- 
monly remain  remote  and  unknown  under  empirical  description. 

It  may  be  urged  that  in  many  geological  discussions  from 
which  geography  has  taken  profit,  consideration  is  given  to 
form-producing  processes  rather  than  to  the  forms  produced. 
This  was  natural  enough  while  the  subject  was  in  the  hands  of 
geologists ;  but  geographers  should  take  heed  that  they  do  not 
preserve  the  geological  habit.  The  past  history  of  land  forms 
and  the  action  upon  them  of  various  processes  by  which  exist- 
ing forms  have  been  developed,  are  pertinent  to  geography  only 
in  so  far  as  they  aid  the  observation  and  description  of  the 
forms  of  to-day. 

Further  illustration  of  the  growing  recognition  of  form  as  the 
chief  object  of  the  physiographic  study  of  the  lands  is  seen  in 
the  use  of  the  term  "  geomorphology "  by  some  American 
writers ;  but  more  important  than  the  term  is  the  principle 


84  EDUCATIONAL   ESSAYS 

which  underlies  it.  This  is  the  acceptance  of  theorizing  as  an 
essential  part  of  investigation  in  geography,  just  as  in  other 
sciences.  All  explanation  involves  theorizing.  When  theory  is 
taken  piecemeal  and  applied  only  to  elementary  problems,  such 
as  the  origin  of  deltas,  it  does  not  excite  unfavorable  comment 
among  geographers.  But  when  the  explanation  of  more  compli- 
cated features  is  attempted,  and  when  a  comprehensive  scheme 
of  classification  and  treatment,  in  which  theorizing  is  fully  and 
frankly  recognized,  is  evolved  for  all  land  forms,  then  the  con- 
servatives recoil,  as  if  so  bold  a  proposition  would  set  them 
adrift  on  the  dangerous  sea  of  unrestrained  imagination.  They 
forget  that  the  harbor  of  explanation  can  only  be  reached  by 
crossing  the  seas  of  theory.  They  are  willing  to  cruise,  like  the 
early  navigators,  the  empirical  explorers,  only  close  along  shore, 
not  venturing  to  trust  themselves  out  of  sight  of  the  land  of 
existing  fact ;  but  they  have  not  learned  to  embark  upon  the 
open  ocean  of  investigation,  trusting  to  the  compass  of  logical 
deduction  and  the  rudder  of  critical  judgment  to  lead  them  to 
the  desired  haven  of  understanding  of  facts  of  the  past. 

One  of  the  bolder  explorers  of  the  high  seas  of  theory  is 
Powell,  who  defined  in  the  term  "  base-level "  an  idea  that  had 
long  been  more  or  less  consciously  present  in  the  minds  of  geol- 
ogists, and  which  has  been  since  then  of  the  greatest  service  to 
physiographers.  Powell  and  his  followers,  especially  Gilbert, 
Button,  and  McGee,  have  consistently  carried  the  consequences 
of  subaerial  erosion  to  their  legitimate  end  in  a  featureless  low- 
land, and  have  recognized  the  controlling  influence  of  the  base- 
level  during  all  the  sequence  of  changes  from  the  initial  to  the 
ultimate  form.  It  is  not  here  essential  whether  such  a  feature- 
less lowland  exists  or  ever  has  existed,  but  it  is  absolutely  essen- 
tial to  follow  the  lead  of  deduction  until  all  the  consequences  of 
the  theory  of  erosion  are  found,  and  then  to  accept  as  true 
those  theoretical  deductions  which  successfully  confront  the 
appropriate  facts  of  observation.  Only  in  this  way  can  the  error 
of  regarding  geography  as  a  purely  observational  natural  science 
be  corrected.  Following  the  acceptance  of  the  doctrine  of  base- 
levels  came  the  method  of  reconstituting  the  original  form  initi- 
ated by  deformation,  as  a  means  of  more  fully  understanding  the 


THE  PHYSICAL  GEOGRAPHY  OF  THE   LANDS         85 

existing  form ;  for  only  by  beginning  at  the  initial  form  can  the. 
systematic  sequence  of  the  changes  wrought  by  destructive  proc- 
esses be  fully  traced  and  the  existing  form  appreciated.  This 
had  often  been  done  before  in  individual  cases,  but  it  now  became 
a  habit,  an  essential  step  in  geomorphological  study.  Naturally 
enough,  the  terms  of  organic  growth,  such  as  young,  mature, 
old,  revived,  and  so  on,  came  to  be  applied  to  stages  in  the 
development  of  inorganic  forms ;  and  thus  gradually  the  idea 
of  the  systematic  physiographic  development  of  land  forms  has 
taken  shape.  This  idea  is  to-day  the  most  serviceable  and  com- 
pact summation  of  all  the  work  of  the  century  on  the  physical 
geography  of  the  lands.  It  recognizes  the  results  of  deformation 
in  providing  the  broader  initial  forms  on  which  details  are  to  be 
carved.  It  gives  special  attention  to  the  work  of  destructive 
processes  on  these  forms,  and  especially  to  the  orderly  sequence 
of  various  stages  of  development,  recognizing  that  certain  fea- 
tures are  associated  with  youth,  and  others  with  maturity  and 
old  age.  It  gives  due  consideration  to  the  renewed  movements 
of  deformation  that  may  occur  at  any  stage  in  the  cycle  of 
change,  whereby  a  new  sequence  of  change  is  introduced.  It 
gives  appropriate  place  not  only  to  the  forms  produced  by  the 
ordinary  erosive  action  of  rain  and  rivers,  but  to  the  forms  pro- 
duced by  ice  and  by  wind  action  as  well ;  and  it  coordinates  the 
changes  that  are  produced  by  the  sea  on  the  margin  of  the  land 
with  the  changes  that  are  produced  by  other  agencies  upon  its 
surface.  It  considers  not  only  the  various  forms  assumed  by 
the  water  of  the  land,  such  as  torrents,  rapids,  falls,  and  lakes, 
appropriately  arranged  in- a  river  system  as  to  time  and  place, 
but  also  the  forms  assumed  by  the  waste  of  the  land,  which, 
like  the  water,  is  on  its  way  to  the  sea.  In  a  word,  it  lengthens 
our  own  life,  so  that  we  may,  in  imagination,  picture  the  life  of 
a  geographical  area  as  clearly  as  we  now  witness  the  life  of  a 
quick-growing  plant,  and  thus  as  readily  conceive  and  as  little  con- 
fuse the  orderly  development  of  the  many  parts  of  a  land  form, 
its  divides,  cliffs,  slopes,  and  water  courses,  as  we  now  distinguish 
the  cotyledons,  stem,  buds,  leaves,  flowers,  and  fruit  of  a  rapidly 
maturing  annual  that  produces  all  these  forms  in  appropriate 
order  and  position  in  the  brief  course  of  a  single  summer. 


86  EDUCATIONAL  ESSAYS 

The  time  is  ripe  for  the  introduction  of  these  ideas.  The 
spirit  of  evolution  has  been  breathed  by  the  students  of  the  gen- 
eration now  mature  all  through  their  growing  years,  and  its  appli- 
cation to  all  lines  of  study  is  demanded.  It  is  true  that  the 
acceptance  of  inorganic  as  well  as  of  organic  evolution  is 
often  implied  rather  than  outspoken ;  yet  evolution  is  favorably 
regarded,  as  is  proved  by  the  eagerness  with  which  even  school 
boards  and  school-teachers,  conservatives  among  conservatives, 
hail  the  appearance  of  books  in  which  the  new  spirit  of  geogra- 
phy is  revealed.  In  the  last  years  of  the  century,  the  school- 
books  most  widely  used  in  this  country  have  made  great  advance 
in  the  explanatory  treatment  of  land  forms.  Tarr's  physical 
geographies  and  Russell's  monographic  volumes  on  the  "  Lakes," 
"  Glaciers,"  "  Volcanoes,"  and  "  Rivers  "  of  North  America,  all 
presenting  land  forms  in  an  explanatory  rather  than  an  empirical 
manner,  have  been  warmly  welcomed  in  this  country.  Penck's 
"  Morphologic  der  Erdoberflache  "  (1894),  although  largely  con- 
cerned with  the  historical  development  of  the  subject,  presents 
all  forms  as  the  result  of  process.  De  Lapparent's  "  Legons  de 
geographic  physique"  (1886)  treats  land  forms  genetically;  and 
a  second  edition  of  the  book  is  called  for  soon  after  the  first. 
"  Earth  Sculpture,"  by  James  Geikie  (1899),  and  Marr's  "  Scien- 
tific Study  of  Scenery"  (1900)  carry  modern  ideas  to  British 
readers.  The  books  of  the  coming  century  will  certainly  extend 
the  habit  of  explanation  even  further  than  it  has  yet  reached. 

This  review  of  the  advance  of  the  century  in  the  study  of 
land  forms,  the  habitations  of  all  the  higher  forms  of  life,  might 
have  been  concerned  wholly  with  the  concrete  results  of  explo- 
ration, as  was  implied  in  an  earlier  paragraph.  Travels  in  the 
Far  East  of  the  Old  World,  or  in  the  Far  West  of  the  New, 
have  yielded  facts  enough  to  fill  volumes.  But  such  a  view  of 
the  century  has  been  here  replaced  by  another,  not  because 
the  first  is  unimportant,  —  for  it  is  absolutely  essential,  —  but 
because  the  second  includes  the  first  and  goes  beyond  it.  Not 
the  facts  alone,  but  the  principles  that  the  facts  exemplify, 
demand  our  attention.  These  principles,  founded  upon  a  multi- 
tude of  observations,  are  the  greater  contribution  of  the  closing 
to  the  opening  century  in  the  study  of  the  forms  of  the  land. 


IV 

THE  TEACHING  OF  GEOGRAPHY 
THE  PHYSICAL  BASIS  OF  DESCRIPTIVE  GEOGRAPHY 

Several  valuable  books  on  methods  of  teaching  geography 
have  been  written  in  recent  years,  giving  emphasis  to  various 
matters  of  importance.  One  shows  that  the  home  district  should 
furnish  the  first  examples  on  which  geographical  descriptions 
are  based,  and  that  a  knowledge  of  the  examples  should  precede 
a  definition  of  the  terms  by  which  they  are  named.  Another 
calls  for  an  extension  of  physical  geography  at  the  expense  of 
political  geography.  A  third  justly  maintains  the  need  of  intro- 
ducing fresh  material  from  various  sources  in  addition  to  the 
brief  statements  of  the  text-book.  We  have  among  our  New 
England  teachers  successful  exponents  of  all  these  principles, 
and  the  newer  text-books  are  to  a  moderate  extent  adjusted  to 
them.  But  there  is  another  principle  that  has  not,  it  seems  to 
me,  received  sufficient  consideration.  This  is  the  importance  of 
the  more  advanced  study  of  physical  geography  by  all  teachers 
of  geography  in  any  of  its  branches,  even  by  those  who  have 
only  elementary  school  work  to  carry  on. 

All  good  teaching  requires  that  the  teacher  should  possess  a 
sound  knowledge  of  his  subject,  beyond  the  limits  of  his  class 
work.  Live  teaching  excites  questions  from  the  scholars,  and 
thus  leads  to  verbal  excursions  from  the  immediate  subject  in 
hand.  When  well  managed,  such  excursions  are  of  great  value, 
because  they  spring  from  the  pupil's  desire,  and  not  merely  from 
the  teacher  or  the  text-book.  Good  answers  to  such  questions 
can  come  only  from  the  background  of  knowledge  in  the  teacher's 
mind.  They  cannot  be  supplied  by  pedagogical  methods,  or  by 
text-books,  or  by  uncandid  pretensions  on  the  part  of  the  teacher, 
so  soon  apparent  to  his  class.  I  have  no  sympathy  whatever 
with  the  belief  sometimes  encountered  that  methods  will  make 

8? 


88  EDUCATIONAL  ESSAYS 

up  for  want  of  knowledge ;  or  with  the  more  prevalent  impres- 
sion that  knowledge  will  replace  method.  Of  the  two,  knowledge 
is  undoubtedly  the  more  important  and  should  come  first ;  but  a 
proper  understanding  of  both  is  the  desideratum.  In  this  paper 
I  wish  to  consider  one  element  of  the  knowledge  that  teachers 
of  geography  should  acquire ;  namely,  the  kind  of  information 
required  in  order  that  the  facts  and  principles  of  physical  geogra- 
phy may  be  clearly  presented.  I  choose  this  subject  because  of 
the  increasing  attention  given  in  recent  years  to  physical  over 
simply  descriptive  and  political  geography,  and  also  because 
the  text-books  and  hand-books  to  which  teachers  are  accustomed 
to  refer  do  not  seem  to  me  to  present  the  principles  of  physical 
geography  in  a  satisfactory  manner. 

Let  me  illustrate  by  some  specific  examples.  Take  four  great 
waterfalls.  The  lofty  fall  of  the  Yosemite  valley  leaps  in  a 
.slender  current  over  the  precipitous  wall  of  that  extraordinary 
chasm  and  plunges  sixteen  hundred  feet  before  its  scattered 
mists  gather  again  for  further  flow  as  a  stream.  The  world- 
renowned  Niagara  descends  in  great  volume  over  a  limestone 
ledge  into  the  gorge  below.  The  Shoshone  falls,  on  the  river 
of  that  name  in  Idaho,  drop  from  one  gorge  into  a  deeper  one 
over  a  sheet  of  lava.  The  rapids  known  as  the  first  cataract  of 
the  Nile  roll  and  toss  over  ledges  of  crystalline  rocks  that  inter- 
rupt the  generally  smooth  course  of  that  great  river.  With  which 
of  these  shall  we  compare  the  falls  of  the  Merrimac,  by  whose 
power  the  looms  of  Lowell  are  driven  ?  Shall  the  comparison 
be  made  as  to  height,  as  to  volume,  or  as  to  origin  and  physical 
conditions  ?  The  latter  is  the  only  natural  ground  for  geograph- 
ical comparison. 

The  Yosemite  fall  leaps  into  a  deep  valley  which  its  waters 
had  no  share  in  making.  The  stream  did  not  produce  the  cliff 
over  which  it  falls.  A  little  notch  has  been  cut  at  the  top,  but 
the  cliff  as  a  whole  was  ready-made  for  the  stream  to  fall  over. 
Niagara  has  indeed  cut  more  than  a  notch.  It  has  cut  a  gorge 
seven  miles  long  in  the  limestone  capping,  all  the  way  back  from 
the  bluffs  at  Lewiston ;  but  the  river  did  not  make  the  bluffs 
where  the  falls  started.  The  bluffs  are  of  much  greater  age 
than  the  river.  Its  current  was  turned  over  them  long  after 


THE  TEACHING  OF  GEOGRAPHY         89 

their  form  was  gained.  They  are  not  river-made,  nor  are  they 
like  in  origin  to  the  cliffs  of  the  Yosemite.  The  Shoshone  falls 
are  river-made  through  and  through.  The  river  there  began  a 
new  course  on  a  flat  lava  plain.  As  its  channel  was  deepened, 
the  harder  lava  flows  were  cut  through  near  the  surface  and  the 
looser  materials  beneath  were  then  worn  out  more  quickly.  The 
falls  began  where  the  waters  dropped  from  one  level  to  another. 
Since  they  first  appeared,  the  gorge  has  been  lengthened  back- 
ward many  miles,  like  a  ditch  cut  at  the  end.  The  river  found 
the  country  featureless,  and  in  the  little  advance  that  has  as  yet 
been  made  in  carrying  away  the  lava  plain  and 'reducing  it  all  to 
sea  level,  the  water  has  by  its  own  action  made  its  falls.  The 
rapids  of  the  Nile  are  of  quite  another  class.  On  either  margin 
of  the  valley  of  the  Nile  may  be  seen  the  horizontal  edges  of 
bedded  rocks  which  once  stretched  all  across  the  valley  from 
side  to  side.  The  river  at  first  flowed  over  their  surface,  then 
cut  its  channel  down  through  them,  and  at  a  certain  depth  un- 
expectedly encountered  a  buried  ledge  of  hard  crystalline  rocks  ; 
a  portion  of  an  old  buried  land,  and  probably  an  old  hilltop, 
which,  by  reason  of  its  height  above  the  buried  lowlands  there- 
abouts, was  first  encountered  by  the  down-cutting  river.  This 
obstacle  produced  the  rapids  ;  they  are  not  steep,  because  the 
slope  of  the  old  buried  hill  is  gentle,  as  far  as  it  is  uncovered. 

The  falls  of  the  Merrimac  at  Lowell,  at  Manchester,  and  at 
various  other  points;  the  falls  of  the  Connecticut  at  Turner's 
Falls,  at  Holyoke,  and  elsewhere,  are  closely  related  to  the  cata- 
racts of  the  Nile.  It  is  not  true  that  the  whole  of  the  old  country 
on  which  the  ancestors  of  the  Merrimac  and  the  Connecticut 
once  flowed  has  been  buried,  but  the  valleys  of  the  ancient 
rivers  have  been  buried  even  to  a  depth  of  three  or  four  hun- 
dred feet  by  a  filling  of  clay,  sand,  and  gravel  that  was  washed 
into  them.  These  deposits  covered  many  a  rugged  ledge  and 
rocky  spur  on  the  slopes  of  the  ancient  valleys,  and  when  the 
rivers  at  a  later  time  turned  to  cleaning  out  the  clogging  of 
gravel  and  sand,  they  lighted  unawares,  like  the  Nile,  on  various 
buried  ledges.  The  Merrimac  thus  developed  its  falls  at  Man- 
chester, or  perhaps  I  should  say,  Manchester  developed  at  the 
falls  ;  and  the  same  way  again  with  Lowell,  Lawrence,  and  many 


90  EDUCATIONAL  ESSAYS 

busy  villages.  The  Connecticut  likewise  uncovered  various  buried 
ledges,  at  nearly  all  of  which  there  are  now  manufacturing  towns 
and  cities.  New  England  enterprise  has  known  how  to  take  good 
advantage  of  these  river  accidents.  Now  it  is  perfectly  true 
that  the  water  power  developed  in  a  river  of  a  given  volume, 
falling  a  certain  height,  is  the  same  whether  the  fall  originates 
in  one  way  or  another.  The  height  of  the  falls  is  indeed  an 
important  matter ;  but  in  teaching  about  rivers,  the  teacher 
must  not  stop  with  numerical  statistics.  He  must  appreciate 
something  also  of  the  physical  history  of  the  rivers.  These 
alone  give  basis*  for  physical  comparisons. 

I  make  no  attempt  here  to  explain  in  full  these  different  kinds 
of  falls,  nor  to  state  the  reasons  for  the  conclusions  just  outlined. 
That  would  require  deliberate  study.  My  object  is  simply  to 
illustrate  what  is  meant  by  the  physical  basis  of  descriptive 
geography,  and  to  show  by  immediate  example  what  kind  of 
information  on  such  subjects  every  teacher  of  geography  should 
possess  in  order  to  answer  the  questions  from  his  class  with 
enlivening  fullness  and  to  place  the  principles  of  the  subject 
clearly  before  his  pupils.  Perhaps  the  teacher  might  not  have 
in  mind  the  particular  examples  of  river  development  here  pre- 
sented ;  but  they  nevertheless  illustrate  the  kind  of  knowledge 
that  he  should  gain.  They  serve  also  to  illustrate  in  a  definite 
way  what  kind  of  geographical  information  a  person  should  gain 
if  he  studies  at  a  university  with  the  idea  of  preparing  himself 
to  teach  geography.  The  examples  cited  are  taken  directly  from 
among  many  others  that  constitute  the  subjects  of  elementary 
lectures  to  college  students.  I  believe  that  a  large  fund  of  this 
kind  of  information  should  be  in  mind  before  one  need  give 
much  attention  to  methods  of  teaching  geography. 

It  must  be  borne  in  mind  that  it  is  not  supposed  for  a  mo- 
ment that  every  teacher  who  has  learned  such  facts  as  these 
would  forthwith  teach  them  to  his  classes.  They  are  not  his 
weapons,  but  his  armor.  They  constitute  the  foundation  of 
his  knowledge,  on  which  he  can  build  explanatory  stories  in 
his  many  times  of  need.  He  may,  for  example,  be  telling  his 
class  how  it  happens  that  the  capital  of  New  Jersey  is  located 
at  a  certain  point  on  the  Delaware,  where  there  are  rapids  at 


THE  TEACHING  OF  GEOGRAPHY  91 

th'e  head  of  tide  water.  He  may  refer  to  the  growth  of  Rochester 
in  western  New  York  at  the  powerful  falls  of  the  Genesee.  He 
may  wish  to  mention  the  many  towns  and  cities  of  the  West 
that  have  grown  up  at  the  falls  and  rapids  of  rivers;  as,  for 
example,  Louisville,  Minneapolis,  Grand  Rapids,  Sauk  Rapids, 
Rapid  City,  and  Great  Falls.  He  may  wish  to  explain  why  water- 
power  towns  are  absent  in  certain  parts  of  the  country,  and 
comment  on  the  consequent  distribution  of  manufacturing  indus- 
tries. In  all  this  he  will  find  satisfaction,  and  his  class  will  find 
entertainment  and  bright  instruction,  if  he  addresses  them  as 
one  who  is  well  informed  beyond  the  page  of  his  text-book  and 
who  knows  more  than  he  tells. 

The  teacher  of  geography,  if  he  would  be  successful,  must  not 
stop  with  the  elementary  explanations  that  are  given  in  the  text- 
books of  the  day.  He  must  be  sufficiently  informed  to  expound 
the  text  of  the  books.  If  his  class  reads  of  the  recession  of 
Niagara  and  the  consequent  future  draining  of  the  level  plain 
now  drowned  under  lake  Erie,  let  him  emphasize  the  story  by 
telling  of  the  broad  lacustrine  plain  of  the  Red  river  of  the 
North,  laid  open  by  the  melting  away  of  an  icy  barrier  over 
Canada  that  not  long  ago  held  up  an  extended  sheet  of  water 
where  there  are  now  rich  wheat  fields.  When  his  pupils  read  of 
the  erosion  of  valleys,  of  which  all  the  books  now  make  some 
mention,  he  must  tell  of  the  canon  of  the  Colorado  as  an  in- 
stance of  a  vast  erosive  work.  But  he  must  also  point  out  that, 
however  great  a  work  the  excavation  of  this  canon  is,  it  is  only 
the  beginning  of  the  mighty  task  that  awaits  the  river.  The 
canon  is  only  the  well-marked  waterway,  down  which  must  be 
carried  all  the  stupendous  mass  of  the  wasting  plateaus  on  either 
side.  The  teacher  should,  when  illustrating  the  vast  work  of 
erosion,  turn  from  a  canon,  however  deep,  and  look  at  the 
record  of  a  much  greater  destructive  work  near  at  home  in  the 
plateau  of  New  England,  —  the  reduced  remnant  of  a  once  great 
mountain  system,  now  laid  low.  Here  is  completed  the  work 
that  the  Colorado  has  only  just  begun.  If  the  class  learn,  as 
they  should,  of  our  Atlantic  coastal  plain  as  a  portion  of  the 
sea-tottom  lately  raised  and  laid  bare,  and  thus  exposed  to 
erosion  by  rain  and  rivers,  let  them  learn  also  of  old  lowlands, 


92  EDUCATIONAL  ESSAYS 

now  raised  to  highlands,  and  thus  exposed  to  a  renewed  attack 
from  the  agents  of  erosion.  This  again  may  be  illustrated  at 
home,  for  our  New  England  plateau  was  a  lowland  when  it  was 
worn  down  from  its  once  mountainous  height,  and  our  existing 
valleys  have  been  excavated  only  since  the  lowland  was  subse- 
quently elevated  to  a  higher  position,  as  a  gently  inclined  plateau, 
with  its  southern  and  eastern  margin  at  the  seashore,  thence 
rising  inland  until  it  reaches  an  altitude  of  fifteen  or  sixteen 
hundred  feet  in  the  northwestern  part  of  Massachusetts. 

Although  some  of  these  statements  may  seem  novel,  yet  they 
fall  directly  in  line  with  others  of  simpler  nature  that  are  not 
only  asked  for  from  teachers,  but  taught  to  young  pupils.  One 
of  the  most  earnest  advocates  of  a  rational  and  observational 
method  of  teaching  geography  urges  that  the  surface  of  the 
earth  should  be  described  as  that  of  a  living  organism.  He 
teaches  the  washing  of  soil  down  slopes  and  the  likeness  of  little 
deltas  to  great  alluvial  plains,  even  as  first  steps  in  elementary 
classes.  Such  a  beginning  is  excellent,  but  we  need  a  legiti- 
mate extension  of  this  beginning.  I  have  sometimes  ventured 
to  ask  a  teacher  questions  about  rivers  and  valleys,  such  as 
those  just  considered;  and  it  usually  appears  that  they  are  unfa- 
miliar matters.  Sometimes  they  are  regarded  as  irrelevant ;  as 
belonging  to  geology  perhaps,  but  not  germane  to  geography,  — 
the  "description  of  the  earth's,  surf  ace."  It  matters  little  under 
which  of  these  confluent  sciences  such  subjects  are  catalogued ; 
but  I  protest  emphatically  against  the  belief  that  they  are  beyond 
the  necessary  equipment  of  teachers  of  geography.  When  sand 
dunes  are  described,  the  most  elementary  teaching  of  geography 
does  not  hesitate  to  explain  their  origin  by  the  action  of  the  wind. 
Volcanoes  are  seldom  mentioned  without  some  reference  to  their 
origin  by  eruption  of  lava  and  ashes  from  a  deep-seated  source. 
Few  text-books  nowadays  omit  to  state  that  valleys  are  cut  out 
by  streams  ;  but  they  seldom  carry  the  same  explanation  to  its 
legitimate  end  and  mention  regions  where  the  valleys  have 
widened  so  far  as  to  consume  the  hills  and  reduce  the  region  to 
a  worn-out  lowland,  a  lowland  of  denudation.  Yet  the  relics  of 
such  lowlands  dominate  our  geographical  forms  to-day.  An  old 
lowland  of  denudation  now  uplifted  and  dissected  is  a  widespread 


THE  TEACHING  OF  GEOGRAPHY         93 

element  of  the  topographical  features  of  our  Atlantic  slope.  No 
just  comprehension  of  our  geography  can  be  gained  without 
some  appreciation  of  it.  What  I  lament  is  that  while  a  begin- 
ning of  physical  explanation  is  made,  it  is  not  carried  out 
systematically  and  seriously,  either  in  the  text-book  or  in  the 
preparation  of  the  teacher.  The  text-book  falls  short  of  its 
duty  in  failing  to  present  clearly  enough  the  real  meaning  of 
geographical  forms,  and  in  falling  behind  the  progress  of  geo- 
graphical science  in  such  matters.  The  teacher  too  often  halts 
with  the  text-book.  Many  of  the  principles  and  explanations  are 
not  too  difficult  for  children  to  understand.  They  are  readily 
accepted  when  presented  deliberately  and  in  gradual  succession, 
with  vivid  and  correct  illustrations. 

More  attention  to  physical  geography  is  called  for  by  all  the 
leading  writers  on  the  improvement  of  geographical  teaching. 
Further  study  in  this  direction  is  therefore  needed  by  those 
who  are  preparing  to  teach.  More  attention  to  the  home  dis- 
trict is  demanded  even  in  the  earliest  classes.  Better  training 
is  therefore  needed  in  the  appreciative  recognition  of  the  mean- 
ing of  the  physical  features  of  the  land  immediately  about  us ; 
for  wherever  the  teacher  goes,  his  geographical  laboratory  is  in 
the  fields  about  him,  and  he  must  be  prepared  to  solve  its 
problems  and  present  them  properly  to  his  classes. 

While  dwelling  on  the  importance  of  a  better  understanding 
and  teaching  of  physical  geography,  I  do  not  wish  to  underrate 
the  value  of  the  rational  teaching  of  political  and  descriptive 
geography.  Yet  it  does  seem  that  until  the  features  of  the 
earth's  surface,  the  fundamental  subject  of  geography,  are  well 
understood  in  their  natural  relations,  only  an  artificial  meaning 
can  attach  to  their  introduction  into  descriptive  geography.  It 
is  excellent  to  read  of  the  introduction  of  fresh  material  by 
teacher  and  pupil  into  the  descriptions  of  one  country  or  another. 
I  plead  for  the  same  freshness  and  originality  of  illustration  in 
teaching  about  the  physical  features  of  the  earth,  and  I  believe 
that  in  the  coming  years  a  much  greater  share  of  time  will  be 
allotted  to  this  division  of  the  subject  than  is  now  the  case. 

The  change  that  lies  in  the  future  for  physical  geography  has 
already  overtaken  the  biological  sciences.  The  brief  descriptions 


94  EDUCATIONAL  ESSAYS 

of  numerous  species  of  plants  and  animals,  which  children  once 
learned  under  the  name  of  Natural  History,  are  now  replaced 
by  the  careful  examination  of  a  few  forms,  chosen  to  illustrate 
broad  homologies.  Physics  and  chemistry  are  also  in  process 
of  liberation  from  text-book  control,  and  no  well-equipped  school 
where  these  subjects  are  taught  is  now  without  its  laboratory, 
in  which  simple  experiments  may  be  performed  by  the  pupils 
as  a  means  of  really  learning  the  fundamental  principles  of 
these  sciences.  The  beginnings  of  a  change  to  a  laboratory 
method  in  teaching  geography  are  seen  where  sand  and  clay 
models  are  used  ;  but  this  beginning  leaves  nearly  everything 
to  be  accomplished.  This  is  so  partly  because  the  means  of 
illustration  are  inadequate  and  cease  in  the  higher  classes,  where 
they  ought  to  be  extended  ;  and  partly  because  the  principles 
that  should  guide  the  preparation  of  illustrations  of  one  kind 
and  another  are  as  a  rule  so  little  considered. 

I  must  repeat,  in  order  not  to  be  misunderstood,  that  many 
subjects  and  illustrations,  which  are  here  referred  to  as  essential 
for  the  preparation  of  the  teacher,  should  not  be  known  in  order 
that  they  should  be  taught,  unless  in  the  higher  classes  of  the 
grammar  schools  or  in  high  schools.  They  should  be  known  in 
order  to  give  the  teacher  a  reserve  of  strength  with  which  to 
overcome  the  difficulties  of  his  elementary  work.  Let  me  again 
take  up  some  specific  illustrations. 

I  have  already  referred  to  the  brief  mention  that  is  made  in 
most  text-books  of  valleys,  and  sometimes  of  land  forms  in  gen- 
eral, as  the  product  of  erosion  of  a  once  larger  land  mass,  the 
waste  of  the  older  land  having  been  carried  by  rivers  to  the 
sea.  But  where  do  we  find  the  deserved  mention  of  the  forms 
assumed  by  the  waste  of  the  land  on  its  way  to  the  sea  ?  The 
land  waste  encumbers  the  mountain  sides,  forming  vast  talus 
slopes.  In  dry  climates  the  waste  extends  broadly  from  the 
base  of  the  mountains  over  the  lowlands  in  gently  inclined  plains. 
The  waste  often  clogs  rivers,  choking  up  their  valleys.  Where 
a  side  stream  brings  an  overload  of  waste  into  a  main  stream, 
it  builds  a  delta  at  the  junction,  just  as  the  main  stream  builds 
a  delta  at  its  mouth  in  standing  waste.  Indeed,  sometimes  the 
side  stream  chokes  up  the  main  river  and  converts  it  into  a  linear 


•THE  TEACHING  OF  GEOGRAPHY  95 

lake,  like  lake  Pepin,  a  beautiful  expansion  of  the  upper  Missis- 
sippi. I  have  told  children  of  this  lake ;  they  like  to  hear  of  it, 
and  its  meaning  is  not  beyond  their  comprehension.  In  direct 
contrast  with  the  case  of  lake  Pepin  is  that  in  which  a  fully 
loaded  main  stream  builds  up  its  flood  plain  with  the  excess  of 
land  waste  that  it  brings  down  from  its  head  waters.  The  flood 
plain  thus  rises  faster  than  the  plains  of  the  small  side  streams ; 
and  these,  not  having  enough  land  waste  with  which  to  build  up 
their  plains,  must  fill  their  valleys  with  water  up  to  the  level  of 
the  main  stream,  and  thus  form  lakes.  River  flood  plains  should 
be  regarded  simply  as  the  temporary  resting  place  of  the  excess 
of  waste  washed  into  the  river  by  the  decay  of  the  land.  Being 
composed  of  fine  materials,  they  are  fertile  regions,  as  in  the 
broad  bottom  lands  of  our  great  Mississippi.  Yet  they  may  be 
traced  back  by  gradual  changes  to  the  stony  talus  slopes  of  the 
mountain  sides,  with  which  they  are  in  many  ways  correlated.  A 
whole  series  of  interesting  comparisons  may  thus  be  introduced, 
each  one  having  for  its  object  the  illustration  of  some  otherwise 
barren  recitation  of  geographical  names.  Just  as  events  of  human 
history  serve  to  impress  the  relations  of  geographical  forms  on 
a  child's  memory,  so  the  events  in  the  history  of  the  forms  them- 
selves have  a  great  value  as  mnemonics.  They  give  a  sense  of 
reality  where  the  text-book  gives  little  more  than  words. 

Teachers  have  sometimes  asked  me  where  they  should  go  to 
find  illustrations  of  the  kind  here  named.  No  one  book  contains 
them.  Nothing  but  continual  searching,  reading,  and  studying 
will  secure  them. 

WHAT  TO  AVOID  IN  TEACHING  GEOGRAPHY 

The  subtitle  given  to  this  part  of  the  essay  expresses,  as 
briefly  as  possible,  a  few  general  considerations  that  I  wish  to 
present  in  contrast  to  those  discussed  above.  The  theme  there 
was,  in  effect,  What  should  the  teacher  know  ?  The  conviction 
that  he  should  be  informed  far  beyond  the  limits  of  his  teaching 
was  illustrated  by  bringing  forward  a  number  of  specific  examples 
of  the  kind  of  facts  that  I  think  every  live  teacher  should  have 
in  mind.  I  shall  now  consider  the  opposite  side  of  the  question, 


96  EDUCATIONAL  ESSAYS 

—  What  is  unnecessary,  or  unimportant,  or  injurious,  in  geo- 
graphical teaching  ?  The  undesirable  elements  encountered,  to 
a  greater  or  less  degree,  in  teaching  geography  are  divisible 
into  superfluities  and  errors.  I  shall  consider  a  number  of  these 
in  order. 

In  the  first  part,  the  chief  emphasis  was  given  to  the  impor- 
tance of  storing  the  teacher's  mind  with  facts  and  explanations 
on  the  physical  side  of  geography ;  not  that  other  sides  should 
be  overlooked,  but  that  I  found  space  for  illustration  of  only  one 
division  of  the  subject.  It  should  now  be  repeated,  as  was 
then  said,  that  knowledge  of  this  kind  is  not  to  be  discharged 
by  the  teacher  in  a  flood,  overwhelming  the  pupils  before  they 
can  appreciate  it,  but  that  it  should  be  presented  only  when 
called  for,  piecemeal,  slowly,  and  chiefly  in  the  way  of  illustrat- 
ing or  explaining  subjects  that  are  more  directly  pertinent  to 
the  usual  routine  of  the  study.  It  is  perhaps  not  often  that 
teachers  of  geography  should  be  advised  to  husband  their  infor- 
mation ;  and  yet  I  can  believe  that  a  well-taught  beginner  might 
overtask  his  class  with  an  exuberance  of  illustration,  making 
the  geographical  diet  too  rich  for  his  pupils.  An  excess  of  pre- 
cision is  also  to  be  avoided  ;  minuteness  of  knowledge  is  not  to 
be  expected  in  children.  Strong,  broad  descriptions  are  prefer- 
able, in  which  the  chief  elements  of  form,  area,  climate,  resources, 
and  population  are  linked  together  in  a  natural  and  effective 
way,  and  emphasized  by  illustration,  whereby  the  essentials  are 
easily  remembered  by  pupils  of  ordinary  ability.  Over-zeal,  lead- 
ing to  excess  in  quantity  or  precision,  is  characteristic  of  first 
efforts,  when  the  facts  of  the  subject  have  not  taken  positions 
proper  to  their  relative  importance.  There  is  a  want  of  perspec- 
tive in  such  teaching ;  matters  of  detail  are  brought  forward 
and  confused  with  larger  matters  of  much  greater  importance ; 
but  with  practice  this  mistake  disappears.  It  is  not  a  mistake 
of  the  kind  we  are  apt  to  suffer  from ;  and  I  mention  it  chiefly 
because  it  might  at  first  naturally  follow  from  the  acceptance  of 
the  advice  already  given,  to  the  effect  that  teachers  should  be 
widely  informed  before  beginning  to  teach. 

In  contrast  with  this,  I  may  mention  a  mistake  of  quite  another 
kind,  and  probably  the  most  serious  of  the  difficulties  that  now 


THE  TEACHING  OF   GEOGRAPHY 


97 


afflict  geography.  This  comes  with  teachers  whose  preparation 
is  insufficient.  They  feel  their  weakness.  They  see  necessity 
of  strengthening  their  teaching,  but  not  possessing  the  elements 
of  strength  in  themselves,  they  try  to  borrow,  and  then  too 
often  add  difficulty  instead  of  value  to  their  instruction.  It  is 
for  this  reason  that  there  is  so  much  useless  memorizing  in  the 
study  of  geography.  It  must  be  very  stupid  work  to  both 
teacher  and  pupils.  A  teacher  well  informed  on  the  subjects 
introduced  briefly  in  the  text-book  would  feel  choked  if  he  had 
no  opportunity  of  bringing  in  appropriate  side-illustrations  and 
explanations.  A  teacher  not  well  informed  has  no  sufficient 
fund  of  illustrations  with  which  to  refresh  the  tiresome  facts  of 
the  page,  and  therefore  they  alone  constitute  the  subject  of  his 
teaching.  Too  great  stress  is  then  necessarily  laid  on  verbatim 
recitations,  for  there  is  nothing  else  with  which  to  occupy  the 
time.  This  is  a  sad  difficulty,  and  it  attends  poor  teaching  in 
all  subjects.  I  know  of  a  case  in  which  a  teacher  of  history, 
feeling  that  his  class  was  not  doing  work  enough,  required  each 
student  to  memorize  the  names  and  dates  of  the  popes,  in  order 
to  give  more  body  to  the  class  work,  —  a  poverty-stricken  expedi- 
ent. I  have  been  told  of  another  case  in  which  a  class  in  geology 
had  to  recite  from  Dana's  "  Manual  of  Geology,"  word  for  word, 
—  a  most  shocking  misuse  of  that  excellent  compendium.  Is 
there,  however,  any  subject  in  which  this  error  is  so  common  as 
in  geography  ?  It  is  not  alone  the  fault  of  the  teachers,  as  many 
text-books  are  evidently  prepared  with  the  idea  that  every  word 
is  to  be  learned.  How,  except  by  rote,  could  a  scholar  make 
intelligent  report  of  such  a  paragraph  as  this,  extracted  from  a 
well-known  English  text-book  of  physical  geography : 

The  Danube  receives  a  large  number  of  tributaries,  of  which  the  most 
important  are,  on  the  right,  the  Isar,  Inn,  Raab,  Drave,  Save,  Morave,  and 
Isker.  On  the  left  are  the  Altmiihl,  Regen,  Waag,  Gran,  Theiss,  Temes, 
Aluta,  Sereth,  and  Pruth.  Many  of  these  are  large  streams  with  other  im- 
portant tributaries.  The  Danube  drains  upwards  of  300,000  square  miles 
of  country. 

Pages  could  be  filled  with  quotations  of  that  kind ;  yet  to 
what  do  they  lead  ?  If  it  be  conceived  that  any  one  should  ever 
wish  to  memorize  facts  so  unimportant,  let  them  be  learned  from 


98  EDUCATIONAL  ESSAYS 

the  map,  where  they  are  more  expressive  than  in  a  printed  list. 
If  it  is  important  for  the  tributaries  of  all  rivers  to  be  stated 
outside  of  the  maps,  place  them  in  tabular  form,  and  utilize  the 
space  thus  gained  by  inserting  something  worth  remembering 
about  one  or  another  of  the  examples,  —  something  that  is  not 
better  presented  in  maps  or  tables.  It  is  sad  to  think  of  children 
being  perplexed  with  such  stuff  as  is  given  in  the  above  quota- 
tion, yet  the  book  from  which  it  is  taken  reached  a  fifth  edition 
only  twenty  years  ago. 

It  should  be  noticed  that  the  correction  of  this  error  does  not 
lie  so  much  in  the  substitution  of  one  text-book  for  another,  as 
they  are  now  constituted,  but  in  the  improved  use  of  books  by  giv- 
ing less  attention  to  the  unimportant  paragraphs.  This  correction 
is  in  the  hands  of  the  teacher  ;  he  must,  from  his  own  knowledge, 
aided  by  wall  maps  and  the  school  library,  relieve  the  monotony 
of  text-book  teaching.  If  I  should  condense  into  the  fewest 
words  the  intent  of  this  part  of  my  argument,  they  would  be  : 
"  Avoid  verbatim  recitations;  put  something  of  life  and  nature 
into  teaching." 

Between  the  two  extremes  of  superabundance  and  barrenness, 
a  middle  path  must  be  selected  by  experience  and  good  judg- 
ment. Facts  that  appear  isolated  must  be  bound  together  in 
their  true  relations  ;  trivial  matters  must  be  lightly  passed  over ; 
matters  of  importance,  in  which  the  class  finds  difficulty,  must 
be  kept  in  hand  and  expounded  till  familiar.  The  best  results 
of  such  a  method  can  be  gained  only  by  a  judgment  so  good 
and  an  experience  so  long  that  nothing  but  the  truly  professional 
spirit  of  teaching,  entered  on  as  a  life  work,  will  insure  the  im- 
provement that  we  all  desire  and  strive  for. 

Lest  some  might  misinterpret  what  I  have  just  said,  to  mean 
that  all  memorizing  of  the  facts  of  geography  should  be  omitted, 
I  must  state  explicitly  that  in  geography,  as  in  spelling,  there 
seems  to  be  no  way  of  avoiding  a  large  amount  of  memorizing, 
if  the  pupil  is  to  have  a  sufficient  fund  of  information  with  which 
to  extend  his  own  experience  in  later  life.  The  labors  of  English 
spelling  can  be  lightened  by  grouping  words  of  similar  deriva- 
tion, as  I  used  to  learn  them  in  my  "Scholar's  Companion"; 
but  I  cannot  imagine  any  method  by  which  the  labor  of  learning 


THE  TEACHING  OF  GEOGRAPHY 


99 


to  spell  can  be  entirely  done  away  with.  So  with  geography  ;  it 
is  essential  that  every  child  should  learn  the  names  and  positions 
of  the  larger  geographical  elements  ;  but  to  learn  them  simply 
as  recitations  of  words  printed  in  a  book  is  a  fatal  mistake. 
Several  years  must  be  included  in  the  geographical  course, 
during  which  the  world  has  to  be  gone  over  and  over,  with  more 
care  and  thoroughness  at  each  repetition,  before  the  familiarity 
that  we  all  should  have  with  it  can  be  gained.  This  labor  cannot 
be  omitted,  but  it  may  be  lightened  by  judicious  illustration. 
Still,  there  is  no  royal  road.  I  have  no  recipe  by  which  all  but 
the  easy  parts  of  the  subject  can  be  omitted  and  yet  have  the 
pupil  well  taught.  Wide  information  on  the  part  of  the  teacher 
and  attentive  effort  on  the  part  of  the  pupil  are  essentials  to 
success ;  but  the  labor  thus  thrown  on  both  need  not  be  dull 
and  stupefying. 

How  shall  the  teacher  know  what  need  not  be  taught  ?  What 
are  the  unessentials  in  the  routine  work  of  geographical  teach- 
ing ?  We  may  learn  something  here  by  asking  one  another  a 
series  of  questions  that  children  may  have  to  learn  at  school. 
The  small  value  of  some  of  the  questions  is  not  so  well  indicated 
by  our  having  forgotten  the  answers  as  by  our  not  caring  if  we 
have  forgotten.  It  is  natural  enough  that  many  things  learned 
at  school  should  be  forgotten  afterward  when  the  mind  is  occu- 
pied with  other  things.  It  must  not  be  inferred  that  Latin  and 
Greek  should  not  be  studied  in  school  because  they  are  after- 
ward forgotten  ;  we  are  sorry  enough  if  we  cannot  translate 
from  the  ancient  languages  when  we  meet  them  in  words  or 
passages.  But  this  is  not  the  case  with  the  names  of  the 
branches  of  the  Danube.  Who  cares  whether  he  can  at  call 
repeat  them  in  order  ?  He  may  know  that  the  Inn  comes  in 
from  the  Alps  and  the  Theiss  from  the  plains  of  Hungary ;  the 
others  may  be  looked  for  on  a  map  if  they  are  wanted.  It  is 
this  indifference  to  the  facts  of  routine  geography  that  tells  us  of 
their  small  value.  It  is  the  easy  recovery  of  them,  when  desired, 
that  makes  the  memorizing  of  their  names  so  useless.  They 
appear  clearly  enough  on  the  maps.  Leave  them  there  till 
wanted,  and  select  from  the  many  a  few  about  which  something 
more  than  a  name  can  be  given  ;  not  that  name  and  incident 


100  EDUCATIONAL  ESSAYS 

both  need  to  be  learned  by  heart,  but  that  the  incident  supplied 
by  the  teacher  serves  as  a  little  barb  to  hold  the  fact  in  the 
memory.  If  the  teacher,  with  all  his  preparation,  has  no  inci- 
dent or  illustration  pertinent  to  the  facts,  let  them  pass  hardly 
noticed;  if  they  are  so  unimportant  that  he  knows  nothing 
more  than  their  name  and  place,  as  given  on  the  map,  and  as 
any  one  might  know  them,  in  spite  of  his  having  given  time  to 
careful  preparation  on  the  various  sides  of  geographical  study, 
then  omit  them  and  turn  the  attention  of  the  class  to  something 
that  he  can  tell  more  about.  It  may  be  that  the  choice  of  sub- 
jects made  by  the  teacher  will  not  always  include  the  most 
important  places  and  subjects,  but  it  should  at  least  include 
the  things  he  can  best  teach ;  and,  as  such,  the  things  of  the 
highest  value  to  the  class  under  his  instruction. 

The  incidents,  illustrations,  and  explanations  to  which  I  have 
repeatedly  referred  should  be  introduced  not  only  to  help  the 
pupil's  memory  but  also  to  increase  the  reality  of  the  subjects 
that  are  studied.  Take  care  that  the  names  learned  from  the 
text  or  the  map  represent  places  and  things,  and  not  words  or 
lines.  We  have  all  heard  of  the  man  who  confessed  that  his 
chief  recollection  of  Austria  was  as  a  red  patch  on  the  map 
hanging  on  his  schoolroom  wall.  Last  summer  I  heard  of  a 
similar  example.  A  little  boy  was  watching  his  aunt  draw  and 
color  a  map  of  the  United  States ;  when  Ohio  was  reached  and 
a  blue  tint  given  to  it  the  boy  exclaimed,  "Ohio* is  not  blue; 
it  is  green."  Emphasis  in  his  teaching  had  been  given  to  the 
unrealities  of  geography. 

There  is  now  less  reason  than  existed  formerly  for  urging 
the  postponement  of  astronomical  and  mathematical  geography 
till  the  later  years  of  study.  Teachers  generally  agree  that  a 
beginning  must  not  be  made  on  the  unseen,  but  on  the  visible 
facts  and  forms  of  the  school  district.  Still,  even  young  pupils 
may  at  an  early  age  become  familiar  with  the  earth  as  a  globe, 
with  the  idea  of  passing  over  its  great  rotundity  and  reaching 
one  land  after  another.  It  is  not  this  so  much  as  the  ideas  of 
poles  and  equator,  latitude  and  longitude,  that  may  well  be 
delayed  till  the  general  distribution  of  lands  and  oceans  is 
learned.  The  seasons,  the  noon  altitude  of  the  sun,  the  varying 


THE  TEACHING  OF  GEOGRAPHY  IOI 

length  of  the  day  and  night,  are  subjects  that  can  be, best  tough  c 
by  observation.  Let  the  members  of  the  class  be  required  to 
contribute  records  for  a  school  journal,  to  be  kept  continuously 
for  a  number  of  years.  Let  them  thus  accumulate  facts  from 
which  they  may  discover  for  themselves  the  dates  of  high  and 
low  sun,  of  long  and  short  days.  Do  not  rob  them  of  the  oppor- 
tunity of  discovering  simple  correlations,  as  open  as  these  are 
to  elementary  investigation.  Let  them  study  out  the  phases  of 
the  moon.  From  the  records  thus  obtained,  ask  a  class  if  they 
can  tell  how  much  farther  away  the  sun  is  than  the  moon.  If  the 
school  is  on  tide  water,  let  it  be  the  duty  of  the  members  of  the 
class  in  rotation  to  detect  the  time  and  height  of  high  and  low 
water,  and  correlate  these  changes  with  the  movements  of  the 
moon  and  sun.  Let  them  thus  learn  the  important  lesson  that 
the  world  is  wide  open  to  their  individual  study,  and  that  great 
reward  follows  the  attentive  use  of  their  opportunities.  The 
quantity  of  facts  secured  may  be  in  the  end  less  than  those 
recited  in  a  few  days,  parrot  fashion,  from  an  unmeaning  page  ; 
but  the  quality  of  the  facts  learned  by  individual  observation 
more  than  makes  up  for  their  lessened  quantity. 

Directly  in  connection  with  the  above  is  the  suggestion  that 
technical  terms  should  be  delayed  until  the  ideas  that  they  rep- 
resent have  become  familiar  from  observation  or  description. 
Leave  definitions,  which  always  represent  generalizations,  until 
the  mind  is  familiar  with  the  facts  that  call  for  comparison 
and  definition.  Avoid  the  appeal  to  authority  as  justification 
for  any  statement  unless  good  reason  goes  with  it.  Do  not 
often  introduce  personal  authority  in  elementary  teaching.  Do 
not  say,  "  In  Ganot's  treatise  on  physics,  as  edited  by  Professor 
Atkinson,  the  following  remarks  are  made  on  this  head  "  ;  or, 
"  Mr.  R.  H.  Scott  gives  the  following  statements  from  Mohn's 
treatise."  All  these  names  are  excellent  sources  for  quotation; 
but  young  pupils  should  not  be  troubled  by  the  interruption  of 
the  ideas  that  such  sentences  cause.  This  appeal  to  authority 
tends  to  subordinate  exactly  the  spirit  of  rational  independence 
that  should  be  encouraged.  If  the  statements  that  are  to  be 
quoted  are  not  self-explanatory,  their  explanation,  but  not  their 
authors,  should  be  given. 


itte  EDUCATIONAL  ESSAYS 

,  ;  Avoid-  hobbies. «  Do  not  be  too  methodical,  too  logical.  Do 
not  try  to  compress  the  variety  of  nature  into  rigid  and  artifi- 
cial concepts,  types,  and  diagrams.  Generalization  is,  of  course, 
an  important  aid  in  expressing  the  recurrence  of  a  series  of 
similar  phenomena ;  but  when  it  becomes  more  complicated 
than  the  phenomena  themselves,  it  is  of  no  value.  For  ex- 
ample, "  Land  may  rise  from  and  above  the  river  bed ;  then 
there  will  be  two  slopes  within  the  two  slopes  which  form  the 
river  basin,  and,  consequently,  there  will  be  two  lines  which 
bound  the  two  slopes  that  rise  above  the  river  bed."  It  is 
hardly  worth  while  to  go  roundabout  so  far  in  order  to  say  that 
rivers  may  include  islands  between  their  banks  !  An  excess  of 
logical  demonstration  of  elementary  matters  will  not  infre- 
quently leave  the  teacher  behind  the  class.  Children  do  not 
care  much  for  argument,  but  prefer  acquisition,  and  are  willing 
enough  to  accept  anything  within  reason.  Vivid  description 
and  appropriate  explanations  need  no  enforcement  by  a  con- 
structed and  visibly  logical  method. 

Be  careful  of  hasty  generalizations.  While  the  smaller  con- 
tinents possess  simple  slopes  from  their  mountain  axes  to  the 
sea,  the  largest  of  the  land  areas  contains  so  great  an  interior 
basin  that  it  should  not  be  overlooked  even  in  the  most  ele- 
mentary presentation  of  continental  form.  Do  not  jump  too 
rapidly  to  conclusions.  It  is  not  safe  to  say,  "  The  lack  of  long 
and  broad  slopes  is  the  plain  reason  why  Africa  remains  for 
the  greater  part  in  barbarism."  Do  not  over-emphasize  trifles. 
Leave  to  rival  book  agents  the  trivial  dispute  about  the  par- 
ticular lakelet  in  which  the  Mississippi  rises.  The  general  plan 
of  a  book  is  a  thousand  times  more  important  than  its  citation 
of  the  latest  census  reports.  Grasp  and  teach  the  spirit,  not 
the  letter. 

I  shall  add  but  a  few  paragraphs  on  geographical  errors. 
Most  of  these  are  found  in  the  divisions  of  geography  that  are 
concerned  with  explanation  of  phenomena;  that  is,  in  meteor- 
ology and  oceanography.  In  these  subjects  the  text-books  are 
nearly  always  behind  the  times. 

The  subject  of  tides  is  too  difficult  to  introduce  into  early 
teaching  except  in  a  descriptive  way.  The  usual  account  of  the 


THE  TEACHING  OF  GEOGRAPHY  103 

tide  opposite  the  moon  is  nearly  always  defective.  A  case  may 
be  quoted  in  which  an  author  rather  incredulously  says,  "  There 
is  a  great  pulsation  of  the  entire  ocean,  called  the  tides,  which 
is  supposed  to  be  the  yielding  of  the  water  of  the  globe  to  the 
attraction  of  the  moon  on  the  side  nearest  the  moon,  and  the 
holding  back  of  the  land  from  the  water,  on  the  side  farthest 
from  the  moon"  ;  and  then  adds  naively  in  a  footnote,  "This 
explanation  has  never  seemed  quite  clear  to  me  in  presenting  it 
to  children,  and  it  seems  to  me  possible  that  science  has  not  yet 
fully  explained  the  tides."  If  the  explanation,  as  given,  really 
represented  the  present  state  of  scientific  investigation,  the 
footnote  would  be  well  justified.  It  is  useless  to  attempt  to 
explain  the  tides  without  at  least  an  elementary  knowledge  of 
mechanics.  They  may  be  described  and  good  reasons  discovered 
for  referring  their  rise  and  fall  to  the  joint  action  of  the  moon 
and  sun ;  but  their  explanation  had  better  be  omitted  than 
travestied. 

The  winds  are  seldom  adequately  treated  in  the  ordinary 
text-books.  It  is  generally  said  that  the  air  around  the  equator 
is  heated  and  rises ;  then  the  colder  air  on  either  side  rushes  in 
to  fill  the  vacuum  thus  formed.  This  is  as  if  one  should  say  a 
lever  rises  under  a  weight  to  fill  the  vacuum  caused  by  the 
ascent  of  the  weight.  The  general  circulation  of  the  atmosphere 
is  referred  to  the  differences  of  temperature  between  the  equator 
and  poles ;  and,  on  this  basis,  a  tyro  in  physics  will  predict  the 
occurrence  of  low  pressure  around  the  equator  and  high  pressure 
about  the  poles ;  yet  in  the  charts  of  atmospheric  pressure  often 
introduced  into  the  recent  books  on  physical  geography,  the 
pressure  around  the  poles  is  found  to  be  low  and  not  high.  Any 
independent  pupil  would  be  justified  in  rejecting  a  theory  which 
was  apparently  so  soon  discountenanced  by  the  facts. 

Rain  is  nearly  always  wrongly  explained.  It  is  referred  to 
the  mixture  of  two  masses  of  air,  both  saturated  with  vapor,  but 
of  unlike  temperatures,  —  an  inadequate  and  extremely  unlikely 
process ;  or  it  is  referred  to  the  cooling  of  ascending  currents  of 
warm  lower  moist  air  by  the  cold  of  the  upper  regions,  or  by 
the  cold  of  the  mountains  on  their  path ;  but  the  main  cause  — 
the  spontaneous  cooling  by  expansion  of  ascending  currents  —  is 


104 


EDUCATIONAL  ESSAYS 


either  half-mentioned  or  altogether  omitted.  The  easy  belief  in 
the  artificial  production  of  rainfall  by  explosions  naturally  follows 
from  the  imperfect  teaching  of  this  subject. 

The  influence  of  the  earth's  rotation  on  the  course  of  the 
winds,  the  ocean  currents,  and  rivers  is  hardly  ever  properly 
presented.  There  is  always  either  the  implication  or  the  direct 
assertion  .that  bodies  moving  east  or  west  are  not  deflected  from 
their  course,  and  that  the  turning  to  the  right  or  left,  in  one 
hemisphere  or  the  other,  is  found  only  in  motions  along  the 
meridian.  This  is  all  wrong.  The  deflective  effect  of  the  earth's 
rotation  is  independent  of  the  direction  of  motion.  It  is  as  great 
on  a  motion  to  the  east  or  west  as  to  the  north  or  south.  It  is 
least  near  the  equator,  where  it  is  generally  referred  to ;  and 
greatest  near  the  poles,  where  its  action  is  seldom  mentioned. 
The  usual  reference  to  the  lagging  of  the  trade  winds,  as  they 
move  toward  the  equator  and  reach  latitudes  of  faster  eastward 
rotation,  would,  if  logically  carried  out,  warrant  the  belief  that 
friction  with  the  earth's  surface  prevents  the  lagging  of  the 
winds,  and  that  their  oblique  course  must  be  accounted  for  inde- 
pendently of  the  earth's  rotation.  The  reader  may,  if  he  wishes, 
see  the  disastrous  consequences  of  this  argument  in  Laughton's 
"  Physical  Geography  of  the  Winds  and  Currents,"  an  English 
work  of  good  standing,  but  one  in  which  this  particular  subject  is 
topsy-turvy. 

How  shall  the  earnest  teacher  avoid  such  errors  and  super- 
fluities as  I  have  mentioned  ?  There  is  only  one  way,  and  that 
is,  to  study  and  think  untiringly.  It  is  indeed  unfortunate  that 
a  simpler  prescription  cannot  be  given  to  overcome  the  difficulty 
that  many  a  teacher  would  gladly  be  rid  of.  Something  will  be 
done  by  the  introduction  of  better  and  better  text-books  and 
works  of  reference ;  more  will  be  done  if  school  boards  can  be 
prevailed  upon  to  give  teachers  sufficient  leisure  to  consider 
and  plan  out  their  heavy  tasks.  But  the  burden  of  the  work  of 
improvement  lies  with  the  teachers  themselves. 


THE  EXTENSION  OF  PHYSICAL  GEOGRAPHY 
IN  ELEMENTARY  TEACHING 

The  attempt  is  made  in  the  elementary  teaching  of  geography 
to  give  the  pupil  some  idea  of  the  form  of  various  land  areas. 
The  chief  means  of  accomplishing  this  large  task  are  ordinarily 
found  in  a  brief  chapter  treating  of  descriptive  or  of  physical 
geography,  and  introducing  certain  terms,  such  as  plain,  plateau, 
mountain,  valley,  river,  bay,  cape,  and  so  on.  Various  land  areas 
are  afterwards  described  in  accordance  with  this  terminology. 

It  is  my  contention  that  the  definitions  of  the  terms  thus 
introduced  are  not,  as  a  rule,  well  founded  on  a  clear  compre- 
hension of  the  essential  principles  of  physical  geography,  and 
that  in  too  many  cases  they  have  little  to  do  with  physical  geog- 
raphy, being  simply  descriptive,  and  not  physical  at  all.  To 
make  this  clear  I  shall  illustrate  what  seems  to  me  the  impor- 
tant difference  between  these  divisions  of  the  subject. 

Descriptive  geography  attempts  to  characterize  the  infinitely 
varied  forms  of  the  land  in  an  absolute  manner,  without  refer- 
ence to  their  origin,  and  with  little  consideration  of  their  natural 
relations.  A  canon  is  simply  a  narrow  valley,  not  a  young 
valley.  It  is  represented  as  differing  from  other  valleys  simply 
in  width,  not  in  age.  A  valley  is  a  depression  of  greater  or  less 
width  between  adjacent  higher  masses  ;  its  origin,  by  deforma- 
tion of  the  earth's  crust,  or  by  the  destructive  agencies  of  the 
weather,  is  often  omitted  as  if  irrelevant,  or  as  if  it  should  not 
be  mentioned  because  the  subject  in  hand  is  not  called  geology. 
A  bay  is  an  indentation  of  the  coast  line ;  its  production  by  the 
drowning  of  a  valley  is  unmentioned. 

Physical  geography  attempts  to  arrange  the  forms  of  the  land 
in  a  natural  order,  dependent  on  their  evolution  under  the  com- 
bined action  of  internal  constructive  forces  and  external  destruc- 
tive forces.  The  canon  of  the  Colorado  is  then  represented  not 

105 


106  EDUCATIONAL  ESSAYS 

simply  as  a  deep  and  narrow  valley ;  it  is  narrow  because  it  is 
still  so  young  that  it  has  not  yet  had  time  to  grow  wider ;  it  is 
deep  because  of  its  precocious  development,  resulting  from  the 
great  height  of  the  plateaus  in  which  it  is  incised.  The  valley 
of  California  is  taken  as  the  type  of  a  large  valley  of  deforma- 
tion, produced  by  the  uplifting  of  mountains  on  either  side  ;  the 
valley  of  the  Hudson,  or  of  the  Ohio,  might  be  presented  as 
the  type  of  a  valley  of  erosion,  both  of  these  being  wider  than 
the  canon  of  the  Colorado  because  they  are  older,  and  less  deep 
because  the  land  in  which  they  are  eroded  is  not  so  high  as  the 
plateaus  of  Arizona.  Certain  irregularities  of  the  seacoast  are 
rationally  referred  to  the  effects  of  the  submergence  of  an  eroded 
land  area ;  thus  Delaware  and  Chesapeake  bays,  Albemarle  and 
Pamlico  sounds,  are  simply  named  "  drowned  valleys,"  a  phrase- 
ology that  any  child  may  understand  ;  rivers  like  the  Hudson, 
having  large  volume,  although  fed  by  a  small  drainage  area,  are 
called  "  drowned  rivers,"  because  their  volume  is  dependent  on 
their  submersion  beneath  sea  level. 

Descriptive  geography,  or  that  which  ordinarily  passes  for  the 
physical  geography  of  the  land,  lags  far  behind  the  present  state 
of  knowledge  of  land  sculpture.  The  understanding  of  the  fea- 
tures of  the  land  surface  has  advanced  wonderfully  in  the  last 
half  century,  even  in  the  last  quarter  century ;  but  the  texts, 
in  most  cases,  seem  as  if  they  were  written  on  the  basis  of  an 
earlier  and  much  less  extended  knowledge.  They  are  extremely 
timid  regarding  the  destructive  work  of  the  weather.  They  are 
sadly  incomplete  regarding  the  manifold  products  of  glacial 
action.  They  are  deficient  concerning  the  meaning  of  the  varied 
forms  of  the  seacoast.  I  believe  that  the  chief  reason  of  these 
various  shortcomings  is  to  be  found  in  the  want  of  a  practical 
knowledge  of  field  geology  and  field  geography  on  the  part  of 
the  authors  of  text-books.  No  worthy  knowledge  of  physical 
geography  can  be  gained  without  such  a  preparation.  The  time 
is  past  when  it  is  admissible  to  describe  the  surface  of  the  land 
independently  of  the  structure  beneath  the  surface  and  without 
regard  to  the  forces  that  have  attacked  the  structure,  reducing 
it  by  greater  or  less  amounts  from  what  it  was  originally  towards 
what  it  will  be  ultimately.  A  description  of  the  land  that  is 


EXTENSION   OF  PHYSICAL  GEOGRAPHY 


107 


inattentive  to  these  manifest  and  natural  processes  of  evolution 
is  in  the  highest  degree  arbitrary  and  antiquated. 

The  rational  understanding  of  the  features  of  the  land  surface 
can  be  advanced  only  by  the  introduction  of  some  natural  sys- 
tem of  description  of  land  forms,  based  on  the  natural  processes 
of  their  evolution.  I  shall  refe'r  here  only  to  the  system  which 
seems  to  me  most  satisfactory.  This  begins  by  classifying  all 
regions  according  to  the  geological  structure  on  which  their 
initial  form  depends ;  it  then  sub-classifies  them  according  to 
the  degree  of  advance  that  has  been  made  by  the  destructive 
processes  of  erosion  in  reducing  the  initial  form  to  its  ultimate 
extinction  in  a  lowland  of  denudation.  I  shall  not  delay  here  to 
consider  the  complications  that  follow  from  the  interruption  of 
one  cycle  of  destructive  work  before  its  completion  by  the  intro- 
duction of  a  new  constructive  process  ;  all  this  may  be  logically 
included  in  the  fully  expanded  statement  of  the  system.  It  will 
be  sufficient  now  to  illustrate  its  application  by  a  few  simple 
examples.  But  before  doing  this  we  must  recognize  carefully 
the  different  positions  taken  by  the  pupil  and  the  teacher  with 
regard  to  the  subject. 

The  aim  of  the  entire  undertaking  must  be  kept  in  mind.  It 
is  to  give  our  school  children  so  clear  an  idea  of  the  more  com- 
mon forms  of  the  land  that  they  may  appreciate  them  when 
reading  or  when  traveling  about  over  the  country,  thereby  gain- 
ing a  better  understanding  of  history,  past  and  present.  For 
this  purpose  a  series  of  selected  and  emphatic  examples  should 
be  presented,  fully  illustrated  by  diagram  or  model.  The  variety 
of  illustration  cannot  be  great,  but  it  should  be  sufficient  to 
enforce  an  understanding  of  young  and  old  forms,  of  elevated 
and  depressed  coast  lines,  of  normal  and  accidental  events  in 
river  history,  and  so  on.  Each  of  these  examples  should  be 
enforced  by  the  selection  of  some  particular  region  which  serves 
as  its  type.  The  prominence  given  to  one  or  another  division  of 
the  subject  may  depend  largely  on  the  opportunity  afforded  by 
the  surroundings  of  the  school.  The  whole  world  cannot  be 
covered,  but  a  clear  understanding  may  be  given  of  features 
which  have  a  world-wide  distribution,  and  whose  more  especial 
occurrence  may,  if  desired,  be  made  the  subject  of  later  study. 


108  EDUCATIONAL  ESSAYS 

But  in  the  selection  and  presentation  of  examples,  it  is  essential 
that  they  should  follow  in  a  natural  order,  and  that  the  teacher 
should  be  acquainted  with  the  system  of  nature  to  which  they 
all  belong. 

A  parallel  may  be  drawn  with  the  teaching  of  botany.  A 
class,  at  the  beginning  of  this  "subject,  is  taught  a  variety  of 
terms  in  giving  names  to  the  various  parts  of  plants ;  preferably 
from  the  plants  themselves,  or,  in  lack  of  that,  from  good  draw- 
ings. The  terms  thus  taught  are  selected  from  a  much  larger 
number  familiar  to  the  expert  botanist ;  taken  all  together,  they 
have  a  rational  bearing  on  the  natural  relationships  by  which 
different  kinds  of  plants  are  classified,  and  by  which  their 
processes  of  growth  are  explained.  The  simpler  processes  of 
growth  are  considered  in  early  teaching,  and  the  genetic  re- 
lation of  various  parts  is  thus  brought  to  light.  The  essential 
point  here  is  that  the  introductory  teaching  of  botany  should  be 
guided  by  an  understanding  of  the  whole  subject  on  the  part  of 
the  teacher,  and  not  simply  by  a  verbal  knowledge  of  the  ele- 
ments that  the  scholars  are  to  learn,  or  by  a  knowledge,  how- 
ever extended,  of  the  medicinal  or  agricultural  uses  of  plants. 
Geography,  on  the  other  hand,  is  too  often  taught  as  if  it  were 
an  entirely  separate  subject  from  geology,  and  not  merely  a  sub- 
division of  the  study  of  the  earth  as  a  whole.  It  is  a  misfortune 
that  we  have  no  English  word  to  include  both  geography  and 
geology,  which  naturally  belong  together.  It  might  then  be 
easier  to  insure  a  general  knowledge  of  the  whole  science  on 
the  part  of  the  teacher,  even  if  his  scholars  were  to  learn  only 
the  rudiments  of  one  of  its  divisions. 

The  teacher  of  elementary  botany  must  know  something  more 
than  he  is  expected  to  teach.  He  must  be  reasonably  familiar 
with  the  more  difficult  orders,  of  which  little  mention  need  be 
made  in  elementary  classes,  as  well  as  with  the  simpler  orders 
from  which  nearly  all  elementary  illustrations  are  drawn.  He 
must  know  something  of  the  more  obscure  processes  of  growth 
concerning  which  a  class  of  beginners  can  learn  little,  as  well  as 
of  the  more  manifest  processes  which  every  child  may  observe. 
Otherwise,  the  teacher  would  not  be  qualified  in  the  modern 
sense  of  qualification. 


EXTENSION   OF  PHYSICAL  GEOGRAPHY  109 

The  teacher  of  elementary  geography  should,  in  like  manner, 
be  familiar  with  the  general  system  of  classification  of  land  forms, 
and  the  fundamental  principles  of  geology  on  which  the  classi- 
fication is  based,  as  well  as  with  the  larger  natural  and  political 
divisions  of  the  world,  their  physical  features,  inhabitants,  and 
so  on ;  and  the  fundamental  principles  of  geology  here  referred 
to  should  have  been  learned  in  the  field,  not  in  the  class  room ; 
otherwise,  they  are  as  artificial  as  the  knowledge  of  botany  that 
comes  only  from  books.  The  information  of  the  teacher  must 
go  beyond  that  expected  of  the  scholar  in  order  to  make  his 
teaching  safe  and  sound.  Teachers  sometimes  claim  to  teach 
more  than  they  know  ;  but  I  have  never  heard  this  claim  quoted 
with  satisfaction  by  the  teachers'  pupils.  With  this  explanation 
I  may  now  return  to  my  theme,  and  illustrate  what  is  meant  by 
a  natural  system  of  physical  geography,  indicating  at  the  same 
time  something  of  the  difference  of  knowledge  expected  of 
teacher  and  scholar. 

Mountains  early  claim  a  scholar's  attention.  They  may  have 
had  abundant  narrative  and  descriptive  illustration  in  the  earlier 
classes  of  the  grammar  schools.  The  Alps  may  be  taken  as  ex- 
amples of  vigorous  mountain  forms,  important  alike  from  their 
height  and  from  the  frequent  mention  of  them  that  the  scholar 
will  afterwards  meet  in  history,  if  not  in  travel.  Later  classes 
come  to  the  more  physical  consideration  of  mountains ;  and 
besides  the  many  interesting  matters  concerning  climate,  fauna, 
flora,  resources,  occupations,  and  other  factors  controlled  by 
their  form  and  altitude,  questions  will  arise  as  to  the  relations 
of  lofty  mountain  ranges  to  other  parts  of  the  earth.  The  first 
basis  of  correlation  is  found  in  the  mountain  structure.  Moun- 
tains are  prevailingly  regions  of  crushing  and  elevation  by  con- 
structional processes,  whereby  the  rocks  of  the  earth's  crust 
are  given  a  disordered  attitude.  For  a  time  after  the  mountain 
making,  much  of  the  form  and  height  due  to  the  constructional 
processes  of  growth  are  preserved ;  but  this  is  only  temporary, 
and  for  the  rest  of  the  mountain's  life,  form  varies  and  height 
decreases  from  their  initial  values.  Hence  while  all  regions  of 
crushed  and  disordered  structure  may  be  included  under  the 
general  class  of  mountain  regions,  the  maintenance  of  mountain 


HO  EDUCATIONAL  ESSAYS 

height  is  a  transient  characteristic  ;  mountains  are  lofty  while 
young,  but  from  that  time  on,  unless  rejuvenated  by  renewed 
processes  of  crushing  or  uplifting,  they  are  worn  down  lower 
and  lower,  and  finally  only  the  lowland  stumps  of  the  original 
mountains  remain.  From  the  time  of  youth  when  massive  con- 
structional forms  reared  their  summits  to  the  clouds,  to  the  time 
of  maturity  when  the  processes  of  sculpture  have  added  variety 
to  the  simpler  forms  of  early  construction,  and  to  the  time  of 
old  age  when  denudation  has  reduced  the  region  to  a  lowland 
surface  of  faint  relief,  there  is  a  simple  and  systematic  change 
of  form.  Unless  renewed  uplifts  intervene  to  restore  the  alti- 
tude lost  by  erosion  and  thus  delay  the  final  consummation 
(and  this,  by  the  way,  seems  to  have  been  a  common  exception 
to  the  simpler  rule),  there  is  no  permanence  in  mountains.  How- 
ever permanent  they  may  be  in  matters  relating  to  human  his- 
tory, the  real  physical  relation  of  mountains  cannot  be  perceived 
without  studying  mountain  history.  Their  growth,  their  wasting 
away,  and  their  final  extinction  must  be  recognized.  The  chief 
postulates  on  which  this  statement  rests  are  simply  that  the 
earth's  crust  suffers  deformations  ;  that  destructive  processes 
will  attack  surfaces  which  arise  above  the  hydrosphere  into  the 
atmosphere ;  and  that  time  is  long.  These  postulates  are  all 
extremely  safe. 

I  believe  that  all  this  general  matter  should  be  clearly  in  the 
mind  of  the  teacher.  How  far  he  may  pass  it  on  to  his  scholars 
will  depend  on  many  things.  He  must  consider  their  mental 
quality ;  not  simply  their  standing  in  school,  but  their  associa- 
tions out  of  school,  on  which  the  success  of  teaching  so  largely 
depends.  He  must  examine  the  opportunity  for  local  illustra- 
tion of  relevant  facts,  such  as  the  tilting  and  disorder  of  rock 
structure ;  abundant  illustrations  of  disorder  may  be  found  all 
along  our  Appalachians ;  but  in  the  Central  states  the  rocks  are 
not  only  generally  covered  over  by  loose  materials,  but  when 
seen  their  strata  lie  horizontal.  His  advance  will  depend  in 
part  on  the  supply  of  diagrams  and  models,  and  more  on  his 
ingenuity  in  making  them ;  but  more  than  all,  it  will  depend  on 
his  own  familiarity  with  the  facts  of  the  case  and  his  boldness 
in  presenting  them,  whether  mentioned  in  the  text-book  or  not. 


EXTENSION   OF   PHYSICAL  GEOGRAPHY  m 

I  believe  that  a  teacher  who  has  made  a  vacation  excursion,  on 
foot,  if  possible,  across  the  mountains  of  Pennsylvania,  and  thus 
come  to  an  appreciation  of  their  extraordinary  structure,  as 
deciphered  by  the  geologists  of  that  state ;  who  has  extended 
the  knowledge  thus  gained  by  a  general  study  from  books  and 
maps  of  other  mountain  structures  ;  who  has  in  some  way  or 
other  found  or  made  a  series  of  illustrations  by  which  the  facts 
that  he  wishes  to  refer  to  may  be  illustrated  to  his  classes,  and 
who  has  the  good  fortune  to  have  classes  of  intelligent  and  well- 
taught  scholars,  —  such  a  teacher  will  successfully  present  the 
problems  here  considered,  with  satisfaction  and  instruction  to 
his  pupils. 

If  the  extinction  of  mountains  by  denudation,  or  by  "  base- 
leveling,"  as  the  word  goes  among  geologists,  were  simply  an 
ideal  supposition,  without  actual  occurrence ;  if  its  occurrence 
were  known  only  in  the  remote  regions  of  the  world  and  did 
not  concern  our  home  geography,  we  might  have  little  regard 
for  it ;  its  place  would  be  better  taken  by  something  of  local 
value.  But  fortunately  for  the  variety  of  geographical  teaching, 
the  base-leveling  of  mountains  is  not  an  uncommon  or  remote 
fact.  We  here  in  New  England  live  on  an  old  base-leveled  moun- 
tain region.  Our  rock  structures  are  crushed  to  a  degree  that 
finds  a  close  parallel  in  the  structures  of  lofty  mountain  ranges. 
It  is  only  a-n  indolent  conservatism  that  fails  to  recognize  the 
former  existence  here  of  a  mountain  range  of  great  height,  per- 
haps as  high  as  the  Alps  of  to-day ;  and  therefore  as  closely 
comparable  with  the  Alps  as  the  decaying  trunk  of  a  prostrate 
oak  is  comparable  with  a  vigorous  shoot  from  an  acorn.  They 
do  not  look  alike,  yet  the  Alps  show  us  the  past  of  New  England, 
just  as  New  England  discloses  the  future  of  the  Alps. 

Climb  to  the  top  of  any  hill  in  central  Massachusetts  and 
notice  the  remarkable  accordance  of  height  among  all  the  sur 
rounding  hills.  They  unite  in  a  sky  line  of  extraordinary  sim- 
plicity. Look  at  their  rocks,  and  recognize  everywhere  the  signs 
of  great  disturbance  and  deep  erosion.  How  can  a  disturbed 
and  deeply  eroded  region  possess  a  generally  accordant  upland 
surface  unless  that  surface  is  the  base-level  down  to  which  all 
the  superincumbent  mass  has  been  reduced  by  denudation !  It 


112  EDUCATIONAL  ESSAYS 

need  not  be  imagined  that  the  old  mountains  were  absolutely 
worn  out,  and  that  a  geometrical  plane  was  produced.  A  low- 
land of  gentle  relief,  an  almost  plain  surface,  a  "peneplain," 
with  here  and  there  remnant  hills  and  mountains  rising  some- 
what above  its  softly  rolling  surface,  gives  a  fairer  picture  of 
the  form  to  which  mountain  ranges  fade  in  their  old  age. 

No  proper  appreciation  of  our  local  geography  can  be  gained 
until  the  observer  has  perceived  this  dominating  upland  surface, 
above  which  our  Wachusetts  and  Monadnocks  ascend  five  hun- 
dred or  a  thousand  feet,  and  beneath  which  our  present  valleys 
sink  by  a  similar  measure.  No  one  who  believes  that  physical 
geography  extends  beyond  the  limits  of  descriptive  geography 
towards  an  understanding  of  the  natural  relations  of  land  forms 
will  be  satisfied  with  the  recognition  of  this  old  peneplain  as  an 
unexplained  fact.  The  meaning  of  the  fact  is  reasonably  desired  ; 
fortunately  its  meaning  already  comes  within  the  limits  of  our 
high-school  teaching,  and  in  the  next  generation,  or  sooner,  I 
think  it  may  be  extended  downward  into  the  grammar  schools. 

It  is  not  intended  to  present  here  a  full  account  of  the  system 
of  physical  geography  adopted  in  my  college  teaching,  nor  to 
give  a  full  statement  of  the  physical  features  of  southern  New 
England.  A  significant  characteristic  of  this  region  is  selected 
to  illustrate  the  adopted  system,  which  I  have  considered  more 
fully  on  other  occasions,  and  which  can  be  touched  on  only 
lightly  in  a  brief  essay.  Indeed,  I  trust  that  the  reader  has 
perceived  a  certain  discrepancy  between  the  conditions  im- 
plied in  the  explanation  of  the  upland  of  southern  New  England 
as  an  old  base-leveled  mountain  region  and  the  considerable 
altitude  at  which  the  greater  part  of  it  now  stands  above  sea 
level.  An  old  mountain  region,  reduced  by  the  processes  of 
denudation  to  a  lowland  of  moderate  relief,  should  stand  close 
to  sea  level,  and  the  streams  should  be  powerless  to  sink  valleys 
beneath  its  general  surface.  Residual  mountain  stumps  might 
rise  moderately  above  it,  but  valleys  should  not  sink  below  it. 
The  present  altitude  of  our  New  England  plateau  and  its  dis- 
section by  valleys,  some  of  which  are  more  than  a  thousand  feet 
deep  below  the  plateau  upland,  must  therefore  be  taken  to  prove 
that  since  the  base-leveling  of  the  region  it  has  suffered  a  gentle 


EXTENSION  OF  PHYSICAL  GEOGRAPHY  1 1 3 

uplifting,  whereby  all  its  old  rivers  were  given  a  new  lease  of 
life  and  their  activities  again  quickened  ;  and  in  accordance  with 
this  opportunity  they  have  all  set  to  work  to  reduce  the  region 
to  the  present  base-level,  but  they  have  not  as  yet  advanced  far 
in  this  task.  The  valleys  are  well  begun,  but  the  greater  part 
of  the  plateau  mass  still  remains  to  be  consumed. 

If  one  travels  inland  west  from  Massachusetts  bay  or  north 
from  Long  Island  sound,  the  upland  surface  of  the  plateau  will 
be  found  to  ascend  gently,  from  sea  level  at  the  coast  line  to  an 
elevation  of  sixteen  hundred  feet  or  more  in  northwestern  Mas- 
sachusetts, and  even  higher  farther  north.  The  uplifting  of  the 
old  base-leveled  lowland  must  therefore  have  been  accomplished 
by  a  slight  tilting ;  the  part  that  we  now  live  on  rose  above 
its  former  level,  but  another  part  sank,  and  is  now  under  the 
Atlantic,  —  the  two  parts  forming  a  single  inclined  plane. 

The  largest  valley  that  has  been  excavated  in  the  uplifted 
portion  of  the  old  lowland  is  that  of  the  Connecticut,  because 
its  course  follows  a  belt  of  relatively  weak  red  sandstone  across 
Massachusetts  and  Connecticut  almost  to  the  sea.  This  valley 
indeed  deserves  the  name  of  a  lowland  of  the  second  order,  for 
its  surface  is  generally  of  moderate  relief,  near  present  sea  level, 
and  it  stands  distinctly  below  the  uplands  of  the  plateau  of 
harder  crystalline  rocks  to  the  east  and  west.  But  at  several 
points  in  the  valley  lowland  we  find  ridges  of  hard  volcanic  rock 
that  have  withstood  the  erosion  under  which  the  red  sandstones 
have  wasted  away ;  such  are  Mounts  Tom  and  Holyoke  in 
Massachusetts,  and  the  Hanging  Hills  of  Connecticut.  These 
are  residual  mountains  with  respect  to  the  surrounding  valley 
lowland,  just  as  Monadnock  and  Wachusett  are  residual  moun- 
tains with  respect  to  the  upland  plateau.  Monadnock  and  Mount 
Tom  are  both  residual  mountains,  but  they  belong  to  different 
generations  of  development ;  to  different  cycles  of  geographical 
evolution. 

I  have  introduced  this  latter  point  as  an  illustration  of  the 
more  detailed  knowledge  that  I  should  hope  the  New  England 
teacher  would  possess,  but  which  might  be  omitted  from  his 
teaching;  and  yet  I  have  hopes  that,  within  a  half  century, 
precisely  such  facts  as  these  will  be  the  subject  of  ordinary 


114  EDUCATIONAL   ESSAYS 

instruction.  Reference  has  already  been  made  to  the  down- 
ward extension  of  high-school  subjects  into  the  future  grammar 
schools.  Such  is  the  usual  course  of  events.  Microscopes  were 
once  the  treasures  of  the  few  learned  men ;  now  they  are  famil- 
iarly employed  in  any  ordinary  school-teaching  of  botany  or 
zoology.  The  isolation  of  oxygen  was  enough  to  make  a  chem- 
ist famous  a  hundred  years  ago ;  now  it  may  be  isolated  in  any 
school  laboratory.  The  distances  of  astronomy  and  the  remote 
ages  of  geology  were  obstinately  denied  by  all  but  the  most 
learned  of  earlier  generations  ;  now  they  are  taught  to  our  chil- 
dren, or  if  they  are  not,  we  regard  the  school  from  which  they 
are  excluded  as  misplaced  in  this  end  of  the  century.  Modern 
scientific  education  above  the  primary  grades  includes  subjects 
known  for  the  greater  part  only  to  the  few  a  short  time  ago. 
We  need  not  doubt  that  the  teaching  of  geography  will  be 
benefited  by  the  introduction  of  newly  discovered  facts,  just  as 
the  teaching  of  other  subjects  has  been.  Let  us  not  hold  back 
from  this  advance,  but  press  forward  to  it.  When  our  school- 
masters learn  the  modern  developments  of  physical  geography 
as  they  have  learned  those  of  botany  and  zoology,  when  our 
schools  have  geographical  laboratories  as  well  provided  as  are 
the  laboratories  of  physics  and  chemistry  in  the  best  schools  of 
to-day,  then  the  extension  which  we  are  now  urging  will  be  the 
commonplace  fact  of  public  education. 


VI 

GEOGRAPHY  IN  GRAMMAR  AND  PRIMARY 
SCHOOLS 

Geography  is  essentially  a  grammar-school  study.  It  should 
be  preceded  in  the  primary  school  by  such  simple  and  local 
observations  as  the  teacher  there  may  have  opportunity  to 
introduce,  and  by  descriptions  of  places  in  simple  reading  exer- 
cises ;  it  should  be  followed  in  the  later  years  of  the  grammar 
school  and  in  the  high  school  by  history,  for  the  extension  of 
descriptive  political  geography,  and  in  the  high  school  by  mod- 
ernized physical  geography,  or  physiography  as  some  would  call 
it,  for  the  fuller  explanation  of  natural  geography.  But  general 
descriptive  geography  should  be  well  acquired  during  the  very 
acquisitive  years  of  the  grammar-school  course. 

If  there  is  one  thing  more  important  than  another  in  the 
teaching  of  geography  in  the  grammar  schools,  it  is  that  the 
facts  of  the  subject  be  made  vivid  and  real.  Every  means  of 
the  teacher's  art  should  be  employed  to  secure  this  end.  Trav- 
elers who  have  seen  much  of  the  world  can  readily  make  a 
mental  picture  of  an  unseen  region  by  reading  a  good  descrip- 
tion of  it ;  but  children  in  our  schools  have,  as  a  rule,  only  the 
vaguest  impressions  concerning  the  places  whose  names  they 
recite.  How  can  it  be  otherwise  when  they  generally  have  only 
the  smallest  experience  with  the  world,  and  when  the  facts  are 
presented  to  them  in  the  briefest  language  in  text-books  that 
have  been  impoverished  by  compressing  all  their  descriptions 
into  short  paragraphs  for  recitation  ?  Let  the  teacher,  there- 
fore, strive  to  infuse  some  life  and  reality  into  the  subject  and 
bring  it  up  nearer  to  the  level  of  the  scholar's  intelligence. 
When  the  class  is  learning  the  succession  of  low  headlands 
along  our  Atlantic  coast,  for  example,  let  the  teacher  insert 
some  little  account  of  the  manner  in  which  the  capes  would 
appear  one  after  another,  if  seen  from  a  coasting  vessel,  each 

"5 


Il6  EDUCATIONAL   ESSAYS 

one  guarded  by  a  lighthouse  at  its  extremity,  or  by  a  light- 
ship on  the  shoals  offshore,  with  broad  recessions  of  the  coast 
between  them.  When  telling  of  smaller  streams  branching  from 
a  trunk  river,  stop  a  little  to  describe  how  the  valleys  of  the 
tributaries  join  the  main  valleys  ;  explain  the  importance  of  such 
points  for  early  settlements  and  modern  cities. 

The  class  need  not  remember  a  word  of  this  additional  matter  ; 
it  is  introduced  only  to  expand  the  explanation  and  to  maintain 
attention  on  the  subject  of  the  brief  text,  thus  making  it  more 
real  and  more  easily  remembered.  If  the  teacher  finds  difficulty 
in  supplying  explanatory  narrative  of  this  kind  —  that  is,  if  her 
knowledge  of  the  subject  is  but  little  greater  than  that  which  the 
class  attains  by  reading  the  barren  text,  let  her  lessen  the  empha- 
sis allotted  to  the  subject,  or  let  her,  as  soon  as  possible,  increase 
her  familiarity  with  it.  Recitations  of  the  mechanical  kind  make 
no  progress  in  correcting  the  fundamental  weakness  of  unreality 
in  the  study  of  geography.  Examinations  seldom  detect  it,  be- 
cause they  are  so  largely  occupied  with  questions  of  mere  locality. 
Let  us  consider  how  a  teacher  may  successfully  labor  to  over- 
come this  difficulty. 

I  believe  that  the  first  step  is  made  in  the  desired  advance 
when  geography  is  taught,  as  our  best  teachers  now  teach  it,  as 
if  it  were  a  thing  that  live  people  talk  about  out  of  doors  in  the 
real  world,  and  not  as  if  it  were  merely  the  contents  of  a  text- 
book that  is  closed  when  the  scholars  go  home.  Let  the  intro- 
duction of  geographical  topics  in  the  primary  schools  be  well 
correlated  with  the  grade  of  work  that  is  to  be  taken  up  in  the 
grammar  schools.  Let  the  beginning  of  the  study  in  the  grammar 
schools  be  made  by  a  somewhat  more'  advanced  quality  of  local 
observation,  illustration,  and  narrative  than  the  primary  scholars 
could  reach,  until  the  listening  and  watching  children  perceive 
that  they  are  learning  more  about  a  subject  whose  acquaintance 
they  first  made  even  before  their  earliest  school  days,  when  they 
began  to  walk  alone.  Teachers  in  the  country  especially  should 
encourage  excursions  on  half-holidays.  /  Let  there  be  a  healthy 
rivalry  developed  among  the  children  in  learning  the  features  of 
the  surrounding  district,  its  hills  and  valleys,  its  ledges  and 
meadows,  its  ponds  and  streams,  forests  and  fields ;  let  the 


GEOGRAPHY  IN  THE  SCHOOLS  117 

divides  between  the  streams  be  explored,  and  the  descent  of 
the  slopes  followed  down  to  the  brooks.  Every  element  of  form 
that  is  thus  seen  and  reported  by  the  children  in  school  may  be 
matched  by  the  teacher  with  its  larger  fellows  in  the  greater 
world,  of  which  the  class  is  now  to  learn  something.  This  is 
geography ;  and  such  an  introduction  to  it  is  far  better  than  a 
recitation  to  order  from  the  first  page  of  a  book.  Excursions 
are  more  difficult  in  cities  ;  but  they  are  not  impossible,  as  many 
enterprising  teachers  can  testify.  Some  children  in  every  class 
may  at  least  afford  a  little  journey  into  the  country  on  an  elec- 
tric car,  or  a  short  voyage  across  a  river  or  harbor  on  a  ferry- 
boat ;  and  the  things  that  these  children  see,  when  naturally 
talked  about  afterwards  in  school,  gain  a  greater  reality  to  the 
other  children  than  the  formal  homilies  of  the  first  paragraphs 
in  a  book. 

Turn  the  drift  of  the  ideas  obtained  by  excursion  and  narratives 
towards  the  first  chapter  of  the  text-book  that  is  employed.  En- 
large upon  the  theme  of  this  chapter  before  the  book  is  called 
for.  Then  open  the  book,  and  use  it  as  a  condensed  abstract  of 
the  subject  whose  beginnings  are  already  clearly  in  mind  on  a 
foundation  of  familiar  facts. 

By  some  such  device,  maintained  throughout  the  course  but 
varying  with  every  teacher,  the  paragraphs  of  the  book  will  take 
their  proper  place  as  the  summary,  not  as  the  substance  of  the 
subject.  Thus  employed,  any  text-book  is  better  than  none  ;  but 
when  the  "  teaching  "  is  all  done  by  recitations,  it  might  almost 
be  said  that  no  text-book  is  better  than  any.  The  barrenness  of 
blank  recitations  from  the  books,  and  the  vagueness  of  narratives, 
readings,  and  unwritten  object  lessons  without  a  book,  are  both 
dangers  that  are  avoided  by  the  use  of  both  methods.  Recita- 
tions give  precision  after  the  subject  has  become  real  by  illustra- 
tions of  various  kinds.  When  the  class  advances  rapidly  and 
there  is  a  little  time  to  spare,  expand  the  account  of  the  subject 
then  in  hand.  When  time  presses,  the  text  may  be  followed  more 
closely ;  its  brevity  is  then  properly  understood  as  only  the 
shorter  statement  of  what  would  be  pleasanter  if  it  were  longer. 

Now  the  fundamental  requirement  for  such  work  as  this,  in 
which  the  text-book  is  subordinated  to  the  teacher,  is  a  teacher 


Il8  EDUCATIONAL  ESSAYS 

with  an  easy  geographical  mind  ;  not  one  who  is  timid  when  out 
of  sight  of  the  text,  but  a  teacher  whose  familiarity  with  the  facts 
of  geography  requires  her  continually  to  restrain  the  plentiful 
description,  narrative,  or  anecdote  with  which  almost  every  para- 
graph of  the  page  might  be  illuminated.  It  will  be  only  after 
years  of  effort  that  a  teacher,  under  the  manifold  burdens  of 
grammar-school  work,  can  acquire  such  familiarity  with  geo- 
graphical facts.  The  normal-school  training  that  is  accepted  as 
fitting  high-school  graduates  for  grammar-school  teaching  is  only 
a  step  towards  the  desired  end,  and  sometimes  only  a  short  step. 
A  longer  step  will  be  taken  when  the  work  is  better  done  in  these 
preparatory  years,  but  no  preparation  that  our  younger  teachers 
can  bring  to  their  work  will  excuse  them  from  years  of  arduous 
study  while  teaching.  The  need  of  attaining  an  easy  mind  on 
several  subjects  besides  geography  at  the  same  time  is  the  most 
serious  difficulty  in  the  younger  teacher's  path  ;  and  this  difficulty 
must  greatly  embarrass  our  intermediate  schools,  until  a  practical 
method  is  invented  by  which  there  shall  be  a  teacher  for  each 
subject  instead  of  a  teacher  for  each  class. 

The  difficulties  in  the  way  of  becoming  experts  in  grammar- 
school  subjects  are  truly  formidable,  but  there  is  a  way  in  which 
great  assistance  can  be  given  in  overcoming  the  difficulties.  This 
is  in  teachers'  meetings.  It  is  disappointing  to  learn  how  seldom 
such  meetings  are  held.  The  more  thoughtful  superintendents 
and  principals  advocate  them.  Conscientious  teachers  approve 
of  them.  Where  they  have  been  carefully  tried,  they  are  found 
so  useful  that  they  cannot  be  given  up.  If  teachers'  meetings 
can  be  had  in  no  other  way,  it  would  be  better  for  the  scholars 
to  have  an  extra  half -holiday  every  fortnight,  so  that  the  teachers 
might  have  a  spare  afternoon  for  conferences,  with  suggestion 
and  discussion  in  small  parties.  Then  let  it  be  understood  that 
study  in  the  high,  normal,  and  training  schools  is  only  the  begin- 
ning of  the  teacher's  studious  career.  Let  the  mental  activity  of 
the  individual  teacher,  as  shown  to  her  principal  in  the  meet- 
ings, be  recognized  as  one  of  the  important  tests  of  fitness  for 
continued  appointment.  Give  all  subjects  a  due  share  of  time  in 
succession,  geography  along  with  the  rest;  each  subject  being 
continued  through  a  number  of  meetings,  perhaps  for  half  a  year. 


GEOGRAPHY  IN  THE  SCHOOLS  119 

At  nearly  every  meeting  let  every  teacher  contribute  an  item, 
an  abstract,  a  narrative ;  a  list  of  illustrations  of  one  subject  or 
another,  found  by  a  search  through  the  files  of  some  of  our  more 
accessible  magazines  ;  a  method  of  explaining  or  introducing  cer- 
tain of  the  more  troublesome  matters,  such  as  longitude,  map 
scales,  weather  maps.  In  cities  where  as  many  as  ten  or  twenty 
teachers  can  attend  a  fortnightly  meeting,  these  specific  contribu- 
tions of  matters  of  fact  or  method  cannot  fail  to  aid  many  another 
member.  Avoid  generalized  lectures  by  outside  experts  ;  at  least, 
do  not  let  these  take  the  place  of  the  regular  teachers'  meetings. 
The  essential  to  be  gained  comes  only  through  the  effort  of  the 
teachers  themselves.  But  this  is  a  theme  that  is  larger  than  my 
whole  subject,  and  I  cannot  pursue  it  further.  It  is  plain  that 
the  training  that  a  young  woman  may  have  before  she  begins  to 
teach  is  only  the  beginning  of  her  preparation  for  teaching ;  it 
serves  to  recommend  her  as  a  candidate  who  may  be  tried  as  a 
teacher;  but  real  fitness  is  not  to  be  expected  in  the  beginner. 
Nor  will  real  fitness  be  gained  merely  by  years  of  teaching ;  it 
comes  only  from  years  of  study  while  teaching.  Nothing  less 
than  unceasing  effort  will  develop  the  easy  mind  ;  and  of  all  aids 
in  this  effort,  I  believe  the  teachers'  meeting  to  be  the  best. 

It  is  a  sorry  device  to  substitute  methods  of  teaching  for 
knowledge  of  fact.  It  is  of  little  avail  for  the  poorly  prepared 
teacher  to  trust  to  psychological  principles.  Indeed,  from  what 
I  have  seen  of  it,  I  believe  that  many  teachers  are  as  much 
harmed  as  helped  by  an  effort  to  teach  in  accordance  with  a 
determined  order  of  mental  development  in  children.  This  ab- 
sorbingly interesting  matter  of  mental  development  is  a  difficult 
subject.  It  is  much  more  difficult  than  imparting  the  simple 
facts  of  •  descriptive  geography.  It  is  a  fine  subject  for  deep 
study,  but  it  is  a  dangerous  subject  for  the  inexperienced  to 
trifle  with.  A  clear  knowledge  of  the  facts  to  be  taught  and 
a  sympathetic  perception  of  the  difficulties  of  the  class  will  be 
of  greater  value  to  a  teacher  in  a  grammar  school  than  the 
scheme  of  mental  growth.  The  larger  pedagogical  principles 
too  often  tend  to  obstruct  a  teacher's  progress  in  the  simple 
studious  acquisition  of  a  subject.  All  serious  students  and 
teachers  of  pedagogy  of  course  agree  that  the  fundamental 


120  EDUCATIONAL  ESSAYS 

requirement  for  a  teacher's  success  is  knowledge.  This  is  so 
much  of  a  truism  and  so  easily  stated  that  it  seems  to  make 
less  impression  on  the  average  teacher  than  the  later  principles 
of  pedagogical  instruction,  which  are  concerned  with  the  mental 
processes  of  acquisition  and  memory.  The  fundamental  require- 
ment is  therefore  too  often  relatively  neglected,  apparently  with 
the  idea  that  a  general  understanding  by  the  teacher  of  the  way 
in  which  scholars  should  learn  will  take  the  place  of  the  nar- 
ratives, illustrations,  and  other  devices  that  I  have  here  referred 
to.  This  is  all  a  sad  mistake.  There  is  no  "  method  "  that  can 
replace  knowledge.  There  is  nothing  but  knowledge  that  will 
supply  the  teacher  with  a  means  of  awakening  and  holding 
attention  long  enough  upon  the  more  important  parts  of  a  sub- 
ject to  allow  them  to  sink  deeply  into  the  understanding.  iThe 
more  fully  the  teacher  is  possessed  of  her  subject,  the  less  will 
be  heard  of  terms  that  imply  a  conscious  analysis  of  mental 
processes ;  the  more  will  be  heard  of  the  subject  itself. 

Dr.  Rice,  in  one  of  his  instructive  articles  in  the  Forum 
some  years  ago,  gives  an  instance  of  too  much  consciousness 
of  process.  He  heard  a  grammar-school  teacher  ask  a  class, 
"With  how  many  senses  do  we  study  geography?"  And  the 
reply  was,  "  With  three  senses,  —  sight,  hearing,  touch."  Again, 
"How  many  senses  are  you  using  now?"  "Two  senses, — 
touch  and  hearing."  This  reminds  one  of  the  acquisition  that 
Moliere's  Jourdain  thought  he  had  made  when  he  learned  that 
he  had  all  his  life  been  talking  "prose."  Seeing  and  hearing 
are  as  natural  and  should  be  as  unconscious  as  breathing  to  a 
child  in  the  observant  grammar-school  years.  To  teach  that 
sight  is  used  in  studying  geography  merely  enlarges  the  "  morbid 
influence  of  consciousness."  It  has  no  useful  result.  -As  has 
been  well  said  of  manners,  so  we  may  say  of  the  senses  of 
perception  in  school  children,  "  conscious  study  would  tend  to 
distort  rather  than  to  fashion  them."  The  earnest  teacher  in 
the  grammar  schools,  whether  holding  classes  in  geography  or  in 
other  elementary  subjects,  may  safely  let  what  passes  with  many 
teachers  as  "  psychology  "  carefully  alone.  Talk  to  the  children 
in  school  as  simply  and  naturally  as  you  would  talk  to  them  out 
of  school.  Give  sincere  attention  to  the  presentation  of  the  facts 


GEOGRAPHY  IN  THE  SCHOOLS  121 

of  geography  in  a  simple  and  unaffected  manner ;  for  this,  as  a 
traveler  on  a  "  Sentimental  Journey"  once  said  of  a  much  more 
difficult  subject,  "  leaves  nature  for  your  mistress,  and  she 
fashions  it  to  her  mind."  Strive  to  be  quick  in  perceiving  the 
difficulties  that  the  scholars  meet ;  invent  many  devices  with 
which  to  avoid  or  lessen  these  difficulties ;  but  be  as  unconscious 
of  fixed  "  methods  "  as  the  children  are  of  their  eyes  and  ears. 

The  best  test  of  a  growing  reality  of  understanding  is  found 
in  the  increase  of  questions  from  the  class ;  not  questions  that 
show  a  puzzled  mind,  groping  for  an  understanding,  but  ques- 
tions that  ask  for  more  information,  or  that  display  a  healthy 
skepticism.  When  questions  arise,  a  teacher  distrustful  of  her- 
self takes  refuge  in  recitations ;  the  questions  are  promptly 
suppressed,  and  the  most  teachable  moments  of  the  class  are 
lost.  The  conscientious  teacher,  not  knowing  answers  to  the 
questions,  frankly  says  so  and  promises  to  find  out  about  them ; 
but  the  class  is  not  satisfied  if  the  teacher  has  to  postpone  her 
answers  too  often.  Jolly  little  boys  and  "peart"  little  girls  are 
then  naturally  enough  tempted  to  put  questions  just  for  the  fun 
of  "cornering"  the  teacher,  not  for  the  pleasure  of  learning 
more  for  themselves. 

Spontaneous  and  genuine  questions  are  only  an  encourage- 
ment to  an  experienced  teacher,  and  after  a  few  years  of  studious 
effort  there  will  not  be  too  many  hard  ones  whose  answers  have 
to  be  postponed.  When  occasional  hard  questions  come,  a  frank 
confession  of  ignorance  does  not  weaken  confidence,  and  a  hearty 
interest  in  the  novelty  of  the  question  may  even  strengthen  it. 
There  is  hardly  any  part  of  teaching  so  delightful  as  those  little 
excursions  from  the  regular  path,  prompted  by  appreciative  in- 
quiries from  growing  boys  and  girls.  Then,  if  ever,  a  teacher 
has  her  reward.  Then  the  real  nature  of  the  children  is  shown. 
Many  a  little  scholar  appears  "stupid"  when  trying  to  memorize 
his  paragraphic  text,  half  of  which  means  little  or  nothing  to  him; 
but  his  sufficient  ability  will  be  disclosed  if  the  subject  of  the 
text  is  naturally  talked  about  to  him,  not  in  brief  sentences  in  the 
style  of  the  book,  but  in  the  ordinary  style  of  simple  talk  with 
children.  His  replies  rather  than  his  recitations  may  be  taken 
as  a  measure  of  his  knowledge.  When  sufficient  comprehension 


122  EDUCATIONAL  ESSAYS 

is  gained  in  this  way,  recitation  from  the  text  is  useful  as  a 
means  of  securing  concise  and  definite  statement ;  but  if  time 
is  allowed,  the  verbatim  recitation  method  might  be  given  up 
altogether. 

It  is  only  in  the  easy  mind  of  the  well-informed  but  still 
studious  teacher  that  the  various  parts  of  a  subject  take  their 
proper  proportions  and  receive  their  proper  emphasis.  I  recall 
the  laborious  and  ill-proportioned  efforts  of  a  teacher  who  was 
following  a  recommendation  to  introduce  some  local  map  draw- 
ing in  an  early  stage  of  her  geography  class,  in  order  that  her 
scholars  should  afterwards  better  appreciate  maps  of  larger 
areas.  With  ill-judged  devotion  she  held  the  children  on  this 
relatively  trifling  matter  as  if  they  were  taking  a  course  in  sur- 
veying and  map  engraving.  Entirely  too  much  time  was  given 
to  the  work,  and  other  parts  of  the  subject  suffered.  The  draw- 
ing of  local  maps  should  be  treated  simply  as  a  device  by  which 
the  nature  of  a  map  is  made  clear.  It  cannot  be  expected  that 
the  untrained  hands  of  young  scholars  shall  do  more  than  make 
rough  outlines ;  and  the  more  clumsy  scholars  can  hardly  do 
this.  Yet  even  rough  outlines  will  aid  them  to  understand  that 
the  better-drawn  maps  in  their  text-book  are,  like  their  own  rude 
work,  representations  of  a  part  of  the  outdoor  world,  and  not 
merely  a  kind  of  colored  picture,  from  which  many  names  have 
to  be  learned.  In  every  school  there  may  be  some  scholars 
whose  maps  are  almost  worthless ;  they  should  not  be  too  much 
tormented  by  the  requirement  of  better  work  than  is  within 
their  reach ;  they  can  learn  a  useful  share  of  what  is  needed  by 
seeing  the  neater  maps  made  by  some  of  the  better  draftsmen 
in  the  class,  and  thus  vicariously  gain  their  experience. 

Too  much  emphasis  on  illustrative  work  of  this  kind  betrays 
the  inexperienced  teacher.  It  shows  that  she  needs  practice  in 
map  drawing  herself.  Let  her  utilize  the  opportunities  afforded 
by  summer  vacations  ;  let  her  reproduce  on  paper  the  route  that 
she  follows  on  some  short  trip  out  of  town  by  train  or  down  the 
river  by  boat,  taking  directions  by  compass  and  distances  by  time. 
Then  she  will  appreciate  that  drawing  a  map  from  observation  is 
not  a  very  easy  task.  Both  a  linear  and  a  fractional  scale  should 
be  added.  For  some  curious  reason,  the  question  of  map  scales 


GEOGRAPHY  IN  THE  SCHOOLS  123 

is  generally  but  half  understood.  I  have  seen  a  whole  roomful 
of  teachers  hesitate  —  to  say  the  least  —  when  asked  to  deter- 
mine for  themselves  the  scale  of  an  ordinary  terrestrial  globe. 
Certainly  their  minds  were  not  easy  on  this  point,  and  they  were 
not  ready  to  guide  their  scholars  over  it. 

The  proficiency  that  a  teacher  acquires  by  practice  in  map 
drawing  from  nature  will  be  of  great  assistance  in  class  work. 
A  few  lines  may  be  added  to  help  the  slower  scholars  ;  a  higher 
grade  of  accuracy  and  neatness  may  be  called  for  from  the  brighter 
scholars  ;  but  the  teacher's  own  knowledge  of  the  difficulties  of 
the  work  will  prevent  her  from  exacting  too  much  from  any  of 
the  young  beginners.  The  whole  affair  will  be  held  down  to  a 
grade  of  relatively  easy  accomplishment ;  and  thus  it  will  sub- 
side into  the  subordinate  position  that  it  deserves.  Map  drawing 
from  nature  is  a  device  that  should  never  be  omitted  from  the 
early  part  of  the  course,  but  it  should  not  be  carried  far.  At 
no  time  need  the  mere  copying  of  elaborate  maps  from  an  atlas 
be  allotted  as  a  lesson  in  geography  to  any  but  those  having 
a  natural  liking  for  drafting.  The  rest  of  the  class  can  better 
occupy  their  time  by  reading. 

The  teacher  who  has  an  easy  geographical  mind  will  be  fertile 
in  inventing  little  artifices  by  which  the  class  is,  all  unconsciously, 
carried  over  difficulties  of  understanding  that  block  the  path  of 
children  led  by  inexperienced  teachers.  Those  early  chapters  of 
many  text-books,  teeming  with  verbal  unrealities  about  mathe- 
matical geography,  are  only  so  many  stumbling-blocks  to  chil- 
dren under  teachers  who  have  never  gained  a  clear  mental  view 
of  the  rakish  attitude  of  the  whirling  earth,  as  it  marches  around 
the  sun.  The  figures  commonly  given  in  the  text  are  not  of 
much  value,  because  of  their  distortion  or  foreshortening,  and 
also  because  they  are  ready-made.  But  a  teacher  who  has  perse- 
vered through  an  elementary  astronomy,  who  has  watched  the 
changes  of  the  stars  with  the  advancing  seasons,  who  has  made 
for  herself  the  simple  little  models  or  diagrams  by  which  all  the 
necessary  astronomical  relations  of  the  earth  and  sun  may  be 
exhibited,  —  such  a  teacher  will  find  the  year,  the  seasons,  and 
the  varying  length  of  the  day  only  a  series  of  entertainments, 
well  adapted  for  gradual  presentation  to  her  class. 


124  EDUCATIONAL   ESSAYS 

It  is  a  mistake  to  think  that  the  greater  knowledge  of  such  a 
teacher  will  tempt  her  to  lead  her  classes  too  far  and  to  trouble 
them  with  unnecessary  difficulties.  It  is  true  that  her  classes  will 
advance  farther  than  those  led  by  a  teacher  who  is  puzzled  by 
the  facts  about  which  her  scholars  recite  in  unmeaning  words ; 
but  the  farther  advance  of  the  better-taught  scholars  will  be  made 
more  easily  than  the  apparent  advance  —  really  the  mystification 
—  of  the  others.  The  teacher  who  knows  much  of  the  subject, 
and  who  has  moreover  a  sympathetic  experience  with  school 
children,  will  wisely  select  the  essential  elements  from  her  abun- 
dant store  and  teach  them  easily ;  but  a  teacher  who  is  puzzled 
as  to  the  real  meaning  of  "  the  inclination  of  the  earth's  axis  to 
the  plane  of  its  orbit "  has  no  power  of  selection,  and  her  teach- 
ing is  heavy.  Unhappily  there  is  many  a  teacher  who  is  thus 
puzzled.  Recitation  from  the  text  is  her  only  refuge ;  the  chap- 
ter is  soon  passed  and  the  danger  is  over.  The  children,  how- 
ever, have  learned  very  little.  Better  omit  the  chapter  altogether, 
or  else  teach  it  clearly,  by  improvising  all  sorts  of  observations 
and  illustrations. 

One  of  the  most  interesting  items  of  early  geographical  study 
is  the  determination  by  observation  of  the  varying  noon  altitude 
of  the  sun.  A  great  difficulty  is  often  made  of  this  simple  matter. 
The  trouble  evidently  is  that  the  subject  is  really  not  clear  in 
the  minds  of  the  teachers.  And  yet  this  is  a  truly  eloquent 
subject  for  early  teaching.  In  a  well-arranged  course  of  primary- 
and  grammar-school  work  the  discovery  of  the  sun's  varying 
path  through  the  sky  should  come  before  the  class  meets  a 
statement  of  it  in  the  text-book.  The  approach  of  the  winter 
months  is  accompanied  by  a  loss  of  noon  altitude;  just  before 
the  Christmas  holidays  the  loss  becomes  very  slow  and  practi- 
cally ceases ;  and  on  returning  to  school  again  the  northward 
march  has  begun.  This  is  continued  almost  until  school  closes 
for  the  summer ;  but  the  full  height  of  the  June  solstice  may  be 
detected  before  vacation  begins.  The  greatest  and  least  angu- 
lar altitude  of  the  sun  may  be  determined  even  in  the  primary 
school,  if  desired  ;  and  from  these  two  quantities,  placed  on 
record  in  the  book  of  school  observations  kept  in  possession  of 
the  teacher,  the  scholars  may  in  later  years  easily  be  led  to 


GEOGRAPHY  IN  THE  SCHOOLS  125 

determine  for  themselves  the  inclination  of  the  earth's  axis,  the 
latitude  of  their  school,  and  all  the  limits  of  the  zones.  The 
advance  must  be  gradual,  but  it  is  very  easy.  The  extension 
of  observation  into  mathematical  geography  should  be  slow. 
Every  new  fact  should  be  allowed  to  rest  quietly  and  settle 
firmly  in  the  mind  before  another  is  added  to  take  the  atten- 
tion from  the  first.  But  there  can  be  no  doubt  that  all  this 
can  be  easily  introduced  into  grammar-school  teaching,  provided 
always  that  the  whole  problem  is  perfectly  clear  to  the  teacher, 
and  that  its  mention  does  not  in  the  least  disturb  her  ease 
of  mind. 

There  are  certain  profitable  devices  which  some  might  regard 
as  lacking  in  candor,  but  which  may,  I  believe,  be  properly  used 
in  order  to  secure  a  desired  sequence  in  the  presentations  of  the 
facts.  Suppose,  for  example,  that  a  class  of  young  children  has 
been  studying  the  continents  upon  a  globe,  as  their  first  study 
of  continents  should  always  be  made,  and  it  is  then  desired  to 
make  a  more  careful  examination  of  North  America  on  a  map 
of  a  larger  scale.  Place  a  wall  map,  rolled  up  on  its  stick,  in 
the  corner  of  the  room  before  the  school  opens.  Begin  the  les- 
son in  geography  with  the  globe,  and  ask  various  questions  about 
North  America,  leading  at  last  to  some  question,  such  as  the 
length  of  the  smallest  of  the  Great  Lakes,  which  cannot  be  deter- 
mined on  a  globe  of  ordinary  size.  Even  the  best  scholar  in  the 
class  will  be  at  a  loss  ;  and  if  the  proper  relations  are  established 
between  the  teacher  and  her  class,  the  embarrassment  of  the 
scholars  will  be  frankly  expressed.  Then  the  teacher  may  say, 
"  Sally,  bring  me  the  map  that  is  rolled  up  in  the  corner  of  the 
room  there.  Tom  and  Harry,  lift  that  table  alongside  of  this 
one,  so  that  we  can  spread  out  the  map  and  look  at  it."  Small 
divisions  of  the  class  may  then  in  turn  inspect  the  new  map, 
and  answer  questions  that  could  not  be  answered  from  the  globe. 
The  scale  of  the  map  may  be  determined,  and  compared  with 
that  of  the  globe.  As  on  the  globe,  so  on  the  map,  while  it  is 
still  lying  flat,  the  outward  course  of  the  larger  rivers  from  the 
continental  interior  may  be  noted  and  accepted  as  an  indication 
of  the  general  descent  of  the  land  from  the  central  part  towards 
the  surrounding  oceans. 


126  EDUCATIONAL  ESSAYS 

At  the  opening  of  the  next  lesson  in  geography,  the  map  of 
North  America  may  be  again  spread  on  the  table  and  a  map  of 
South  America  may  be  in  a  closet  near  at  hand.  South  America 
has  already  been  seen  on  the  globe.  Some  simple  comparison 
may  be  made  between  the  two  great  divisions  ;  for  example,  their 
western  mountains  and  their  three  great  eastern  rivers.  Then 
let  the  teacher  ask  the  big  boy  of  the  class  to  help  her  hang  the 
map  of  North  America  on  the  wall,  out  of  the  way ;  while  an- 
other scholar  is  sent  for  the  map  of  South  America,  which  takes 
its  turn  on  the  table.  The  object  of  these  harmless  subterfuges 
is  to  introduce  new  facts  and  illustrations  as  far  as  possible  only 
when  the  want  of  them  is  felt  by  at  least  some  members  of  the 
class.  This  is  a  much  more  natural  and  intelligent  method  of 
procedure  than  one  which  takes  up  a  new  subject  because  it  fol- 
lows the  last  one  on  the  page  of  a  book.  Moreover,  the  presen- 
tation of  the  wall  map  first  in  a  horizontal  position  on  a  table 
will  avoid  the  misunderstanding  that  teachers  sometimes  en- 
counter as  to  the  uphill  course  of  northward  flowing  rivers.  As 
the  Mackenzie  was  first  seen  running  out  from  the  continental 
center,  much  in  the  same  fashion  as  the  Mississippi,  there  will 
be  no  question  about  its  flowing  uphill  when  the  map  is  placed 
where  it  belongs  on  the  wall.  Again,  until  the  map  is  needed, 
it  is  out  of  place  in  the  schoolroom ;  as  much  out  of  place  as 
the  apparatus  for  the  later  part  of  a  course  in  physics  would  be 
on  the  lecture  desk  in  the  opening  lecture.  It  is  less  laborious 
for  the  teacher  to  place  the  maps  on  the  wall,  once  for  all ;  but 
it  is  monotonous  for  the  scholars  to  have  the  same  furnishings 
in  the  schoolroom  all  the  year. 

There  is  one  aspect  of  geographical  teaching  in  this  country 
that  is  not  generally  recognized.  Few  persons  suspect  that  the 
proper  teaching  of  geography  in  the  grammar  schools  is  greatly 
hampered  by  an  insufficient  investigation  and  a  prevailing  igno- 
rance of  the  facts  concerning  our  own  country.  I  do  not  mean 
ignorance  on  the  part  of  teachers,  but  an  absolute  ignorance 
that  cannot  be  removed  until  the  facts  are  investigated  by  trained 
observers  on  the  ground.  The  poverty  of  home  illustrations  is 
therefore  not  due  to  the  lack  of  natural  material,  but  to  the  gen- 
eral ignorance  concerning  the  abundant  material  that  undoubtedly 


GEOGRAPHY  IN  THE  SCHOOLS  127 

exists.  Consider  the  case  of  the  Empire  State.  In  the  first  place, 
there  is  no  respectable  map  of  its  area !  There  is  no  map  to 
which  the  teacher  can  turn  for  a  clear  picture  of  its  beauti- 
fully varied  features.  There  is  not  only  no  map ;  there  is  not 
even  a  good  written  description  of  its  surface  forms.  We  may 
of  course  find  various  accounts  of  the  state  in  encyclopedias  and 
gazetteers,  but  not  one  of  them  discloses  the  facts  in  the  light 
of  modern  geographical  science.  There  is  no  one  who  withholds 
the  facts.  No  one  has  yet  learned  them,  except  in  a  fragmentary 
way,  here  and  there.  The  same  is  more  or  less  true  of  nearly 
all  the  other  states.  Some  of  them  are  well  mapped,  but  not 
many.  None  of  them  are  adequately  explored  and  described 
geographically.  The  wealthy  states  of  New  York,  Pennsylvania, 
and  Ohio  are  about  as  poorly  off  in  this  respect  as  the  western 
territories. 

I  have  addressed  the  National  Geographic  Society  on  this 
subject,  and  suggested  that  the  geological  surveys  of  the  vari- 
ous states  should  be  asked  to  consider  the  feasibility  of  under- 
taking a  direct  geographical  study  of  their  territory,  and  reporting 
on  the  results  in  a  style  that  would  be  easily  understood  by  our 
common-school  teachers.  If  such  reports  were  made  in  succes- 
sive annual  chapters,  they  might  be  reprinted  in  the  reports  of 
the  state  boards  of  education  and  thus  placed  more  generally  in 
the  hands  of  teachers.  The  gradual  accumulation  of  good  mate- 
rial in  the  course  of  a  decade  would  furnish  a  highly  prized 
source  of  home  knowledge.  Text-books  would  be  refreshed  by 
the  incorporation  of  the  new  information.  Teachers  would  be 
greatly  aided  by  employing  it  as  a  basis  for  their  descriptions 
and  illustrations.  It  would  compete  with  teachers'  meetings  for 
a  chief  place  in  the  improvement  of  geographical  teaching.  I 
wish  that  superintendents  and  teachers  all  over  the  country 
would  join  me  in  the  movement  to  secure  this  result. 

Perhaps  the  impression  that  I  may  make  by  frequent  repeti- 
tion of  the  recommendation  that  the  teacher  must  study  unceas- 
ingly is  that  the  teacher's  life  ought  to  be  even  more  wearisome 
than  it  is  at  present.  It  must  certainly  be  laborious  if  it  is  to 
be  successful ;  but  the  consciousness  of  an  easy  geographical 
mind  is  a  good  return  for  all  the  labor  that  it  has  cost  to  gain 


128  EDUCATIONAL  ESSAYS 

it ;  and  surely  the  easy  mind  is  a  delightful  substitute  for  the 
anxiety  and  drudgery  of  teaching  a  half-known  subject.  Indeed, 
I  believe  there  is  nothing  that  will  so  surely  soften  the  hard 
lines  of  a  teacher's  life  as  the  freedom  from  thraldom  to  the 
text-book,  and  the  recreation  afforded  by  a  change  of  device  and 
illustration  from  time  to  time. 


VII 
PHYSICAL  GEOGRAPHY  IN  THE  HIGH  SCHOOL 

Limitation  of  the  Subject.  A  review  of  the  older  books  on 
physical  geography,  and  of  some  of  the  newer  books  also,  will 
show  that  their  various  authors  have  not  reached  a  clear  agree- 
ment as  to  the  limits  of  the  subject.  It  has  been  allowed  to  run 
over  upon  physics  and  astronomy  on  one  side  and  on  geology, 
botany,  and  zoology  on  the  other.  As  a  result  the  central  and 
truly  geographical  parts  of  the  subject  have  as  a  rule  been  com- 
pressed below  the  space  that  they  should  occupy  when  properly 
developed.  A  way  out  of  this  confusion  is  found  in  a  report 
recently  made  by  the  Committee  on  College  Entrance  Require- 
ments to  the  National  Educational  Association.  The  reporting 
members  of  the  sub-committee  concerned  with  our  science  unani- 
mously agree  that  "  it  should  be  the  aim  to  exclude  a  number 
of  subjects  frequently  treated  under  physical  geography,  but 
more  appropriately  included  under  other  heads ;  for  example, 
purely  astronomical  matter,  certain  principles  of  physics,  the 
classification  of  animals  and  plants,  and  tables  of  geological 
periods.  Important  and  interesting  as  these  subjects  are  in  their 
proper  connections,  it  is  believed  that  a  better  mental  discipline 
will  be  obtained  from  physical  geography  when  all  its  parts  are 
closely  joined  to  its  leading  theme,"  namely,  "  the  physical  en- 
vironment of  man,"  under  which  the  principal  headings  are  "  the 
earth  as  a  globe,"  "  the  atmosphere,"  "  the  oceans,"  and  "  the 
lands." 

The  agreement  upon  this  limitation  of  the  subject  by  the 
teachers  present  at  the  meeting  of  the  sub-committee,  and  the 
approval  of  their  agreement  indicated  by  the  publication  of  their 
report  by  the  National  Educational  Association,  mark  a  decided 
step  forward  from  the  indefiniteness  of  earlier  years.  Although 
slow  in  coming,  the  limitation  is  really  an  outgrowth  of  Ritter's 

129 


130  EDUCATIONAL  ESSAYS 

teaching  that  geography  is  the  study  of  the  earth  in  relation  to 
man,  from  which  one  may  naturally  deduce  the  definition  of 
physical  geography  —  or  physiography  —  as  the  study  of  those 
features  of  the  earth  which  are  involved  in  the  relation  of  earth 
and  man ;  that  is,  the  study  of  man's  physical  environment.  In 
later  years  of  education  the  physics  of  the  atmosphere,  the  forms 
of  the  land,  and  other  branches  of  the  subject  may  be  studied 
for  themselves  alone  under  the  general  name  of  terrestrial 
physics,  or  under  such  special  names  as  meteorology,  geomor- 
phology,  and  so  on,  without  special  regard  for  their  human  rela- 
tions ;  but  when  first  encountered  the  limitation  of  the  subject 
to  man's  physical  environment  has  the  great  advantage  of  hold- 
ing all  its  topics  close  to  their  most  important  and  interesting 
theme.  The  earth's  form  and  size,  its  rotation  and  revolution, 
are  geographical  as  well  as  astronomical  topics ;  but  a  list  of 
planets,  their  dimensions,  distances  from  the  sun,  and  periods 
of  rotation  and  revolutions  are  astronomical  topics.  Let  the 
teacher  introduce  these  interesting  items  if  her  interest  turns 
towards  astronomy,  and  if  time  can  be  spared  for  the  purpose ; 
but  the  space  that  they  would  occupy  in  the  text-book  should 
be  saved  for  the  fuller  presentation  of  strictly  geographical 
topics.  To  illustrate  this  by  personal  experience,  I  may  note 
that  the  nebular  hypothesis  held  its  inherited  place  in  my  lec- 
tures only  so  long  as  the  richness  of  the  rest  of  the  subjects 
was  not  sufficiently  developed  to  crowd  out  so  irrelevant  an 
astronomical  theory. 

The  forms  -of  the  land  can  be  well  seen  only  through  the  eye 
of  the  understanding,  which  shows  them  to  be  the  product  of 
agencies  that  have  operated  for  long  periods  of  past  time ;  the 
"shut-in  "  valleys  of  the  St.  Francois  mountains  of  Missouri  and 
the  Baraboo  ridge  of  southern  Wisconsin  are  never  appreciated 
until  they  are  seen  as  involving  long  stretches  of  time  in  their 
preparation.  Thus  far  time  is  an  element  of  geographical  as 
well  as  of  geological  consideration ;  but  the  specific  subdivision 
of  past  time  into  periods  and  the  consideration  of  the  events 
that  occurred  during  those  periods  in  their  historical  order  is 
purely  geological.  By  all  means  let  the  inventive  teacher  bring 
in  abundant  and  helpful  illustrations  from  all  pertinent  fields 


PHYSICAL  GEOGRAPHY  IN  THE   HIGH  SCHOOL     131 

of  knowledge,  but  let  the  teacher  also  recognize  that  there  is 
a  well-defined  theme  in  physical  geography  whose  logical  devel- 
opment must  govern  the  selection  of  topics  that  really  constitute 
the  framework  of  the  course.  A  fact  may  be  interesting  and 
important,  but  it  must  also  be  pertinent  to  our  science  if  a  place 
is  to  be  given  to  it  in  a  well-organized  text-book  of  physical 
geography. 

Geographical  Evolution.  The  contrast  between  older  and 
newer  methods  of  treatment  is  as  well  marked  as  between  the 
older  and  newer  limitations  of  our  subject.  In  the  days  of  Ritter 
many  subdivisions  of  physical  geography,  and  especially  the 
chapters  devoted  to  the  forms  of  the  lands,  were  treated  empir- 
ically, because  no  adequate  explanation  had  then  been  found  for 
them ;  and  the  relation  between  organic  forms  and  their  inor- 
ganic environment  was  explained,  when  explained  at  all,  by  the 
philosophy  of  teleology,  —  the  philosophy  which,  among  other 
things,  regards  the  earth  as  prepared  for  man,  —  because  no 
conception  had  then  been  gained  of  the  duration  of  the  past  time 
or  of  the  development  of  the  various  forms  of  life.  Since  those 
days  two  great  principles  have  been  discovered,  both  of  vast 
importance  to  geography.  One  is  the  evolution  of  land  forms, 
contributed  from  geology ;  the  other  is  the  evolution  of  living 
forms,  contributed  from  biology.  Great  advances  have  also  been 
made  in  the  physical  study  of  the  atmosphere  and  the  ocean. 
As  a  result  it  is  now  possible  to  treat  all  aspects  of  physical 
geography  in  a  rational  manner,  and  at  the  same  time  to  show 
the  fundamental  importance  of  the  relation  between  physical 
environment  and  life.  The  changes  thus  wrought  by  the  century 
are  revolutionary  in  physical  geography  as  well  as  elsewhere,  and 
it  is  incumbent  upon  us  to  see  that  our  pupils  reap  full  advantage 
from  the  new  opportunities  thus  broadly  opened  before  them. 

Causes  and  Consequences.  There  is  no  better  measure  of  the 
degree  of  modernization  in  the  treatment  of  physical  geography 
than  the  evenness  with  which  a  rational  or  explanatory  treat- 
ment is  applied  to  all  its  parts.  In  the  earlier  books,  explanation 
was  offered  only  for  the  more  active  phenomena,  such  as  winds, 
currents,  and  volcanoes ;  geographical  features  that  were  not 
evidently  the  result  of  active  processes  were  merely  described. 


132 


EDUCATIONAL  ESSAYS 


In  the  newer  books  the  attempt  is  made  to  extend  explanation 
uniformly  all  over  the  field  of  study.  A  review  of  older  and 
newer  methods  is  especially  interesting  in  regard  to  the  forms 
of  the  lands.  Sand  dunes,  for  example,  have  nearly  always  been 
mentioned  in  connection  with  their  simple  and  evident  origin 
by  wind  action ;  but  the  erosive  action  of  weather  and  water  in 
shaping  valleys  has  been  slowly  and  incompletely  introduced. 
Canons  have  been  given  too  much  importance,  and  only  the 
more  recent  books  have  instanced  wide-open  valleys  and  worn- 
down  mountains  as  illustrating  the  advanced  stage  of  destruc- 
tive development  in  which  canons  are  but  the  younger  stage. 
It  is  undoubtedly  true  that  many  items  of  the  subject  are  not 
yet  fully  explained,  but  there  are  many  others  for  which  good 
explanation  is  well  assured.  Let  the  latter  be  selected  to  form 
the  body  of  the  subject  in  elementary  teaching,  while  the  former 
are  left  aside  for  the  present,  or  given  at  most  only  a  subordi- 
nate place.  The  judicious  application  of  this  principle  will  not 
impoverish  the  subject  by  reducing  it  to  scanty  dimensions,  but 
will  enrich  it  by  the  addition  of  intelligent  explanations.  The 
pupils  will  from  the  outset  gain  the  habit  of  looking  at  the  sub- 
ject in  a  rational  way.  They  may  to  advantage  even  be  preju- 
diced with  the  opinion  that  all  its  parts  are  within  the  reach  of 
explanation ;  then,  if  an  unexplained  fact  is  encountered  later, 
it  will  be  attacked  vigorously  in  the  belief  that  explanation  can 
surely  be  found  by  persistent  study. 

Equally  significant  with  explanatory  treatment  is  the  applied 
treatment ;  that  is,  the  presentation  of  every  item  as  an  element 
of  the  environment  in  which  the  life  of  the  earth  has  been 
developed,  and  by  which  it  is  still  conditioned  at  every  turn. 
This  second  test  of  modernized  treatment  is  as  valuable  as  the 
first.  When  the  applied  treatment  of  the  subject  is  understood 
it  will  be  recognized  that  plants,  animals,  and  man  should  not 
be  given  special  chapters  for  themselves  in  the  modern  limita- 
tion of  the  contents  of  physical  geography,  for  the  very  suffi- 
cient reason  that  mention  of  them  is  distributed  all  through  the 
subject.  Gravity  determines  the  "  standing  "  position  of  plants 
and  animals.  Latitude  and  longitude  should  be  taught  as  devices 
by  which  man  takes  advantage  of  the  form  and  rotation  of  the 


PHYSICAL  GEOGRAPHY  IN  THE  HIGH  SCHOOL     133 

earth  to  determine  his  position  on  it,  not  as  abstract  mathemat- 
ical problems.  The  chapters  on 'temperature  and  moisture  give 
opportunity  for  mentioning  many  appropriate  consequences  as 
to  the  distribution  of  plants.  Under  the  description  of  the  shal- 
low border  of  the  oceans,  where  the  waters  lie  upon  the  so-called 
"  continental  shelf,"  proper  opportunity  is  found  for  referring  to 
these  waters  as  the  habitat  of  food  fishes  and  therefore  as  valu- 
able fishing  grounds.  A  general  account  of  the  larger  land  forms 
leads  up  to  the  control  exerted  by  continents,  mountains  (espe- 
cially the  Himalaya),  and  deserts  (especially  the  Sahara)  upon 
the  distribution  of  man  and  animals.  Under  "  mountains,"  ref- 
erence is  made  to  their  significance  as  refuges  for  conquered 
tribes  or  peoples.  Avalanches  and  landslides  are  not  finished 
with  a  description  and  explanation  of  inorganic  phenomena 
alone ;  they  are  also  presented  as  dangers  to  which  people  liv- 
ing in  mountain  valleys  are  subjected.  Here  we  may  well  intro- 
duce Guyot's  eloquent  sentence  as  a  practical  guide  in  our  work  : 
'•  To  describe  without  rising  to  the  causes  or  descending  to  the 
consequences  is  no  more  science  than  merely  and  simply  to 
relate  a  fact  of  which  one  has  been  a  witness."  The  phrase 
''causes  and  consequences"  thus  comes  to  serve  as  a  touch- 
stone by  which  both  the  explanatory  and  the  applied  treatment 
of  the  subject  may  be  easily  tested.  Just  as  a  topic  that  is 
beyond  explanation  had  better  as  a  rule  be  omitted,  in  order  to 
give  fuller  attention  to  topics  that  can  be  explained,  so  a  topic 
that  has  no  connection  with  the  manner  in  which  organic  forms 
are  distributed  or  with  the  occupations  in  which  men  are  engaged 
should  in  nearly  all  cases  be  excluded  as  of  less  importance  than 
those  topics  in  which  such  connection  is  manifested.  Neither 
test  of  the  touchstone  should  be  applied  rigidly  or  arbitrarily ; 
but  the  habit  of  looking  for  causes  and  consequences  is  a  most 
useful  aid  in  the  development  of  the  subject.  No  one  need  fear 
that  the  reasonable  application  of  this  test  will  deprive  physical 
geography  of  anything  that  rightly  belongs  to  it. 

The  omission  of  "  man,"  "  animals,"  and  "  plants  "  as  chapters 
in  physical  geography  frequently  causes  objection  on  the  part 
of  those  who  hold  to  the  older  plan  of  treatment.  Against 
such  objections  I  would  urge  the  following  considerations :  The 


134  EDUCATIONAL  ESSAYS 

necessity  for  the  study  of  man  comes  largely  because  the  treat- 
ment of  geography  proper  has  been  too  empirical  and  unintelli- 
gent ;  when  this  old  fashion  is  corrected  there  will  be  no  need 
of  a  chapter  on  man  in  physical  geography.  Plants  and  animals 
are  properly  subjects  for  zoology  and  botany ;  their  structural 
features  and  their  classification  cannot  be  taught  merely  as 
chapters  in  another  subject.  On  the  other  hand,  palms  and 
pines,  elephants  and  polar  bears,  may  be  freely  mentioned  in 
a  treatise  on  physical  geography  as  exhibiting  in  their  distri- 
bution the  effects  of  climatic  control ;  wheat  and  corn  fields 
are  appropriate  products  of  the  rich  soil  on  our  prairies,  in 
contrast  to  the  forests  which  grow  on  the  stony  soils  of  our 
Appalachian  mountains  and  uplands.  It  is  not  necessary  to 
have  studied  the  biological  relations  of  these  organic  forms 
in  order  to  make  intelligent  use  of  them  as  illustrations  of  the 
effect  of  environment.  But  the  actual  distribution  of,  useful 
plants  and  animals  is  strictly  a  geographical  subject,  and  no 
intelligent  or  effective  treatment  of  political  or  economic  geog- 
raphy can  be  reached  if  the  facts  of  distribution  are  omitted 
from  it. 

Physical  Geography  Abroad.  It  is  interesting  in  this  connec- 
tion to  glance  at  the  treatment  of  physical  geography  abroad,  in 
contrast  to  the  treatment  recommended  by  the  sub-committee  of 
the  National  Educational  Association.  As  to  limitation  of  con- 
tent there  is  the  same  wide  diversity  that  has  hitherto  existed 
here,  but  without  any  strong  movement  now  apparent  to  reduce 
the  subject  to  better  definition.  Absence  of  proper  limitation  is 
most  apparent  in  the  "physiography"  of  the  South  Kensington 
examinations  in  England,  where  the  subject  is  a  sort  of  exten- 
sion of  a  very  elementary  treatment  of  physical  geography.  It 
reaches  as  far  as  spectroscopic  observations  of  stars  and  nebulae, 
evidently  because  of  the  presence  of  an  astronomer  on  the  com- 
mittee in  charge  of  this  division  of  the  examinations ;  and  the 
physical  geography  of  the  lands  is  almost  lost  sight  of,  evidently 
because  no  physical  geographer  is  on  the  directing  committee. 
This  is  the  more  remarkable  and  regrettable  when  it  is  remem- 
bered that  the  term  "  physiography "  has  been  adopted  because 
of  Huxley's  use  of  it  as  a  title  for  a  series  of  lectures  in  1869 


PHYSICAL  GEOGRAPHY  IN  THE  HIGH  SCHOOL    135 

and  1870.  The  lectures  were  reduced  to  book  form  in  1878, 
and  in  the  preface  then  published  we  find  the  following  inter- 
esting statement : 

I  borrowed  the  title  of  "  physiography  "  as  I  wished  to  draw  a  clear  line 
of  demarcation,  both  as  to  matter  and  method,  between  it  and  what  is  com- 
monly understood  by  "physical  geography."  Many  highly  valuable  com- 
pendia of  physical  geography,  for  the  use  of  scientific  students  of  that 
subject,  are  extant ;  but,  in  my  judgment,  most  of  the  elementary  works  I 
have  seen  begin  at  the  wrong  end,  and  too  often  terminate  in  an  omnium- 
gatherum  of  scraps  of  all  sorts  of  undigested  and  unconnected  information, 
thereby  entirely  destroying  the  educational  value  of  that  study  which  Kant 
justly  termed  the  "  propaedeutic  of  natural  knowledge."  I  do  not  think  that 
a  description  of  the  earth,  which  commences  by  telling  a  child  that  it  is  an 
oblate  spheroid,  moving  round  the  sun  in  an  elliptical  orbit,  and  ends  with- 
out giving  him  the  slightest  hint  towards  understanding  the  ordnance  map 
of  his  own  county,  or  any  suggestion  as  to  the  meaning  of  the  phenomena 
offered  by  the  brook  which  runs  through  his  village,  or  the  gravel  pit  whence 
the  roads  are  mended,  is  calculated  either  to  interest  or  to  instruct.  And 
the  attempt  to  convey  scientific  conceptions,  without  the  appeal  to  observa- 
tion, which  can  alone  give  such  conceptions  firmness  and  reality,  appears  to 
me  to  be  in  direct  antagonism  to  the  fundamental  principles  of  scientific 
education.  "  Physiography  "  has  very  little  to  do  with  this  sort  of  "  physical 
geography."  My  hearers  were  not  troubled  with  much  about  latitudes  and 
longitudes,  the  heights  of  mountains,  depths  of  seas,  or  the  geographical 
distribution  of  kangaroos  and  Composite.  Neglecting  such  points  of  infor- 
mation—  of  the  importance  of  which,  in  their  proper  places,  I  entertain  no 
doubt  —  I  endeavored  to  give  them,  in  very  broad,  but,  I  hope,  accurate  out- 
lines, a  view  of  the  "  place  in  nature  "  of  a  particular  district  of  England,  the 
basin  of  the  Thames,  and  to  leave  upon  their  minds  the  impression  that 
the  muddy  waters  of  our  metropolitan  river,  the  hills  between  which  it  flows, 
the  breezes  which  blow  over  it,  are  not  isolated  phenomena,  to  be  taken  as 
understood  because  they  are  familiar.  On  the  contrary,  I  have  endeavored 
to  show  that  the  application  of  the  plainest  and  simplest  processes  of  reason- 
ing to  any  one  of  these  phenomena  suffices  to  show,  lying  behind  it,  a  cause, 
which  again  suggests  another,  until,  step  by  step,  conviction  dawns  upon 
the  learner  that  to  attain  to  even  an  elementary  conception  of  what  goes 
on  in  his  parish,  he  must  know  something  about  the  universe  ;  that  the 
pebble  he  kicks  aside  would  not  be  what  it  is  and  where  it  is  unless  a  par- 
ticular chapter  of  the  earth's  history,  finished  untold  ages  ago,  had  been 
exactly  what  it  was.  It  was  necessary  to  illustrate  my  method  by  a  con- 
crete case  ;  and  as  a  Londoner  addressing  Londoners,  I  selected  the  Thames 
and  its  basin  for  my  text.  But  any  intelligent  teacher  will  have  no  diffi- 
culty in  making  use  of  the  river  and  river  basin  of  the  district  in  which  his 
own  school  is  situated  for  the  same  purpose. 


136  EDUCATIONAL  ESSAYS 

It  is  said  that  much  disappointment  was  felt  by  those  inter- 
ested in  the  development  of  rational  methods  in  education,  on 
finding  that  teachers  in  various  parts  of  England  were  following 
Huxley  in  taking  as  their  text  the  Thames  instead  of  their  local 
river !  Still  greater  disappointment  may  be  felt  on  seeing  how 
far  the  spirit  of  what  Huxley  meant  by  the  name  "physiog- 
raphy "  is  lost  sight  of  in  the  books  that  undertake  to  present 
the  requirements  of  the  South  Kensington  examinations  on  that 
subject.  It  may,  I  believe,  be  fairly  claimed  that  the  recom- 
mendations of  the  conference  on  geography,  above  referred  to, 
much  more  nearly  represent  the  "sort  of  physical  geography" 
in  which  the  great  English  naturalist  was  interested  than  do  the 
outlines  issued  by  the  most  authoritative  board  of  examinations 
in  England  to-day. 

An  explanatory  treatment  is  usually  applied  in  German  and 
French  schoolbooks  to  the  active  phenomena  of  the  earth,  but 
the  treatment  is  not  uniformly  characteristic  of  all  parts  of  the 
subject.  Applied  treatment  is  almost  universally  lacking  in 
European  schoolbooks  on  physical  geography ;  and  when  en- 
countered it  seems  to  be  introduced  by  accident  rather  than 
as  the  result  of  a  systematic  plan.  Its  omission  is  especially 
characteristic  of  the  German  books,  whose  comprehensive  thor- 
oughness is  often  remarked,  but  whose  plan  would  place  them 
rather  under  the  heading  of  terrestrial  physics  than  under  phys- 
ical geography,  as  here  defined.  Hence  it  may  be  said  that 
when  the  recommendations  in  the  report  of  the  National  Edu- 
cational Association  reach  the  stage  of  general  and  practical 
application,  physical  geography  will  be  better  organized  in  this 
country  than  in  Europe, — a  result  that  may  be  placed  to  the 
credit  of  the  unofficial  educational  organizations  of  the  country, 
which  are  so  generally  influential  in  bringing  about  reforms,  and 
which  are  here  very  much  less  hampered  by  the  restrictions  of 
a  centralized  or  bureaucratic  control  of  educational  matters  than 
is  the  case  abroad. 

Let  us  now  turn  to  the  problem  of  the  arrangement  of  topics 
under  the  four  chief  headings  of  our  subject. 

Systematic  Treatment :  the  Atmosphere.  It  is  important  that 
a  careful  arrangement  as  well  as  a  judicious  selection  of  topics 


PHYSICAL  GEOGRAPHY  IN  THE  HIGH  SCHOOL    137 

should  be  made,  in  order  that  the  subject  should  advance  sys- 
tematically, in  as  logical  a  progress  as  actually  prevails  in  geom- 
etry or  Latin,  or  as  is  possible  in  botany  or  zoology.  Passing 
"  the  earth  as  a  globe"  for  lack  of  space,  an  example  of  the 
arrangement  may  be  given  under  the  heading  "  the  atmos- 
phere," by  which  the  correlation  of  the  prevailing  winds  and 
general  distribution  of  rainfall  may  be  impressively  presented. 
First  comes  the  general  circulation  as  determined  by  the  differ- 
ence of  temperature  prevailing  between  the  equator  and  poles, 
and  as  affected  by  the  eastward  rotation  of  the  globe.  Well- 
defined  consequences  as  to  the  distribution  of  pressure  and  the 
oblique  movements  of  the  upper  and  lower  currents  are  reason- 
ably deduced  from  accepted  physical  principles  governing  such 
movements,  but  the  difficulty  here  is  that  the  real  explanation 
of  the  winds  cannot  be  presented  in  an  elementary  fashion  ;  the 
problem  is  inherently  complicated,  and  only  the  more  important 
results  are  appropriate  for  high-school  pupils  ;  hence  the  gen- 
eral principle  that  cause  must  be  presented  with  fact  cannot 
here  be  fully  carried  out.  Difference  of  temperature  and  the 
rotation  of  the  earth  may  be  mentioned  as  the  chief  controls  of 
wind  movement  and  direction,  but  the  logical  connection  of 
cause  and  effect  cannot  be  fully  explained.  Nothing  need  be 
said  about  the  distribution  of  atmospheric  pressure  unless  the 
text  and  the  teacher  are  prepared  to  explain  the  low  pressures 
of  high  latitudes.  It  is  true  that  it  has  become  fashionable  in 
recent  years  to  copy  Buchan's  pressure  charts  in  elementary 
books,  but  it  would  be  more  philosophical  to  postpone  them  to 
more  advanced  study.  Variations  of  pressure  at  sea  level  are 
not  of  importance  as  factors  of  geographical  environment ;  and 
it  is  difficult  to  give  a  simple  explanation  of  the  observed  varia- 
tions. The  winds  determined  by  general  differences  of  equato- 
rial and  polar  temperatures  may  be  called  planetary,  because  such 
winds  are  to  be  expected  on  all  planetary  bodies,  and  the  chief 
members  of  the  planetary  circulation  may  be  described  along 
with  the  rainy  and  dry  belts  that  they  control.  The  second  step 
is  more  intelligible,  as  it  involves  the  effect  of  seasonal  changes 
of  temperature,  themselves  well  explained  by  the  changing 
declination  of  the  sun ;  relatively  simple  modifications  of  the 


138  EDUCATIONAL  ESSAYS 

planetary  wind  system  (and  of  its  rainy  and  dry  belts)  are  thus 
described,  to  which  the  name  terrestrial  winds  is  to  be  given. 
The  shifting  of  the  equatorial  calm  belts  and  the  associated  de- 
velopment of  monsoon  winds  and  sub-equatorial  rains  in  the 
summer  hemisphere  find  mention  at  this  stage ;  also  the  relaxa- 
tion of  the  westerly  winds  of  the  temperate  zone  of  the  summer 
hemisphere,  and  their  acceleration  in  the  temperate  zone  of  the 
winter  hemisphere,  with  the  correlated  migration  of  the  tropical 
calm  belt  and  the  associated  occurrence  of  the  winter  sub-trop- 
ical rains.  The  third  step  is  made  by  considering  the  irregular 
distribution  of  land  and  water,  from  which  it  appears  that  the 
systematic  development  of  the  terrestrial  winds  is  better  seen 
in  the  southern  hemisphere,  while  strong  modifications  of  winds 
and  rainfall  are  associated  with  the  great  alternations  of  land 
and  water  areas  of  the  northern  hemisphere.  It  may  be  fairly 
claimed  for  this  method  of  presentation  that  it  binds  together 
all  the  elements  of  the  problem  —  temperature,  pressure,  winds, 
and  rainfall  —  in  a  rational  association,  by  which  the  memory 
as  well  as  the  understanding  is  greatly  aided.  Nearly  all  the 
topics  introduced  under  "  the  atmosphere  "  may  be  appropriately 
attached  to  the  scheme  of  treatment  here  outlined  ;  and  all  may 
be  led  forward  to  important  consequences. 

The  Ocean.  Under  the  heading  "  the  ocean,"  the  sequence 
of  items  is  fairly  well  agreed  upon.  They  are  :  the  form  of  the 
ocean  basins  ;  the  composition  and  temperature  of  ocean  water  ; 
the  deposits  on  the  ocean  floor  ;  movements  in  the  form  of  waves, 
currents,  and  tides ;  influence  of  climate ;  and  control  over  dis- 
tribution of  organic  forms.  The  only  point  on  which  I  would 
lay  special  emphasis  here  is  that  tides  should  follow  waves  (with 
currents  between,  as  the  consequence  of  winds  and  temperatures), 
so  that  the  tidal  currents  may  be  explained  as  the  orbital  move- 
ments of  the  water  in  the  tidal  waves.  Under  tides,  a  good  ex- 
planation of  the  tide-making  forces  may  be  given  to  pupils  who 
have  studied  geometry  and  physics ;  otherwise,  it  is  hardly 
worth  while  to  attempt  explanation.  It  should  suffice  to  point 
out  that  the  tides  run  on  lunar  time,  and  hence  must  in  some 
way  be  associated  with  the  moon.  An  explanation  that  does  not 
explain  is  not  worth  its  time. 


PHYSICAL  GEOGRAPHY  IN  THE  HIGH  SCHOOL     139 

Activities  of  the  Lands.  Under  the  heading  "  the  lands  " 
there  is  as  yet  no  general  agreement  as  to  the  order  of  topics, 
or  indeed  as  to  the  topics  themselves.  After  various  experiments 
in  this  division  of  the  subject,  I  have  adopted  the  scheme  indi- 
cated in  the  following  statement.  A  general  account  of  the 
activities  or  habits  of  the  lands  opens  the  subject,  and  here  we 
find  the  best  warrant  for  the  previous  consideration  of  the  deep 
ocean  floors,  in  themselves  so  remote  from  relations  with  man, 
but  so  excellent  a  foil  for  the  presentation  of  the  real  character- 
istics of  the  lands.  The  sea  floors  are  cold  and  dull,  for  no  sun- 
light reaches  them,  though  they  may  have  some  illumination  from 
phosphorescent  animals,  as  is  indicated  by  the  eyes  and  the 
color  patterns  of  abyssal  fauna ;  their  oozy  deposits  are  almost 
as  monotonous  as  their  gently  undulating  form  ;  they  are  silent, 
and  without  change  of  weather  or  variety  of  climate.  The  lands 
are  alternately  light  and  dark,  warm  and  cold,  even  and  uneven, 
active  and  quiet,  noisy  and  silent ;  here  is  one  composition,  there 
is  another,  with  great  differences  of  weather  and  climate  in  time 
and  place,  and  the  surface  is  nearly  everywhere  wasted  and  fur- 
rowed by  valleys,  down  which  the  loss  of  the  land  is  carried  away 
by  rain-fed  streams  to  become  the  gain  of  the  sea.  Now  that  evo- 
lutionists as  well  as  poets  recognize  that  variety  is  the  very  spice 
of  life,  there  is  little  wonder  that  the  land  surface  and  not  the 
sea  floor  has  come  to  be  the  home  of  the  higher  animals,  higher 
in  organization,  in  instincts,  and  in  intelligence,  with  man  at 
their  head.  A  general  chapter  on  the  land  may  thus  be  made  of 
much  interest  and  value.  Special  emphasis  should  be  given  to  a 
brief  account  of  weathering  and  washing,  topics  of  great  impor- 
tance in  their  later  applications  :  the  systematic  relation  of  parts 
in  valley  systems  as  well  as  in  river  systems  deserves  much 
attention  as  a  general  characteristic  of  the  lands ;  but  it  is  not 
desirable  here  to  enter  into  details,  for  the  reason  that  the  closer 
knowledge  of  rivers  and  valleys  requires  a  previous  understand- 
ing of  the  initial  land  forms  on  which  the  rivers  have  worked 
and  in  which  the  valleys  are  carved.  As  at  present  advised,  I 
should  also  include  in  this  preliminary  chapter  some  brief  men- 
tion of  the  slow  movements  of  the  earth's  crust,  whereby  the 
outline  of  the  land  areas  is  slowly  varied  through  the  ages.  Here 


140  EDUCATIONAL  ESSAYS 

a  sea-floor  border  is  added  to  a  continent  by  a  movement  of  ele- 
vation ;  there  a  land  border  is  submerged  beneath  the  sea  by  a 
movement  of  depression.  It  is  true  that  these  statements  are 
empirically  introduced  in  this  connection,  and  that  no  explana- 
tion of  them  can  be  attempted,  for  the  cause  of  crustal  move- 
ment is  a  puzzle  even  to  the  advanced  student  of  geology.  The 
sufficient  reason  for  introducing  brief  mention  of  crustal  move- 
ment at  this  early  stage  is  that  examples  of  their  effects,  en- 
countered a  little  later,  may  be  then  understood  more  easily. 

Features  of  the  Lands.  The  lands  are  next  to  be  treated  in 
several  chapters.  Through  each  chapter  the  development  of 
the  land  forms  there  considered  should  be  treated  from  the 
point  of  view  of  geographical  evolution,  a  problem  too  large 
for  presentation  here.  In  recent  years  I  have  made  a  particular 
point  of  beginning  this  division  of  the  subject  with  the  chapter 
on  coastal  plains,  because  of  all  land  forms  they  are  most  easily 
apprehended  ;  that  is,  the  origin  of  young  coastal  plains,  the  posi- 
tion that  they  occupy  with  respect  to  their  surroundings,  the 
developmental  changes  produced  by  the  destructive  attack  of 
weather  and  water  can  all  be  readily  understood  by  young 
scholars  without  more  preliminary  study  than  is  given  in  the 
general  chapter  on  the  activities  of  the  lands.  The  great  advan- 
tage resulting  from  a  full  and  clear  understanding  of  the  first 
example  of  land  forms  is  that  a  serious. beginning  is  thus  made 
of  treating  land  forms  genetically  and  rationally.  Although  not 
usually  allowed  much  space,  coastal  plains,  modern  and  ancient, 
young,  mature,  and  old,  uplifted  and  depressed,  include  a  great 
variety  of  forms ;  the  reasonable  explanation  that  can  easily  be 
given  to  all  these  forms  affords  the  pupils  good  grounds  for 
the  expectation  that  plateaus,  mountains,  volcanoes,  and  other 
forms  in  the  following  chapters  may  be  no  less  rationally  treated. 
This  expectation  is  not  disappointed  in  the  chapter  on  plateaus, 
or  in  the  earlier  examples  that  may  be  given  of  simple  mountain 
forms ;  but  when  disordered  mountain  ranges  are  reached,  it 
is  not  desirable  to  attempt  an  explanatory  discussion  of  their 
greatly  deformed  structures,  or  of  all  their  complicated  forms. 
Fortunately,  the  pupil  will  not  complain  of  lack  of  material  if 
nothing  more  is  attempted  under  this  subdivision  of  the  chapter 


PHYSICAL  GEOGRAPHY  IN  THE  HIGH  SCHOOL     141 

than  the  description,  with  some  explanation,  of  peaks,  ridges, 
spurs,  passes,  ravines,  valleys,  and  slopes.  The  treatment  of 
subdued  and  worn-down  mountains  that  follow  young  and  vigor- 
ous mountains  is  much  simpler  and  may  be  readily  enough 
understood.  Worn-down  mountains,  now  uplifted  and  again  un- 
dergoing dissection,  include  examples  of  many  regions  whose 
description  and  explanatory  treatment  to-day  is  a  refreshing 
contrast  to  the  inattention  of  earlier  years. 

Volcanoes  form  a  chapter  that  may  naturally  follow  moun- 
tains ;  but  it  is  important  to  distribute  earthquakes  through 
both  these  chapters  in  order  to  remove  the  old  idea  that 
they  have  only  to  do  with  volcanic  action.  "  Volcanoes  and 
Earthquakes  "  as  a  chapter  heading  has  no  logical  place  unless 
it  is  paralleled  with  ''Mountains  and  Earthquakes"  as  another. 
Neither  heading  is  a  good  one ;  it  would  be  as  appropriate  to 
say  volcanoes  and  eruptions,  or  mountains  and  dislocations ;  for 
eruptions  and  earthquakes  are  both  subordinate  topics  under 
volcanoes,  as  dislocations  and  earthquakes  are  under  mountains. 
Furthermore,  earthquakes  are  associated  only  with  growing 
mountains  and  volcanoes,  and  not  with  the  old  stages  of  these 
forms ;  hence  the  permanent  association  with  either  land  form 
indicated  by  chapter  headings  is  inadmissible. 

Rivers  and  Valleys.  Under  all  the  topics  thus  far  mentioned, 
rivers  and  valleys  have  had  an  essential  place,  for  it  is  impossible 
to  treat  the  development  of  land  forms,  or  to  describe  existing 
forms  in  a  rational  manner,  without  constant  reference  to  the 
valleys  that  have  been  worn  in  them  and  to  the  rivers  by  which 
the  waste  is  washed  away  along  the  channel  in  the  valley  floor. 
From  the  very  first,  rivers  and  valleys  have  been  made  charac- 
teristic parts  of  the  land  surface ;  lakes  are  directly  associated 
with  rivers  because,  when  considered  in  their  true  light,  they 
are  but  "  ephemeral  phases  in  the  history  of  rivers."  Rivers 
and  lakes,  and  the  valleys  and  basins  they  occupy,  are  therefore 
considered  wherever  need  be  in  connection  with  plains,  plateaus, 
mountains,  and  volcanoes.  But  there  are  numerous  details  of 
interest  and  importance  that  deserve  special  consideration  un- 
der the  guidance  of  a  scheme  of  river  development ;  hence  a 
chapter  on  rivers  and  valleys  may  advisedly  follow  those  already 


142  EDUCATIONAL  ESSAYS 

mentioned,  reviewing  and  extending  what  has  already  been  pre- 
sented. The  development  of  meanders  and  cut-offs,  the  migra- 
tion of  divides  and  the  resulting  rearrangement  of  drainage 
systems  by  river  capture,  the  peculiar  features  of  valleys  whose 
streams  have  been  beheaded,  are  details  of  this  kind.  This  is  a 
strong  departure  from  the  English  method,  sanctioned  by  the 
South  Kensington  examinations,  as  at  present  planned,  of  plac- 
ing lakes  and  rivers  under  the  same  general  division  with  the 
oceans,  because  they  are  all  water :  a  method  that  cannot  be 
too  strongly  condemned  by  those  who  desire  to  see  a  reasonable 
treatment  of  physical  geography  introduced.  As  well  take  clouds 
and  rain  from  the  study  of  the  atmosphere  as  lakes  and  rivers 
from  the  study  of  the  lands. 

The  Waste  of  the  Land.  There  is  a  chapter  that  naturally 
follows  rivers  and  valleys  in  which  I  have  become  increasingly 
interested  during  the  past  ten  years  on  account  of  its  growing 
richness ;  the  more  it  is  considered  the  more  it  seems  to  con- 
tain. It  may  be  entitled,  "  The  Forms  assumed  by  the  Waste 
of  the  Land  on  the  Way  to  the  Sea."  Like  the  chapter  in 
which  rivers  are  especially  considered,  this  one  repeats  certain 
items  already  met  with  under  the  four  chapters  on  the  chief 
classes  of  land  forms ;  but  many  other  items  which  there  was 
then  no  sufficient  opportunity  to  describe  without  too  long  a 
delay  may  now  be  taken  up  deliberately.  The  process  of 
weathering,  whose  importance  is  so  great  that  it  was  presented 
as  an  essential  characteristic  of  the  lands,  is  now  reviewed,  thus 
leading  to  a  consideration  of  the  sheet  of  rock  waste  or  dis- 
crete, as  Gilbert  calls  it,  with  which  so  much  of  the  land  is 
covered,  and  more  particularly  to  an  examination  of  the  forms 
assumed  by  the  slow-moving  waste  as  it  creeps  and  washes 
down  the  slopes  to  the  valleys,  and  as  it  is  carried  along  by 
streams.  It  may  be  fairly  claimed  for  this  chapter  that  it  gives 
a  greatly  broadened  view  of  familiar  facts  and  presents  them  in 
their  true  relations.  We  are  all  familiar  with  the  forms  assumed 
by  the  waters  of  the  land  on  the  way  to  the  sea, —  springs,  brooks, 
rivers,  lakes,  and  falls ;  we  should  be  equally  familiar  with  the 
forms  assumed  by  the  waste  of  the  land  on  the  way  to  the  sea, 
—  talus  slopes,  alluvial  fans,  flood  plains,  deltas. 


PHYSICAL  GEOGRAPHY  IN  THE  HIGH  SCHOOL    143 

Climatic  Control  of  Land  Forms.  Thus  far  it  has  been  tacitly 
implied  that  the  development  of  land  forms  always  goes  on 
under  what  may  be  called  a  normal  climate ;  that  is,  a  climate 
in  which  the  precipitation,  chiefly  in  the  form  of  rain,  is  suffi- 
cient to  fill  all  basins  to  overflowing.  All  that  precedes  concern- 
ing land  forms  may  be  regarded  as  a  consideration  of  the 
control  of  land  forms  by  normal  climate.  Attention  must  now 
be  given  to  two  other  climates,  the  arid  and  the  glacial.  Wind 
in  one  case,  and  ice  in  the  other,  replaces  water  as  the  chief 
agent  of  transportation ;  and  peculiar  land  forms  are  developed 
under  these  peculiar  controls.  Here  are  placed  those  peculiar 
regions  known  as  interior  drainage  basins,  in  which  certain 
highly  specialized  correlations  of  form  and  process  are  found  ; 
correlations  that  are  very  little  understood  by  explorers,  if  one 
may  judge  by  the  unappreciative  method  of  description  often 
adopted.  Nothing  is  more  significant  of  advance  in  the  rational 
treatment  of  geography  than  the  recognition  lately  allowed  to 
forms  of  glacial  origin ;  and  it  is  truly  gratifying  to  find  that 
there  are  children  now  in  schools  who  know  a  drumlin  when 
they  see  it,  and  who  can  give  it  a  name  that  will  concisely  sug- 
gest the  meaning  desired  to  a  hearer  of  like  intelligence.  Addi- 
tional interest  attaches  to  the  chapter  on  the  control  of  land 
forms  by  special  climatic  conditions  when  it  is  shown  that 
climate  is  not  constant,  but  that  in  certain  parts  of  the  world 
the  climate  of  the  recent  past  (as  the  earth  counts  time)  has 
been  different  from  that  prevailing  to-day,  and  that  many  marks 
of  the  past  climate  are  still  distinct  in  the  existing  topography. 
Thus  topographical  forms  produced  under  the  former  normal 
climate  of  many  basins  now  arid,  and  under  former  glacial 
climate  of  many  regions  now  normal,  are  appropriately  intro- 
duced, on  branches  that  depart  in  an  orderly  fashion  from  the 
main  theme ;  and  this  I  hold  to  be  just  as  important  in  geog- 
raphy as  in  geometry. 

Shore-Lines.  The  chapter  on  shore -lines  may  be  advisedly 
placed  at  the  end  of  a  general  course  on  physical  geography, 
for  it  cannot  be  introduced  earlier  without  interrupting  the 
sequence  of  chapters  just  sketched,  and  because  it  fittingly 
follows  all  of  them.  It  is  entirely  inappropriate  as  a  part  of  the 


144  EDUCATIONAL  ESSAYS 

study  of  the  oceans,  although  it  was  there  placed  by  Peschel. 
The  natural  association  of  this  topic  is  with  the  forms  of  the 
land.  One  of  the  most  pleasing  results  of  the  rational  study 
of  shore-lines  is  the  discovery  that  their  development  may  be 
treated  just  as  systematically  as  that  of  land  forms ;  and  indeed 
that  many  general  principles  established  in  the  study  of  land 
forms  as  affected  by  the  sub-aerial  agencies  of  erosion  are 
equally  applicable  to  the  seashore,  when  allowance  is  made  for 
the  marine  agencies  of  erosion  there  in  action. 

Plants,  Animals,  and  Man.  It  may  be  noticed  that  no  place 
is  given  in  the  list  of  topics  here  considered  to  plants,  or  ani- 
mals, or  man.  This  is  because  organic  forms  do  not  in  them- 
selves constitute  any  part  of  the  content  of  physical  geography, 
however  largely  they  may  enter  into  geography  proper.  It  is 
therefore  proper  not  to  place  Plants,  Animals,  and  Man  as 
chapter  headings  equivalent  to  Plains,  Rivers,  or  Shore-lines, 
unless  merely  with  the  intention  of  gathering  in  one  place  and 
emphasizing  the  "consequences"  already  presented  in  connec- 
tion with  their  physiographic  controls ;  but,  on  the  other  hand, 
it  is  extremely  desirable'  that  plants,  animals,  and  man  should 
receive  frequent  mention  in  every  chapter,  in  illustration  of  the 
organic  consequences  that  follow  from  controls  exerted  by  phys- 
ical environment  or  organic  opportunity.  Herein  the  method  of 
the  American  school,  if  the  recommendation  of  the  sub-commit- 
tee of  the  National  Educational  Association  may  be  so  called, 
differs  distinctly  from  that  of  the  European,  in  which  the  phys- 
ical features  of  the  earth  are  considered  for  themselves  alone 
and  without  regard  to  the  conditions,  favorable  or  unfavorable, 
that  they  offer  for  life,  be  it  low  or  high.  The  omission  of  "  con- 
sequences "  seems  to  me  almost  as  unfortunate  as  would  be  the 
omission  of  "  causes." 

Regional  Geography.  There  is  another  omission  from  the 
content  of  the  subject  as  outlined  above  that  may  excite  com- 
ment. The  regional  study  of  the  several  continents,  as  made  up 
of  physical  features  of  various  kinds,  is  not  attempted.  This  is 
because  it  is  not  possible  to  give  both  a  general  and  regional 
course  on  physical  geography  in  a  single  year.  Neither  part  of 
the  course  could  be  properly  developed  in  so  short  a  time.  It 


PHYSICAL  GEOGRAPHY  IN  THE  HIGH  SCHOOL     145 

is  true  that  some  knowledge  of  the  physical  geography  of  North 
America  and  Europe  is  very  important  ;  indeed,  that  it  ought 
not  to  be  sacrificed  to  the  impossible  by  attempting  to  present 
the  physical  features  of  all  the  continents  as  a  supplement  to 
the  general  principles  of  physical  geography  in  a  single  year. 
Instead  of  teaching  the  regional  physical  geography  of  even 
North  America  and  Europe  in  the  general  course,  it  is  better  to 
use  many  features  from  these  grand  divisions  as  type  examples 
in  the  several  chapters  to  which  they  belong,  always  locating 
the  examples  by  reference  to  maps.  Clear  ideas  of  some  few 
things  will  thus  be  gained,  instead  of  vague  and  imperfect  ideas 
of  many  things.  If  there  is  time  to  spare,  a  following  course  on 
the  physical  geography  of  the  continents  would  be  interesting 
and  profitable ;  but  as  part  of  a  general  course  this  subject 
cannot  receive  adequate  attention. 


VIII 
THE  NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY 

Geography  should  have  a  place  in  the  list  of  studies  of  our 
colleges  and  universities  because  the  recognition  implied  in 
giving  it  a  place  is  an  essential  part  of  the  round  of  attentions 
that  the  subject  deserves.  At  present  there  is  nearly  every- 
where a  break  between  the  work  on  the  elementary,  ordinary, 
and  rather  old-fashioned  geography  of  the  schools  and  the  work 
of  the  investigating  and  professional  geographer  in  his  explora- 
tions or  other  advanced  studies.  In  consequence  of  this  break, 
the  general  subject  of  geography  is  not  advancing  as  so  impor- 
tant a  subject  ought  to  advance. 

As  a  result  of  the  break  between  school  geography  and  pro- 
fessional geography,  our  professional  geographers  are  all  self- 
made  men.  They  have  had  to  bridge  over  the  gap  from  their 
school  studies  to  their  professional  labors  in  such  ways  as  they 
could  best  devise.  They  have  consequently  had  to  begin  their 
higher  work  with  preparation  inferior  to  that  which  they  should 
have  had  ;  and  they  have  generally  concluded  it  without  coming 
personally,  or  through  their  writings,  in  close  contact  with  our 
teachers  of  geography,  who,  of  all  persons  in  the  community, 
should  be  most  promptly  supplied  with  everything  which  is 
new  concerning  their  subject.  The  break  in  the  study  and 
development  of  the  subject  is  therefore  both  in  the  ascending 
and  descending  order  of  educational  attentions,  and  this  I  shall 
now  endeavor  to  show  more  fully. 

It  is  not  a  little  curious  that  a  subject  of  such  fundamental 
importance  and  wide  application  should  so  seldom  be  regarded 
as  affording  material  for  serious  collegiate  study.  There  is,  to 
be  sure,  not  infrequently  an  elementary  course  in  physical  geog- 
raphy announced  in  college  catalogues  ;  but  this  is  in  nearly 
all  cases  given  by  men  whose  first  attention  is  turned  to  other 
subjects.  The  course,  as  given,  can  do  nothing  more  than  open 

146 


NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY       147 

the  study,  as  a  simple  elementary  course  in  history  or  botany 
might  open  these  attractive  subjects.  But  while  the  higher 
study  of  history  and  botany  is  well  provided  for,  opportunity 
for  continued  study  in  geography  is  seldom  allowed ;  and 
geographical  investigation  is  hardly  known  among  us. 

Perhaps  one  reason  for  this  unfortunate  neglect  is  the 
assumption  that  geography  proper  is  finished  in  the  schools, 
and  that  physical  geography  is  completed  in  the  single  course 
that  is  allowed,  in  the  colleges,  and  that  there  is  therefore  no 
material  for  further  teaching.  Judging  by  the  scarcity  of 
geographical  text-books  of  advanced  quality  in  our  language, 
good  argument  might  be  made  to  this  conclusion,  especially 
by  those  professors  of  other  subjects  who  have  the  college 
courses  in  physical  geography  in  their  hands,  and  who  cannot 
of  course  be  expected  to  develop  or  originate  higher  courses, 
but  only  to  reproduce  the  subject  about  in  the  form  that  it 
is  left  by  others. 

Another  reason  that  might  be  offered  for  the  discontinuance 
of  geographical  studies  is  that  geography  is  properly  continued 
in  history  and  that  physical  geography  finds  its  later  develop- 
ment in  geology ;  but  this  view  cannot  be  accepted  by  those 
who  recognize  the  fullness  of  geography  as  a  subject  in  itself, 
or  by  those  who  know  how  completely  the  geographical  ele- 
ment is  subordinated  in  the  usual  presentation  of  history  and 
geology.  It  might  as  well  be  urged  that  geography  is  suffi- 
ciently continued  in  zoology  or  botany,  because  the  study  of 
animals  and  plants  involves  the  study  of  their  distribution 
over  the  earth.  In  order  to  perceive  more  clearly  this  break 
in  the  ascending  order  of  attentions,  let  us  briefly  trace  the 
position  of  geography  through  our  educational  system. 

At  first,  in  the  lower  classes  of  the  grammar  schools,  geog- 
raphy is  a  congeries  of  subjects  including,  besides  a  central 
body  of  real  geographical  material,  various  side  issues  about 
astronomy,  physics,  mineralogy,  geology,  zoology,  botany, 
history,  government,  and  economics.  This  is  as  it  should  be ; 
under  the  broad  subject  of  elementary  geography  the  young 
scholar  naturally  makes  acquaintance  with  related  subjects  that 
are  afterward  considered  separately.  Perhaps  the  distinguishing 


1 48  EDUCATIONAL   ESSAYS 

mark  of  the  newer  order  of  things  in  school  geography  is  the 
increased  share  of  explanatory  and  rational  physiography  that  it 
includes,  as  contrasting  with  the  empirical  descriptive  geography 
of  earlier  methods ;  and  this  replacement  is  a  hopeful  sign  of 
what  must  eventually  follow,  but  of  which  there  is  as  yet  not 
very  much  indication.  A  prevailing  deficiency  of  existing  ele- 
mentary methods  is  the  failure  to  make  enough  use  of  the  natural 
illustrations  of  the  subject  that  abound  around  all  schools  in  the 
city  and  country.  There  is  valiant  effort  made  by  many  earnest 
teachers  to  escape  from  subjection  to  the  text-book,  but  the 
small  variety  of  available  elementary  literature  on  geographical 
subjects  makes  this  effort  a  difficult  one. 

In  the  later  grammar-school  years  geography  is  generally 
replaced  with  history,  the  natural  successor  of  political  geog- 
raphy, for  this  is  only  history  in  its  most  elementary  form. 
The  replacement  continues  in  the  high  school,  and  here  the 
various  other  subjects  first  encountered  under  geography  are, 
as  a  rule,  also  given  individual  place,  —  astronomy,  physics, 
physical  geography  (including  meteorology),  botany,  zoology, 
and  occasionally  mineralogy  and  geology ;  although  the  last 
subject  is  too  often  unhappily  treated  by  beginning  with  a  book 
instead  of  in  the  field,  the  natural  geological  laboratory  with 
which  country  schools  at  least  are  so  well  provided.  As  far  as 
physical  geography  is  concerned,  the  high-school  course  suffers 
from  lack  of  illustrative  material  as  well  as  from  the  small 
variety  of  good  books  for  side  reading.  Normal  schools  too 
often  fail  to  give  a  clear  understanding  of  the  physiographic 
aspects  of  geography  to  their  embryonic  teachers,  because  they 
place  so  little  emphasis  on  the  needed  geological  basis  of 
the  subject,  and  especially  on  the  field  study  of  geology. 
They  likewise  fail  to  familiarize  their  students  by  observation 
sufficiently  with  elementary  facts  about  the  apparent  move- 
ment of  the  sun,  the  winds,  and  other  commonplace  phenomena 
which  are  of  great  educational  value  in  the  early  stages  of 
geography.  As  a  result,  most  children  learn  from  a  book,  and 
not  from  the  sky,  that  the  sun's  noon  altitude  and  the  length 
of  the  days  change  with  the  seasons.  This  not  only  teaches 
the  subject  badly,  but  also  dulls  the  child's  observation  and 


NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY       149 

intelligence  by  failing  to  give  him  a  legitimate  opportunity 
for  exercise.  I  believe  that  in  most  cases  it  would  be  more 
advantageous  to  the  teacher's  future  worth  to  devote  less  time 
in  normal  schools  to  comparatively  abstract  philosophical  and 
psychological  studies,  and  more  time  to  subjects  that  will  have 
an  immediate  application  in  school  work. 

All  .the  branches  from  elementary  geography  that  are  spe- 
cialized in  the  high  school  have  more  or  less  recognition  in 
college  and  university  studies,  but  geography  itself  has  practi- 
cally none,  and  physical  geography  has  too  little  for  its  needs. 
Yet  who  can  doubt  that  the  very  subjects  which  constitute 
the  core  of  school  geography  are  worthy  of  broader  treatment 
in  college,  and  of  investigation  in  the  university.  The  geog- 
raphy of  the  grand  divisions  of  the  lands  is  susceptible  of 
expanded  collegiate  treatment  such  as  it  receives  at  not  a  few 
German  gymnasia  and  universities.  Economic  geography,  a 
consideration  of  the  larger  aspects  of  commercial  geography, 
might  be  made  a  most  useful  collegiate  associate  of  economics. 
So  with  physical  geography,  and  especially  with  the  modern 
aspects  of  the  subject  for  which  many  prefer  the  special  name 
of  physiography.  Here  is  a  subject,  the  outgrowth  of  modern 
geology,  whose  educational  values  are  as  yet  hardly  sounded, 
but  whose  attractions  are  everywhere  admitted  ;  nevertheless 
it  is  seldom  allowed  adequate  recognition  by  being  made  the 
first  responsibility  of  a  college  professor.  Still  less  frequently 
is  it  made  the  field  of  investigation  in  higher  university  work, 
although  its  promise  of  fruitful  return  is  not  exceeded  by  that 
of  any  other  of  the  subjects  to  which  attention  is  now  so  gener- 
ally turned  by  means  of  advanced  courses,  laboratory  facilities, 
and  especially  prepared  teachers.  In  all  this  we  are  not  behind 
the  English  universities,  but  we  are  far  behind  those  of  Ger- 
many, where  professorships  in  geography  are  not  uncommon. 

In  another  branch  of  educational  ascent  the  insufficient 
attention  allowed  to  physical  geography  is  painfully  marked. 
This  is  in  those  scientific  schools  which  teach  engineering,  and 
whose  students  furnish  the  topographical  surveyors  by  whom 
our  national  and  state  surveys  are  made.  So  strongly  is  the 
attention  of  the  faculties  of  these  schools  turned  toward  the 


150  EDUCATIONAL  ESSAYS 

mathematical  and  technical  sides  of  the  instruction  that  is 
required  as  preparation  for  methods  of  work  employed  by  the 
topographer  and  engineer,  that  little  time  is  left  for  the  study 
of  the  great  subject  of  the  topographer's  attention ;  namely, 
the  surface  of  the  earth  and  the  expression  of  its  wonderfully 
modulated  forms.  The  young  men  who  are  graduated  from 
scientific  schools  and  who  undertake  the  responsible  task  of 
mapping  our  country  in  state  and  national  surveys  must,  with 
few  exceptions,  begin  the  work  with  no  adequate  understand- 
ing of  the  subject  they  are  to  work  upon,  although  they  may 
be  well  instructed  as  to  the  use  of  the  level  and  the  plane  table 
with  which,  they  are  to  work. 

There  is  one  phase  of  this  subject  of  map  making  that  is 
not  generally  understood.  It  is  too  commonly  supposed  that 
a  map  is  made  entirely  by  measurement ;  that  it  is  necessarily 
accurate  because  the  topographer  carefully  measured  the 
forms  of  the  land  before  him  when  the  map  was  made.  Now, 
while  it  occasionally  happens  that  an  elaborately  measured  sur- 
vey has  been  made,  —  as,  for  example,  of  the  area  of  Central 
Park  in  New  York  City,  for  the  use  of  the  landscape  gardener 
by  whom  its  natural  beauties  were  so  well  utilized,  —  it  is 
practically  never  the  case  in  this  country  that  a  minutely  elabo- 
rate method  is  employed  on  government  surveys  of  large  areas. 
The  surveyor  fixes  by  accurate  measurement  a  certain  number 
of  points,  but  between  these  points  he  must  sketch  the  inter- 
vening space.  In  sketching,  he  has  to  reduce  the  area  of  the 
ground  before  him  to  a  much  smaller  area  on  his  map  sheet ; 
and  he  must  therefore  omit  many  details  and  represent  only 
the  more  important  features.  The  process  of  selection  and 
omission  should  involve  intelligent  and  systematic  generaliza- 
tion based  upon  an  appreciation  of  the  meaning  of  the  land- 
scape and  on  an  understanding  of  the  relation  of  its  primary, 
secondary,  and  subordinate  features.  Without  such  generaliza- 
tion the  map  produced  is  inexpressive,  a  poor  piece  of  work. 
If  the  topographer  actually  measured  every  line  that  he  draws, 
he  might  be  as  unintelligent  but  as  faithful  as  a  camera ;  but 
he  must  generalize,  and  to  do  this  he  must  have  an  intelligent 
understanding  of  this  subject  —  n  ?  intelligence  du  terrain"  as 


NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY       151 

a  competent  French  writer  has  lately  expressed  it.  But  at 
present  the  topographer  receives  only  the  barest  introduction 
to  this  division  of  his  life  work  in  the  professional  school. 
The  instruction  that  he  may  have  had  in  physical  geography 
is  largely  concerned  with  the  larger  features  of  the  distribution 
of  land  and  water  and  with  the  greater  relief  forms  of  land 
which  he  never  sees  as  a  whole,  and  too  little  concerned  with  a 
careful  study,  classification,  and  explanation  of  the  more  minute 
land  forms  with  which  he  will  be  chiefly  occupied  all  his  life. 
He  therefore  goes  into  the  field  unprepared  for  some  of  his  most 
important  duties,  and  if  he  ever  learns  them  (some  topographers 
never  do),  it  is  only  at  the  expense  of  many  seasons  of  costly 
experience.  The  larger  features  of  the  world  deserve  all  the 
attention  that  they  receive  in  his  education,  but  their  value  is 
chiefly  in  contributing  to  the  development  of  his  general  intelli- 
gence, not  of  his  professional  skill.  The  smaller  features  of  land 
form  are  not  systematically  taught  in  any  engineering  school  in 
this  country,  as  far  as  I  have  been  able  to  learn.  Until  they 
are,  the  topographer  will  be  graduated  with  one  important  side 
of  his  professional  education  neglected. 

Now,  in  contrast  to  the  existing  condition  of  geographical 
teaching,  let  us  briefly  consider  the  ideal  sequence  of  geo- 
graphical studies  from  the  bottom  to  the  top  of  the  educa- 
tional system,  and  sketch  out  at  the  same  time  the  ideal 
equipment  necessary  for  the  best  work  in  each  step  of  the 
ascending  scale. 

The  grammar  schools  would,  as  a  rule,  follow  their  present 
plan  as  to  time,  but  their  geographical  work  would  be  better 
done.  Great  care  would  be  taken  to  give  just  ideas,  especially 
at  the  beginning  of  the  study.  More  use  would  be  made  of 
outdoor  observation  of  many  kinds.  A  greater  share  of 
physiographic  work  would  be  introduced,  thus  emphasizing 
the  rational  side  of  the  study  and  displacing  something  of  the 
empirical  descriptive  and  political  geography  that  now  takes 
up  too  much  time.  The  teacher  would  be  expected  to  have 
practical  knowledge  based  on  manual  exercises  and  field 
observation  of  the  various  practical  steps  in  the  education  of 
her  scholars  ;  and  in  every  step  her  experience  should  have  a 


152  EDUCATIONAL  ESSAYS 

greater,  broader  extension  than  can  be  expected  of  the  boys  and 
girls  in  her  charge.  As  to  equipment,  there  would  be  a  great 
increase  in  the  number  of  available  text-books,  manuals,  and 
readers,  and,  let  us  hope,  a  general  improvement  in  their  quality 
as  well.  We  should  hope  to  find  every  grammar  school  pro- 
vided with  a  good  topographical  map  of  its  district  and  a  good 
topographical  map  of  its  state,  with  a  well-illustrated  text 
explanatory  of  the  latter  and  therefore  including  some  account 
of  the  former.  State  maps  are  already  distributed  in  the  schools 
of  New  Jersey  and  Rhode  Island,  but  they  are  not  accom- 
panied by  explanatory  texts,  and  their  usefulness  is  therefore 
greatly  decreased.  Good  models  of  typical  land  forms  would 
be  of  great  value,  but  practically  none  are  now  on  the  market. 
A  good  collection  of  wall  maps  is  essential.  Small  elementary 
globes  for  hand  study  by  each  scholar  are  of  great  importance, 
not  so  much  for  teaching  what  used  to  be  called  "  the  use  of 
the  globes,"  but  for  implanting  correct  introductory  ideas  of 
the  forms  and  distribution  of  land  and  water.  In  the  private 
libraries  of  those  teachers  who  felt  a  special  fondness  for  this 
division  of  their  work,  we  should  expect  to  see  maps  and  texts 
upon  adjacent  states.  There  should  be,  if  possible,  a  project- 
ing lantern,  and  a  general  collection  of  geographical  lantern 
slides,  and  some  of  the  governmental  maps  of  the  kind  referred 
to  below.'  Current  weather  maps  should  be  accessible  during 
part  of  the  year  at  least,  and  simple  meteorological  records 
should  be  made  to  serve  as  the  foundation  of  later  systematic 
study.  Besides  the  thermometer  usually  kept  in  the  school- 
room for  hygienic  purposes,  another  should  be  provided  for 
outdoor  observations. 

In  the  ideal  high-school  course  the  geographical  basis  of 
history,  zoology,  and  botany  should  be  carefully  presented 
whenever  those  subjects  are  taught.  Physical  geography  in  its 
more  modern  form,  based  on  simple  geological  principles, 
would  replace  the  more  descriptive  treatment  of  the  subject 
now  in  vogue.  Meteorology  might  well  have  a  half  year  to 
itself,  for  it  is  a  subject  that  is  capable  of  most  satisfactory 
use  as  a  mental  discipline.  The  teacher  should  of  course  be 
well  versed  in  all  the  observational  work  that  is  expected  of 


NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY       153 

her  scholars,  and  her  experience  in  field  study  should  cover  a 
much  wider  range  than  is  possible  around  the  school  where  she 
teaches.  What  has  already  been  said  of  normal  schools  will 
indicate  something  of  the  changes  that  seem  to  me  most  needed 
there.  The  teacher  of  geography  in  the  normal  schools  should 
in  every  case  have  good  training  in  geological  field  work. 
Through  no  other  discipline  can  the  necessary  command  of 
the  subject  be  acquired. 

In  the  high-school  and  normal-school  libraries  the  map  col- 
lection would  include  an  extended  series  of  wall  maps  and  a 
whole  set  of  large-scale  topographical  sheets  of  the  state  and 
perhaps  of  some  of  the  adjacent  states,  as  well  as  the  general 
maps  of  the  home  state  and  its  neighbors,  each  with  its  appro- 
priate text.  There  would  also  be  a  selected  list  of  lantern 
slides,  particularly  illustrative  of  the  features  of  the  home 
state.  There  should  be  a  considerable  number  of  various 
governmental  maps,  of  which  we  now  have  so  large  a  variety 
procurable  at  so  low  a  cost,  such  as  the  charts  of  the  coast,  of 
the  Mississippi  river,  and  of  various  topographical  features  like 
canons,  mesas,  bays,  deltas,  etc.,  in  different  parts  of  the 
country.1  These  are  of  great  value  in  giving  large-scale  illus- 
trations of  actual  and  important  geographical  features.  A  col- 
lection of  well-made  models  would  also  be  extremely  serviceable. 
For  supplementary  reading,  a  good  journal  of  school  geography 
is  very  desirable ;  a  valuable  publication  of  this  kind  exists  in 
Germany,  and  we  may  in  time  have  one  in  this  country.  It 
would  be  particularly  useful  in  the  normal  schools,  and  from 
them  would  work  its  way  into  other  schools. 

Some  indication  has  already  been  given  of  the  nature  of  the 
geographical  instruction  that  is  needed  in  our  colleges.  The 
chief  requirements  of  the  desired  courses  would  be  that  they 
should  build  upon  the  high-school  preparation ;  that  they  should 
form  the  first  duties  of  the  professor  or  professors  in  charge  of 
them ;  that  they  should  be  thus  developed  in  greater  variety 
and  strength  and  breadth  than  is  now  possible ;  that  they 
should  be  given  not  only  library  collections  but  laboratory 

1  See  Governmental  Maps  for  Use  in  Schools,  by  Messrs.  Davis,  King,  and 
Collie.  Henry  Holt  &  Co.,  New  York,  1894. 


154  EDUCATIONAL  ESSAYS 

facilities  as  well,  where  maps,  models,  and  pictures  could  be 
carefully  studied.  The  specific  courses  most  desired  are 
general  physiography,  general  economic  geography,  special 
geography  of  continental  areas,  the  different  sections  of  the 
last  to  be  given,  if  desired,  only  in  successive  years.  The  geo- 
graphical courses  in  engineering  schools  should  be  in  grade 
similar  to  those  of  the  colleges,  but  in  subject  they  should  be 
more  strictly  limited  to  the  practical  needs  of  the  student. 
For  the  topographical  engineer  the  most  serious  need  is  a 
thorough  course  in  the  physiography  of  the  land,  based  on 
geology  with  field  work.  The  chief  characteristic  of  real  uni- 
versity work  is  embraced  in  the  word  "  opportunity."  The 
opportunity  comes  partly  in  association  with  specialists,  who 
give  lectures  and  hold  conferences  while  carrying  on  their  own 
investigations,  partly  in  the  free  use  of  the  university  collec- 
tions, both  these  opportunities  being  essential  to  the  vigorous 
growth  of  the  young  geographer.  If  he  looks  to  physical 
geography  as  his  chief  study,  he  must  be  well  grounded  in 
geology,  always  including  good  field  training  ;  if  he  specializes 
in  economic  or  commercial  geography,  a  good  knowledge  of 
history  must  be  acquired.  The  associated  subjects  of  meteor- 
ology and  climatology  call  for  preparation  in  physics  and 
mathematics.  Oceanography,  an  undeveloped  specialty,  requires 
knowledge  of  mathematics,  physics,  chemistry,  and  biology. 
In  any  one  of  these  lines  of  work  the  advanced  student  should 
always  strive  to  make  some  original  contribution  to  his  subject. 
The  geographical  collections  of  colleges  and  universities 
would  of  course  include  practically  all  that  has  already  been 
mentioned,  and  in  addition  a  number  of  the  more  important 
geographical  journals  :  Petermanns  Mittheilungen,  the  Geo- 
graphisches  Jahrbuch,  the  (London)  Geographical  Journal,  the 
Scottish  Geographical  Magazine,  and  of  course  all  the  impor- 
tant geographical  journals  published  in  this  country.  Books 
of  travel  should  be  well  represented  in  the  college  library. 
Furthermore,  a  series  of  grouped  sheets  of  foreign  topograph- 
ical surveys,  selected  for  their  illustration  of  special  features, 
will  be  found  of  service.  Geographical  lantern  slides  and 
models  are  also  of  great  value  in  collegiate  as  well  as  in  the 


NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY       155 

earlier  stages  of  instruction ;  such  elaborate  models  as  those 
made  by  Heim  of  Zurich  would  be  especially  appropriate  in  col- 
lege laboratories.  University  collections,  as  differing  from  college 
collections,  should  give  greater  opportunity  for  original  research  ; 
and  for  this  purpose,  besides  an  extended  collection  of  geograph- 
ical literature,  a  series  of  topographical  maps  of  various  countries 
is  of  great  service.  The  expense  of  such  a  collection  is,  however, 
very  great. 

I  shall  not  attempt  to  measure  the  relative  importance  of  these 
various  geographical  courses  in  college  and  university,  for  on  that 
question  my  testimony  would  probably  be  prejudiced  ;  but  it  may 
be  safely  contended  that  they  deserve  more  attention  than  they 
now  receive.  It  is,  however,  plainly  out  of  the  question  for  all  of 
our  colleges  and  universities  to  undertake  the  whole  round  of  geo- 
graphical studies  here  outlined  and  do  equal  justice  to  other  sub- 
jects at  the  same  time.  Even  our  largest  universities  fall  short 
of  the  ideal  here  indicated,  and  there  is  no  likelihood  that  all  of 
them  will  reach  it  in  any  short  time.  Moreover,  educators  who 
are  interested  in  other  subjects  generally  contend  that  they  also 
need  and  deserve  a  fuller  attention  than  they  receive.  It  is  not 
probable  that  any  one  institution  will  be  so  fortunate  as  to  be  able 
to  treat  all  subjects  with  the  fullness  that  the  specialists  in  each 
could  desire.  The  solution  of  the  difficulty  is  not  so  likely  to  be 
found  in  enormous  endowments  as  it  is  in  the  wise  distribution 
of  efforts  among  neighboring  institutions.  When  several  colleges 
in  a  single  state  recognize  that  they  cannot  all  teach  all  subjects, 
they  may  perhaps  agree  to  develop  individually,  one  in  some  sci- 
entific direction,  another  as  a  classical  institution,  a  third  as  a 
historical,  and  a  fourth  as  a  mathematical  center.  Each  might 
then  give  due  attention  to  the  general  need  of  more  elementary 
studies,  and  each  might  become  well  equipped  in  the  field  that 
it  especially  cultivates.  The  serious  student  could  then  resort 
to  the  institution  which  gave  his  preferred  studies  the  greatest 
care ;  he  might  follow  the  practice,  not  uncommon  abroad,  of 
going  in  his  later  college  years  from  one  institution  to  ano'ther, 
in  order  to  get  from  each  what  it  could  give  best.  Hearty  co- 
operation instead  of  silent  or  ill-concealed  rivalry  might  then 
prevail.  If  four  or  five  colleges  or  universities,  well  distributed 


156  EDUCATIONAL  ESSAYS 

over  the  country,  included  geography  along  with  geology  under 
the  group  of  scientific  subjects  that  they  would  cultivate  most 
highly,  geographers  should  for  many  years  be  well  content.  It 
is  not  to  be  expected  that  advanced  geographical  courses  should 
be  largely  attended.  They  will  never  "  pay  "  for  the  cost  of  their 
establishment,  but  fortunately  this  criterion  is  not  one  that  will 
determine  the  advisability  of  establishing  them  in  the  more  lib- 
eral universities.  When  geographical  courses  come  to  be  recog- 
nized as  important  parts  of  collegiate  and  higher  study,  they  will 
be  provided  for,  even  if  not  attended  by  large  classes  of  students. 

It  is  not,  however,  my  intention  to  give  at  this  time  so  much 
attention  to  the  outlines  of  geographical  courses  that  are  needed 
in  our  higher  institutions  of  learning  as  it  is  to  indicate  the 
need  that  is  felt  for  these  courses  both  in  the  work  of  the  pro- 
fessional geographer  and  in  the  teaching  of  geography  in  the 
lower  schools. 

Allusion  has  been  made  in  several  paragraphs  to  "  profes- 
sional geographers."  They  do  not  form  a  large  class  of  the 
scientific  or  technical  community,  but  they  include  so  many  dif- 
ferent classes  of  workers  that  it  seems  best  to  enumerate  them 
more  in  detail. 

The  topographical  surveyor  has  already  been  considered.  Next 
let  us  review  the  work  of  the  cartographer,  or  professional  map 
maker,  even  though  he  might  not  consider  himself  a  professional 
geographer.  He  is  a  specialist  in  these  modern  days,  for  he  does 
little  work  on  other  subjects  than  maps;  hence,  although  an 
artist  primarily,  he  is  so  distinctly  concerned  with  geographical 
subjects  that  he  may  be  included  with  geographers.  His  duty  is, 
at  first  sight,  merely  to  copy  faithfully  the  original  field  map 
that  is  presented  for  publication,  and  as  far  as  such  copying 
goes,  he  is  aided  much  by  photography ;  but  when  his  copying 
involves  reduction  of  scale  or  redrawing,  it  may  be  far  from 
successful  if  the  artist  has  no  appreciation  of  his  subject.  If 
the  map  is  to  be  reduced  in  scale,  problems  of  selection  and 
generalization  are  presented  to  the  map  maker  not  unlike  those 
encountered  by  the  topographer ;  and  one  has  only  to  compare 
different  small-scale  maps  of  the  same  region  to  see  what  cari- 
catures they  often  are  of  the  true  outlines.  It  would  often  seem 


NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY       157 

as  if  the  artist  had  no  idea  that  river  courses,  shore-lines,  and 
mountain  ranges  have  individual  expressions  which  must  be 
intelligently  preserved,  when  shown  at  all,  if  the  map  is  to  be 
faithful  to  nature,  even  though  its  scale  is  small.  There  are,  of 
course,  some  map  makers  who  are  well  prepared  for  their  pro- 
fession, but  few  of  them  are  in  this  country.  We  do  not  often 
read  here,  as  we  may,  not  infrequently,  in  the  advertisements  on 
Petermanns  Mittheilungen :  "  Wissenschaftlicher  Kartograph, 
vielseitig  gebildet,  durchaus  selbstandige  Kraft,  wiinscht  karto- 
graphische  Arbeiten  zu  iibernehmen ;  "  or  "  Kartograph,  tiich- 
tiger  Zeichner  mit  geographische  Fachkenntnissen,  "  etc.  We 
shall  not  produce  the  highest  class  of  maps  until  scientific  as 
well  as  technical  preparation  is  expected  of  the  draughtsman. 
Although  few  persons  enter  this  profession,  and  although  they 
seldom  attain  individual  reputation  outside  of  their  craft,  never- 
theless their  works  are  widespread,  and  from  beginning  to  end 
of  educational  progress  they  determine  a  large  number  of  geo- 
graphical conceptions  ;  hence  the  work  should  be  good  and  the 
workers  well  prepared  for  the  work.  But  until  the  cartographer 
is  educated  to  select,  omit,  and  generalize  with  appreciative 
skill,  his  maps  will  be  inexpressive.  Many  an  example  of  inex- 
pressive maps  in  school  books  might  be  given,  and  a  few  exam- 
ples of  good  school  maps  might  be  found  to  present  by  way  of 
contrast ;  but  to  that  I  shall  not  turn  here,  reserving  it  for  a 
special  article  elsewhere. 

The  explorer  so  often  directs  his  attention  to  other  subjects 
than  careful  description  of  the  lands  over  which  he  travels  that 
he  cannot  in  all  cases  be  called  a  geographer  ;  but  most  explorers 
have  geography  as  a  prime  subject  before  them,  and  they  ought 
therefore  to  be  trained  geographers ;  but  unfortunately  this  is 
seldom  the  case.  The  usual  accounts  of  travel  in  remote  regions 
by  brave  and  energetic  searchers  after  novelty  give  little  indica- 
tion of  careful  preparation  for  geographical  observation.  The 
untrained  traveler  does  not,  in  the  first  place,  really  see  nearly 
all  the  facts  that  are  before  him ;  for  seeing  requires  trained 
sight.  He  may  look  at  them  day  after  day,  but  many  of  them 
make  no  conscious  impression.  Although  he,  of  course,  recog- 
nizes the  more  important  elements  of  form,  he  is  generally 


158  EDUCATIONAL  ESSAYS 

ignorant  of  their  natural  associates,  and  hence  fails  to  search  for 
them ;  or,  if  he  finds  them  by  chance,  he  does  not  record  them 
systematically.  The  records  that  he  makes  are  in  untechnical 
language,  partly  because  he  is  seldom  well  versed  in  the  limited 
number  of  technical  geographical  terms  already  invented,  partly 
for  the  more  serious  reason  that  there  is  as  yet  so  little  devel- 
opment of  scientific  geographical  terminology  that  the  art  of  accu- 
rate geographical  description  necessarily  remains  for  the  present 
in  a  backward  state.  If  the  explorer  finds  something  which  he 
attempts  not  only  to  describe  but  to  explain,  the  chances  are  that 
he  will  make  a  mistake,  for  he  is  not  trained  in  the  interpreta- 
tion of  past  processes  through  present  forms.  The  only  way  in 
which  these  deficiencies  in  the  explorer's  work  can  be  corrected 
is  by  systematic  geographical  training  of  high  collegiate  grade. 

The  reports  of  our  state  and  national  surveys,  as  well  as  those 
of  Europe,  usually  contain  chapters  of  more  or  less  detail  con- 
cerning the  physical  geography  of  their  districts.  These  are  of 
course  written  by  geologists,  for  it  is  not  yet  the  practice  for 
such  surveys  to  recognize  the  geographer  as  a  specialist  distinct 
from  the  geologist,  nor  even  to  require  that  a  knowledge  of  the 
two  subjects  should  be  combined  in  the  geologist.  The  chapters 
referred  to  hardly  constitute  more  than  a  fair  beginning  of  what 
is  wanted,  although  in  recent  years  there  are  certain  notable  ex- 
ceptions to  this  statement.  In  those  state  surveys  that  are  con- 
cerned with  the  general  natural  history  of  their  domain,  careful 
study  of  geographical  features  by  well-prepared  specialists  is  as 
worthy  an  object  of  attention  as  the  careful  study  of  petrography, 
or  as  the  study  of  birds,  or  Crustacea.  This  is  particularly  true 
when  it  is  remembered  that  the  survey  reports  are  prepared  not 
simply  for  use  by  professional  experts,  but  for  the  body  of  intel- 
ligent, yet  not  professional,  people  of  the  state.  That  this  is  so 
is  often  indicated  by  the  presence  of  several  general  explanatory 
chapters  by  way  of  introduction  to  the  more  technical  parts  of 
the  reports.  To  this  class  of  readers,  geographical  descriptions 
are  particularly  appropriate. 

Again,  for  our  school-teachers  :  it  is  too  much  to  expect  them 
to  struggle  through  the  technical  chapters  on  geology,  petrog- 
raphy, and  paleontology,  in  search  of  information  about  their 


NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY       159 

home  state  for  use  in  teaching.  But  they  would  eagerly  study 
geographical  chapters,  and  would,  moreover,  use  them  to  the 
great  improvement  of  their  school  work.  It  is  curious  that  our 
state  surveyors  have  not  recognized  that,  by  .attracting  the  inter- 
ests of  a  large  body  of  teachers,  they  would  secure  a  new  sup- 
port for  their  legislative  appropriations  ;  and  that  additional 
support  is  often  wanted  is  only  too  plainly  shown  by  the  insta- 
bility of  many  of  the  surveys.  Nothing  would  so  generally  secure 
this  as  chapters  on  local  geography,  prepared  expressly  for  the 
use  of  the  teachers  of  the  state.  At  least  some  of  the  geologists 
on  the  surveys  ought  to  be  geographers  as  well.1 

Writers  of  geographical  text-books  ought,  of  course,  to  be 
geographers,  yet  it  is  only  too  manifest,  on  examining  such 
books,  that  their  authors  are  seldom  trained  in  the  scientific 
phases  of  their  fundamental  subject.  It  is  hardly  surprising  that 
they  are  untrained,  for,  if  not  self-taught,  the  training  that  they 
need  can  be  had  at  very  few  places  in  this  country. 

It  is  perhaps  on  account  of  the  lack  of  opportunity  for  profes- 
sional training  in  geography  that  professorships  in  this  subject 
are  not  more  generally  established  ;  but  this  can  hardly  be  more 
than  a  subordinate  reason.  If  geographers  were  actively  called 
for,  they  would  certainly  be  forthcoming,  even  if  special  study 
in  Europe  were  necessary  for  their  preparation.  Such  was  the 
case  with  petrographers  a  few  years  ago,  but  there  is  no  lack  of 
them  now,  and  no  lack  of  opportunity  for  their  instruction  in 
our  own  colleges. 

There  is  much  said  about  the  connection  between  history  and 
geography  ;  but  inasmuch  as  few,  if  any,  historians  are  proficient 
in  minute  geographical  knowledge,  except  so  far  as  it  concerns 
the  mere  location  of  various  important  points,  it  seems  warrant- 
able to  suppose  that  a  new  light  may  be  shed  on  the  connection 
between  the  two  studies  when  it  is  examined  by  experts  who 
are  well  qualified  in  the  two  subjects  that  are  concerned.  The 
young  historian,  who  inquires  for  a  field  in  which  he  may  gather 

1  I  have  elsewhere  enlarged  upon  this  subject :  "  The  Improvement  of  Geo- 
graphical Teaching,"  National- Geographical  Magazine,  V  (1893),  68;  "A  Step 
toward  Improvement  in  Teaching  Geography,"  Leaflet  No.  u,  January,  1894,  Har- 
vard Teachers'  Association  ;  "  Geographical  Work  for  State  Geological  Surveys," 
Bulletin  of  the  Geological  Society  of  America,  V  (1893),  604-608. 


160  EDUCATIONAL  ESSAYS 

a  neglected  harvest,  can  find  it  in  the  space  between  these  two 
generally  separated  areas  of  study,  or  rather  in  the  space  where 
the  two  ought  to  overlap. 

It  appears,  then,  that  explorers,  topographers,  cartographers, 
teachers,  and  writers  on  geography  all  lack  adequate  preparation 
in  their  chosen  subject.  Compare  their  opportunities  in  school 
and  college  with  those  opened  to  students  who  decide  on  a  career 
as  chemists,  physicists,  zoologists,  or  botanists.  In  these  subjects 
there  is  an  elaborate  series  of  courses  of  instruction  under  care- 
fully prepared  instructors,  all  aided  by  well-equipped  laboratories, 
all  supported  by  extended  collections  of  text-books,  periodicals, 
and  advanced  memoirs.  The  young  man  or  woman  who  wishes 
to  enter  upon  a  life  work  in  any  of  these  studies  may  prepare  for 
it  by  as  many  years  of  well-directed  study  under  experts  as  his 
or  her  purse  will  allow.  Any  one  of  these  subjects  may  be  pur- 
sued all  through  many  of  our  larger  colleges  as  the  chief  object 
of  attention  ;  and  in  the  larger  universities,  graduate  courses  are 
provided  in  the  several  subjects,  which  may  easily  occupy  two  or 
three  years.  If  the  student's  funds  are  exhausted,  there  are  gen- 
erally fellowships  for  the  aid  of  those  who  give  promise  of  excel- 
lent work.  At  the  close  of  such  a  preparation  the  student  has  a 
wide  knowledge  of  the  subject  in  general,  and  a  precise  knowl- 
edge of  certain  parts  of  it ;  and  in  his  own  particular  line  he  is 
often  in  advance  of  the  world.  He  is  ready  for  professional 
service  in  scientific  bureaus,  state  experiment  stations,  colleges, 
and  schools.  He  has,  of  course,  still  much  to  learn,  but  what 
he  lacks  chiefly  is  experience  and  the  broader  views  of  the  rela- 
tions of  things  that  come  only  with  living  through  a  period  of 
perhaps  ten  or  twenty  years  after  graduation. 

The  advanced  instruction  in  these  various  subjects  is  not 
maintained  because  it  is  financially  profitable,  but  because  it  is 
the  plain  duty  of  the  university  to  offer  to  those  who  wish  it  an 
opportunity  for  study  in  as  many  of  the  lines  of  higher  research 
as  possible.  Students  who  specialize  in  these  subjects  do  not 
look  forward  to  great  fortunes,  but  rather  to  the  satisfaction  of 
living  an  intellectual  life,  hoping  of  course  that  it  may  lead  to 
some  reasonable  measure  of  home  comfort.  Geography  calls  for 
and  deserves  as  good  an  opportunity  as  that  which  its  associated 


NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY       161 

sciences  enjoy.  When  this  opportunity  is  offered  by  certain  uni- 
versities and  is  widely  known,  explorers  will  be  expected  to  pre- 
pare for  their  work  systematically,  studying  geography,  if  they 
wish  to  be  geographical  explorers,  as  assiduously  as  they  now 
study  botany,  if  they  wish  to  be  botanical  explorers.  Topog- 
raphers will  then  be  expected  to  enter  their  work  reasonably 
well  informed  on  the  meaning  of  the  most  important  subject 
that  will  come  before  them.  Map  publishers  will  not  engage  the 
services  of  young  cartographers  who  cannot  work  intelligently. 
Teachers  in  all  grades  of  geography  will  be  held  to  a  higher  qual- 
ity of  work  than  they  can  now  reach.  The  result  of  all  this  will 
be  the  gradual  introduction  of  a  higher  standard  in  all  that  per- 
tains to  geographical  matters ;  and  the  reaction  from  this  result 
will  be  most  favorably  felt  in  a  better  understanding  of  the  foun- 
dations of  life  and  work  all  around  us.  When  this  time  comes, 
the  ascending  order  of  attentions  that  geography  deserves  will 
be  better  filled  out. 

Let  us  next  consider  the  effect  of  this  geographical  regenera- 
tion on  the  descending  order  of  attentions  by  which  the  results 
gained  through  the  professional  investigators  may  be  passed 
down  into  the  lower  schools,  thus  contributing  their  share  to 
the  enrichment  of  the  early  years  of  education. 

It  is  generally  recognized  that  improvements  in  methods  of 
consideration  and  presentation  in  the  lower  schools  are  intro- 
duced chiefly  by  those  who  have  studied  in  higher  grades  than 
those  in  which  they  teach.  The  recent  report  of  the  Committee 
of  Fifteen  emphasizes  this  principle  by  urging  that  all  teachers 
in  the  elementary  schools  shall  have  had  a  high-school  education, 
and  that  the  high-school  teachers  shall  have  had  a  college  course. 
The  manner  in  which  the  requirements  for  admission  to  college 
determine  improvement  of  teaching  in  the  schools  is  also  a  case 
in  point.  Greater  attention  to  English  composition,  Latin  at 
sight,  laboratory  methods  in  physics,  and  ability  to  deal  with 
original  problems  in  geometry,  —  all  are  associated  either  with 
the  suggestions  of  college  faculties  or  of  school-teachers  who  are 
college  graduates.  It  is  especially  through  the  broadening  influ- 
ences of  college  and  university  work  that  traditional  methods  are 
refreshed  and  that  the  newer  contributions  to  a  subject  are 


1 62  EDUCATIONAL  ESSAYS 

infused  into  the  lower  grades  of  teaching.  Geography  truly  shows 
some  signs  of  awakening  to  the  need  of  modern  knowledge  and 
better  methods  on  the  part  of  its  teachers,  but  little  is  as  yet 
accomplished  in  this  direction  because  of  the  break  between  the 
investigators  and  the  teachers  of  the  secondary  schools.  This  is 
the  interruption  in  the  descending  order  of  attentions,  across 
which  newer  and  better  and  broader  views  now  pass  so  slowly. 

As  this  interruption  is  lessened  by  giving  a  larger  share  to 
geographical  subjects  in  higher  instruction,  two  good  results 
may  be  confidently  expected.  In  the  first  place,  the  method  of 
treatment  of  the  subject  as  a  whole  will  improve,  for  there  is  no 
place  where  so  thorough  a  consideration  is  given  to  the  various 
relations  of  a  subject  as  in  the  advanced  classes  of  a  university. 
Professional  experts  are  apt  to  work  for  themselves  or  for  each 
other,  and  their  manner  of  treatment  therefore  fails  to  include 
the  relation  of  the  higher  and  the  lower  parts  of  their  subject. 
Teachers  in  the  secondary  schools  are,  as  has  already  been  pointed 
out,  very  rarely  acquainted  with  investigation  or  investigators  ; 
they  have  little  share  in  or  association  with  origination;  they  are 
in  nearly  all  cases  closely  limited  to  reproducing  the  statements 
of  text-books.  The  university  professor  has  an  exceptional  posi- 
tion between  these  two  extremes.  He  is  nowadays,  fortunately 
for  himself,  expected  to  be  a  producer ;  he  is  expected  to  be 
personally  familiar  with  investigation  and  investigators ;  he  is 
increasingly  involved  in  relations  with  the  secondary  schools,  and 
he  thus  becomes  acquainted  with  their  limitations  and  their 
needs.  Not  less  important  is  his  close  association  with  the  select 
body  of  advanced  students  with  whom  he  continually  discusses 
new  problems  as  they  arise ;  and  this  is  highly  advantageous  to 
all  concerned,  for  in  these  discussions  it  is  pretty  certain  that 
crudities  of  manner  or  matter  will  be  thrashed  out.  This  style 
of  treatment  is  not  found  in  any  other  part  of  the  round  of  atten- 
tions that  the  well-cared-for  subject  receives.  Discussions  in 
scientific  societies  where  expert  meets  expert  are  brief,  and  too 
often  insufficient  for  thorough  scrutiny.  They  truly  have  the 
advantage  of  being  as  a  rule  between  persons  of  what  would  be 
commonly  called  " equal  standing";  but  the  discussions  between 
a  professor  and  his  advanced  student,  carried  on  around  a  table 


NEED  OF  GEOGRAPHY  IN  THE  UNIVERSITY       163 

where  all  sit  on  chairs  of  the  same  height,  familiarly  gathering 
together  week  after  week,  are  by  no  means  always  unequal  con- 
tests. They  are  admirably  adapted  to  searching  out  the  strong 
and  weak  points  of  a  subject. 

The  product  of  university  discussion  is  a  body  of  seasoned  and 
tested  knowledge,  well  arranged  for  use.  The  knowledge  comes 
in  part  by  inheritance  from  earlier  years  ;  but  fresh  additions  are 
constantly  made  by  contemporary  experts,  by  the  professors 
themselves,  and  by  their  advanced  students.  The  seasoning  and 
testing  of  this  body  of  knowledge  is  peculiarly  the  function  of 
the  university  ;  a  study  that  is  unfortunate  enough  not  to  receive 
this  phase  of  attention  will  certainly  remain  in  a  backward  con- 
dition. No  other  treatment  that  a  subject  receives  can  replace 
the  attention  bestowed  upon  it  in  the  university.  The  recogni- 
tion of  geography  as  a  fitting  subject  for  higher  instruction  and 
investigation  must  therefore  not  only  result  in  improving  the 
education  of  those  whose  occupations  call  for  a  thorough  knowl- 
edge of  the  subject;  it  will  also  improve  the  condition  of  the 
subject  itself,  so  that  future  work  upon  it  can  be  done  both  by 
school-teacher  and  expert  to  greater  advantage. 

The  effect  of  a  better-ordered  condition  of  any  subject  as 
developed  by  university  presentation  and  discussion  is  especially 
apparent  in  secondary  schools.  Improvement  in  the  schools  is 
of  high  importance  not  only  because  it  reacts  favorably  on  all 
later  studies,  but  also  because  it  affects  a  greater  number  of 
persons  than  can  be  reached  anywhere  else  through  the  educa- 
tional system.  It  is  largely  for  these  reasons  that  the  university 
study  of  geography  seems  to  me  to  be  especially  important.  It 
will  not  only  serve  to  improve  the  condition  of  geography  in 
general  and  to  give  better  preparation  to  professional  geogra- 
phers of  all  kinds,  but  it  will  also  have  a  peculiarly  invigorating 
effect  on  the  fundamental  subject  of  geography  in  the  schools. 

The  progress  of  university  influence  on  geography  from  the 
higher  institutions  into  the  schools  will  be  easily  traced.  It  will 
be  from  among  those  students  who  specialize  in  geography  in 
the  universities  that  new  professorships  of  geography  will  be 
filled  in  the  colleges  and  professional  schools.  The  students  of 
geography  in  college  will  take  places  as  teachers  of  geography 


1 64  EDUCATIONAL  ESSAYS 

and  the  allied  subjects  in  high  schools  and  normal  schools.  The 
graduates  of  these  schools  will  carry  the  better  understanding 
that  they  have  gained  of  the  subject  down  into  the  grammar 
schools,  and  thus  at  last  the  subject  will  be  begun  aright  at  its 
beginning.  In  that  good  time  coming,  college  students  who  look 
forward  to  becoming  teachers  of  geography  in  high  and  normal 
schools  will  study  geology,  including  field  work,  along  with  their 
geography,  and  they  will  hereby  gain  a  sense  of  the  real  mean- 
ing of  geographical  facts.  Thus  equipped  they  will  carry  their 
pupils  much  farther  than  they  now  advance,  and  consequently 
such  of  the  high-school  pupils  as  look  forward  to  becoming 
teachers  in  the  grammar  schools  will  be  able  to  enter  their  work 
with  a  much  better  understanding  of  it  than  is  now  commonly 
possessed  by  school-teachers  of  that  grade.  Thus  guided  the 
young  scholars  will  find  their  native  intelligence  fully  exercised 
in  the  study  of  the  wonderfully  varied  facts  of  geographical  form 
and  distribution  and  in  the  understanding  of  the  interesting  cor- 
relations by  which  these  facts  are  associated  with  others.  This 
will  be  better  for  school  children  than  the  dulling  or  blunting  of 
their  intelligence  that  has  been  so  often  practiced  in  the  empir- 
ical study  of  a  rational  subject. 


IX 

PHYSICAL  GEOGRAPHY  AS  A  UNIVERSITY 
STUDY 

The  Logical  Method  in  Geography.  Success  in  the  study  of 
geography,  as  in  the  study  of  other  subjects,  depends  largely  on 
the  share  of  mental  light  with  which  the  facts  are  illuminated. 
For  example,  during  the  two  weeks  in  which  my  class  in  physical 
geography  has  recently  been  occupied  with  the  tides,  a  long  roll 
of  tracing  linen  has  been  hanging  on  the  laboratory  wall,  con- 
taining copies  of  a  half-month  of  tidal  curves  at  Honolulu,  Boston, 
Philadelphia,  Port  Townsend  (Oregon),  and  Point  Clear  on  the 
gulf  of  Mexico.  The  essential  facts  of  tidal  oscillation  are  thus 
exhibited  with  great  clearness.  While  these  curves  were  illumi- 
nated only  by  the  light  that  came  in  through  the  laboratory 
windows,  the  facts  were  but  imperfectly  perceived.  The  more 
peculiar  variations  of  the  curves  involved  in  the  diurnal  inequality 
of  tidal  amplitude  and  interval  could  not  be  discovered  by  eye- 
sight alone,  at  least  not  by  the  simple  eyesight  of  such  observers 
as  are  found  among  average  college  students  ;  but  during  the 
same  week  that  the  class  was  examining  these  tidal  tracings  in 
the  laboratory,  and  thereby  gaining  an  approach  to  a  simple 
inductive  knowledge  of  the  principal  facts  of  the  subject,  the 
problem  was  taken  up  from  the  other  side  in  lectures,  which  dis- 
cussed the  theoretical  consequences  of  the  interaction  of  two 
bodies,  and  deduced  from  the  theory  of  gravitation  a  number  of 
special  results  that  ought  to  occur  if  the  theory  of  the  tides  is 
correct.  As  an  aid  in  this  deductive  discussion  I  placed  three 
great  circles  of  paper  around  a  globe  so  as  to  represent  the 
theoretical  arrangement  of  tidal  deformation,  with  the  high-tide 
poles  and  the  low-tide  equator  and  their  relation  to  the  latitude 
circles  of  the  earth.  Now,  returning  to  the  tidal  diagrams  with 
the  results  of  the  tidal  theory  in  mind,  it  is  only  the  poorly 
trained,  the  dull,  or  the  stolid  student  who  feels  no  mental 

165 


1 66  EDUCATIONAL  ESSAYS 

satisfaction  in  the  successful  meeting  of  the  facts  of  observation 
and  the  consequences  of  theory.  Facts  before  noted,  but  not  un- 
derstood, now  gain  meaning ;  facts  before  disconnected  now  fall 
into  their  natural  relationships ;  facts  before  unnoticed  are  now 
searched  for  and  found,  and  wonder  is  even  excited  that  they 
were  not  seen  sooner.  Neither  induction  nor  deduction  alone 
satisfies  the  mind.  However  full  the  series  of  facts,  however 
extended  the  deductions  from  theory,  both  facts  and  deductions 
are  of  small  value  while  they  remain  unmated.  Properly  con- 
fronted, they  pair  off,  and  each  one  reacts  on  its  mate  most  favor- 
ably. If  the  facts  are  well  observed  and  recorded,  if  the  theory 
is  justly  based  and  logically  extended  to  its  consequences,  the 
inductions  and  deductions  mutually  complete  each  other,  and 
the  mind  is  satisfied.  The  window  light  then  seems  a  dull  illumi- 
nation of  the  tidal  tracings  compared  to  the  light  that  shines  on 
them  from  the  understanding. 

As  with  the  tides  of  the  ocean,  so  with  the  forms  of  the  land. 
They  are  but  half  seen  if  examined  only  by  daylight.  They  are 
.less  than  half  appreciated  if  seen  without  an  understanding  of 
the  generalizations  by  which  they  are  correlated.  The  more 
complete  the  mental  scheme  by  which  an  ideal  system  of  topo- 
graphical forms  is  rationally  explained,  the  more  clearly  can  the 
physical  eye  perceive  the  actual  features  of  the  land  surface 
and  the  more  definitely  can  it  record  them  in  mental  impressions. 
Topographical  forms  are  so  varied,  and  often  so  complicated,  that 
the  outer  eye  alone  is  no  more  competent  to  detect  all  their  intri- 
cacies and  correlations  than  it  is  to  discover  all  the  peculiarities 
of  the  tidal  curves.  It  is  true  that  with  exceptionally  keen 
powers  of  observation  and  with  unusual  opportunity  for  delib- 
erate examination,  the  unaided  eye  may  come  to  see  more  and 
more  of  the  ultimate  facts ;  but  these  conditions  are  so  rare  that 
they  need  not  be  considered.  The  average  eye  and  the  usual 
time  allowed  for  observation  do  not  suffice ;  they  must  be  sup- 
plemented by  the  quickened  insight  that  comes  from  rational 
understanding. 

No  better  confirmation  of  this  conclusion  can  be  found  than  in 
the  experience  of  those  who  have  to  employ  engineers  who  are 
untrained  in  geology  and  geography  to  make  topographical  maps. 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  167 

The  work  that  si.ch  surveyors  produce  is  rigid,  mechanical,  un- 
sympathetic, inaccurate,  inexpressive.  If  time  were  allowed 
them  to  run  out  all  their  contours  by  actual  measurement,  an 
exact  map  might  be  produced,  but  neither  time  nor  money 
can  be  devoted  to  so  slow  and  expensive  a  method.  Even  the 
best  surveys  are  necessarily  sketched  in  great  part,  and  the 
topographer  must  appreciate  his  subject  before  he  can  sketch  it. 
He  must  have  a  clear  insight  into  its  expression ;  his  outer  eye 
must  be  supplemented  by  his  inner  eye.  Then  he  can  make  up 
a  valuable,  even  though  not  an  expensive,  map.  I  do  not  mean 
for  a  moment  that  he  is  to  invent  and  not  to  observe ;  that  he  is 
to  make  a  fancy  picture  instead  of  a  true  likeness.  My  point  is 
simply  that  the  difficulty  of  making  a  true  likeness  is  so  great 
that  all  aids  toward  it  must  be  employed  ;  and  one  of  the  chief 
aids  to  sharp  outsight  is  clear  insight.  How  can  a  clear  geo- 
graphical insight  be  gained  ? 

An  analogy  with  the  study  of  the  tides  may  still  serve  us. 
The  facts  of  the  tides  are  first  presented  in  what  seems  like  a 
bewildering,  even  an  overwhelming,  variety,  without  suggestion 
of  order  or  meaning.  While  these  facts  are  studied  and  clas- 
sified, let  the  system  of  the  tides  be  deduced  in  accordance 
with  accepted  physical  laws.  Let  the  tidal  theory  be  followed 
far  enough  to  discover  consequences  so  numerous  and  so  intri- 
cate that  they  cannot  be  imitated  by  chance.  Neither  the  in- 
ductive nor  the  deductive  work  should  have  precedence.  They 
should  advance  together,  but  without  confusing  one  with  the 
other.  When  both  processes  are  well  advanced,  let  the  facts  be 
reexamined  in  the  light  of  the  theory,  and  summon  a  critical 
judgment  to  determine  how  far  the  reports  of  outsight  and 
insight  agree.  Success  in  such  study  requires  that  the  facts 
shall  have  been  closely  observed,  clearly  described,  and  fairly 
generalized,  the  inductive  results  thus  gained  being  held  apart 
by  themselves.  It  requires,  also,  that  the  theory  shall  have  been 
logically  extended  to  its  legitimate  consequences,  the  deductive 
results  thus  secured  being  stored  away  in  a  special  mental  com- 
partment. Then,  in  due  order,  bring  forth  the  corresponding 
members  of  the  two  classes  of  results  and  judge  of  the  success 
of  the  theory  by  the  agreements  thus  discovered. 


1 68  EDUCATIONAL  ESSAYS 

Let  the  same  method  be  applied  in  the  study  of  geography. 
Set  an  abundant  array  of  facts  before  the  class  in  the  laboratory. 
Let  the  facts  be  examined  and  classified  as  far  as  possible, 
simply  according  to  their  apparent  features' and  without  regard 
to  explanation.  At  the  same  time,  present  sin  outline  of  a  de- 
ductive geographical  system  in  the  lecture  /oom.  During  the 
advance  of  the  two  lines  of  work,  compare  their  results  fre- 
quently, but  do  not  confuse  them.  In  a  few  months  a  large 
array  of  facts  may  be  examined,  an  extended  deductive  system 
may  be  developed,  and  the  two  may  be  compared  in  the  most 
thorough  manner.  Every  comparison  aids  further  advance  in 
both  parts  of  the  work.  Both  outsight  and  insight  are  cultivated. 
A  geographical  understanding,  based  on  a  proper  combination  of 
many  mental  faculties,  is  aroused  and  strengthened.  The  real 
study  of  geography  is  well  begun.  The  several  steps  involved 
in  this  plan  of  work  may  now  be  traced  in  some  detail. 

Introductory  Illustration  of  Facts.  It  is  well  at  the  outset  to 
present  a  collection  of  varied  geographical  illustrations,  in  order 
to  bring  prominently  before  the  mind  the  great  variety  of  the 
facts  with  which  we  have  to  deal.  At  the  same  time  a  prelimi- 
nary exercise  is  gained  in  the  interpretation  of  different  means 
of  geographical  representation.  The  following  list  will  serve  to 
indicate  the  class  of  materials  from  which  selection  may  be 
made  for  a  first  week's  laboratory  work  : 

Heim's  model  of  an  Alpine  torrent ;  Harden's  model  of  Mor- 
rison's cove,  Pennsylvania,  or  a  photograph  of  this  model,  or 
of  Branner's  model  of  Arkansas  ;  Jackson's  photograph  of  the 
deep  valley  of  the  Blackwater  in  the  plateau  of  West  Virginia ; 
Holzel's  oleograph  of  the  Hungarian  plain  ;  Becker's  elaborately 
colored  and  shaded  relief  map  of  the  canton  Glarus,  Switzerland; 
a  group  of  contoured  map  sheets,  as  the  twelve  that  embrace 
the  Berkshire  plateau  and  the  Connecticut  valley  in  western 
Massachusetts,  or  the  nine  that  embrace  the  zigzag  ridges  north- 
east of  Harrisburg,  Pennsylvania,  mounted  as  a  wall  map  for  bet- 
ter convenience  in  study;  a  hachured  map,  such  as  that  of  the 
Scotch  Highlands,  in  a  group  of  sheets  of  the  British  Ordnance 
Survey,  also  mounted  as  a  wall  map ;  a  tinted  relief  map,  as  of 
New  Jersey,  from  the  topographical  atlas  of  that  state,  etc. 


GEOGRAPHY  AS  A  UNIVERSITY  STUJ  tf  169 

The  need  of  the  systematic  study  of  geography  is  apparent 
from  the  difficulty  that  most  students  have  in  expressing  the 
facts  portrayed  in  these  various  illustrations.  Words  are  not  easily 
summoned  to  describe  them.  Many  of  the  illustrations  are  on  a 
much  larger  scale  than  is  commonly  employed  in  atlases,  and  the 
ordinary  accounts  of  direction  and  distance,  usually  employed  in 
describing  similar  maps,  are  at  once  felt  to  be  insufficient  to  ex- 
press the  varied  reliefs  here  exhibited.  How  can  the  student 
best  approach  a  perception  and  an  understanding  of  the  facts 
before  him  and  at  the  same  time  gain  an  ability  to  describe  them 
in  fitting  language  ? 

Insufficiency  of  Inductive  Study.  The  ordinary  fund  of  geo- 
graphical terms  does  not  suffice  to  describe  good  maps  and  models 
with  sufficient  exactness.  Further  than  this,  a  few  questions 
from  the  instructor  will  show  that  many  facts  plainly  set  forth 
are  not  seen  at  all.  Interpretations  and  correlations  are  not  even 
suspected.  This  is  perfectly  natural  when  it  is  remembered  that 
most  college  students  have  never  been  taught  to  observe  closely 
or  to  express  themselves  clearly  in  well-chosen  words.  It  is  still 
more  natural  when  it  is  remembered  that  the  little  knowledge  of 
geography  that  they  have  brought  from  school  is  hardly  more 
than  a  confused  memory  of  an  unsystematic,  empirical  text-book. 
Whether  their  observation  is  directed  to  the  semblance  of  facts 
in  maps,  views,  and  models,  or  to  the  actual  facts  of  outdoor 
nature,  observation  is  attempted  only  with  the  outer  eye ;  the 
inner  eye  has  never  been  opened.  The  idea  that  all  the  forms 
of  the  land  are  systematically  developed  has  never  been  implanted 
in  their  minds.  They  possess  no  general  and  well-tested  deduct- 
ive understanding  of  the  development  of  land  forms,  no  system 
of  terrestrial  morphology.  The  facts  of  observation  excite  no 
harmonious  response  from  the  corresponding  members  of  a  de- 
ductive geographical  scheme. 

While  the  study  of  geography  remains  in  this  incomplete  and 
illogical  condition,  it  is  a  blind  study,  although  it  is  carried  on 
chiefly  through  the  eye.  While  the  life  of  the  features  of  the 
earth's  surface  is  not  perceived,  geography  is  a  dead  study. 
The  features  of  the  land  that  the  outer  eye  sees  will  awaken  no 
sufficient  sympathy  in  the  understanding  until  the  scientific 


170  EDUCATIONAL  ESSAYS 

imagination  has  deduced  a  whole  system  of  geography,  filled 
with  mental  pictures  of  all  kinds  of  forms  in  all  stages  of  develop- 
ment, among  which  the  report  from  the  outer  eye  may  find  its 
mate.  However  faithfully  mere  observation  is  carried  on,  the 
impression  on  the  retina  might  as  well  be  the  record  on  a  pho- 
tographic plate,  as  far  as  appreciative  insight  and  understanding 
are  concerned.  Let  us  therefore  strive  to  complete  a  deductive 
geographical  scheme,  even  as  we  strive  to  complete  our  deduct- 
ive tidal  scheme,  until  it  shall  at  last  be  ready  to  meet  not  only 
all  the  actual  variety  of  nature,  but  all  the  possible  variety  of 
nature.  Only  when  such  a  scheme  as  this  is  well  advanced  is  the 
student  ready  to  appreciate  the  materials  presented  in  the  labo- 
ratory work.  The  maps  and  models  shown  in  the  first  week  are 
therefore  repeatedly  introduced  with  others  in  the  systematic  ad- 
vance of  the  course,  and  the  student  may  gauge  his  progress  by  the 
increased  meaning  that  these  illustrations  gain  on  every  return. 

Let  us  next  consider  the  development  of  a  deductive  geograph- 
ical scheme,  by  which  external  observation  is  to  be  supplemented 
and  completed.  Let  it  be  understood  at  the  outset  that  to  ex- 
ceed the  variety  of  nature  is  an  extended  enterprise,  a  remote 
and  ideal  goal,  toward  which  we  strive.  Let  no  excessive  flight 
of  theory  carry  us  far  from  the  earth  and  overcome  us  in  mid- 
air. Let  us  carefully  guard  against  an  unwarranted  wandering 
of  the  imagination  by  frequent  conferences  with  the  facts  of 
observation,  hoping  to  return,  like  old  Antaeus,  strengthened  for 
new  efforts  after  every  touch  of  Mother  Earth. 

The  Deductive  Geographical  Scheme.  It  is  the  fundamental 
generalization  of  elementary  geology  to  note  that  the  lands  are 
wasting  away  under  the  destructive  attack  of  the  weather.  The 
hardest  rocks  decay ;  their  waste  creeps  and  washes  down  to 
lower  and  lower  levels,  never  satisfied  till  it  reaches  the  sea. 
However  broad  a  plateau,  however  lofty  a  mountain  range,  it 
must,  if  time  enough  be  allowed,  be  worn  down  to  sea-level  under 
the  weather  ;  and  the  unceasing  beat  of  the  sea  on  its  shores  must 
reduce  it  still  lower  to  a  submarine  platform.  Since  the  remote 
beginning  of  geological  time  there  has  been  time  enough  and 
plenty  to  spare  to  reduce  all  the  lands  to  such  a  submarine  plat- 
form ;  but  as  high  lands  still  exist,  it  must' be  concluded  that  they 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  171 

are  revived  from  time  to  time  and  from  place  to  place  by  some 
forces  antagonistic  to  those  of  sub-aerial  denudation.  In  whatever 
way  a  new  mass  is  offered  to  the  wasting  forces,  let  us  call  the  forces 
that  uplift  it  "  initial  forces,"  and  the  forms  thus  given  "  initial 
forms."  Let  all  the  forces  of  wasting  be  called  destructional 
forces  ;  let  the  sea-level  surface  —  down  to  which  a  sufficiently 
long  attack  of  the  destructional  forces  will  reduce  any  initial 
form  —  be  called  the  ultimate  base-level ;  and  let  the  portion  of 
geological  time  required  for  the  accomplishment  of  this  task  be 
called  a  physiographic  cycle.  Initial  forces,  destructive  forces, 
base-level,  and  cycle  are  our  primary  terms.  A  full  understand- 
ing of  the  destructional  processes  requires  deliberate  study  of 
mineralogy  and  lithology,  chemistry,  and  structural  geology ;  a 
good  understanding  of  initial  forces  and  processes  has  not  yet 
been  gained,  but  a  review  of  the  advance  made  towards  it  carries 
the  student  through  a  wide  range  of  geological  theories  in  which 
physics  and  mathematics  are  continually  appealed  to,  —  perhaps 
sometimes  with  too  great  a  confidence  in  the  applicability  of 
their  conclusions  concerning  an  ideal  earth  to  the  case  of  the 
actual  earth. 

If  the  cycle  of  destructive  development  is  not  interrupted,  any 
initial  form  will  pass  through  a  series  of  sequential  forms  and  will 
ultimately  be  reduced  to  a  monotonous  base-level  plain  of  denu- 
dation. This  is  a  broad  abstract  statement.  It  is  simply  the  first 
framework  of  the  geographical  scheme.  It  is  a  mere  sketch  in 
faint  outline,  needing  all  manner  of  finishing  before  its  full  mean- 
ing can  be  made  out.  It  must  be  filled  in  by  the  gradual  addition 
of  details.  The  first  step  involves  the  recognition  of  the  system- 
atic series  of  sequential  forms  produced  during  the  accomplish- 
ment of  the  destructive  work.  This  should  be  considered  before 
classifying  the  various  kinds  of  initial  forms  on  which  the  destruc- 
tional processes  begin  their  tasks.  Whatever  initial  form  exists 
at  the  beginning  of  the  cycle,  there  is  a  certain  general  succession 
of  sequential  features  common  to  nearly  all  cases  of  physiographic 
development.  The  understanding  of  this  succession  calls  for  the 
study  of  river  systems  and  the  general  drainage  of  the  land  under 
their  guidance,  because  it  is  so  largely  under  the  control  of  these 
processes  that  the  destructive  forces  do  their  work. 


172  EDUCATIONAL  ESSAYS 

Initial  Drainage.  At  the  beginning  of  a  cycle  there  are  rela- 
tively broad,  massive  forms  on  which  the  carving  of  the  destruc- 
tive forces  has  made  no  mark.  The  uncon  cent  rated  drainage,  or 
wet-weather  wash,  takes  its  way  down  the  steepest  slopes  of  the 
initial  surface,  until  the  supplies  from  either  side  meet  obliquely 
in  the  trough  lines,  forming  initial  streams  ;  these  unite,  forming 
initial  drainage'  systems.  If  the  trough  lines  are  systematically 
arranged,  as  among  the  corrugations  of  mountain  folds,  the  initial 
drainage  system  is  definitely  located;  if  the  trough  lines  are 
faintly  marked  and  lead  irregularly  about,  as  on  the  nearly  level 
surface  of  a  plateau,  the  drainage  is  essentially  vague  and  unsys- 
tematic. If  the  general  descent  of  the  trough  lines  is  here  and 
there  reversed  into  ascent,  lakes  are  accumulated  in  the  basins 
thus  determined  ;  and  this  is  very  common.  If  the  descent  of  the 
trough  lines  is  locally  intensified,  initial  falls  or  rapids  are  devel- 
oped ;  but  this  is  relatively  rare. 

Consequent  Drainage.  The  initial  streams  run  down  their 
troughs,  carrying  along  the  waste  that  is  washed  into  them,  and 
trenching  channels  beneath  the  initial  surface,  or  filling  initial 
hollows  ;  that  is,  degrading  or  aggrading  their  course,  as  the  ne- 
cessities demand.  As  soon  as  they  thus  depart  from  their  initial 
arrangement,  they  may  be  called  consequent  streams.  It  is  true 
that  the  initial  phase  of  a  drainage  system  endures  only  a  mo- 
ment ;  yet  it  seems  advisable  to  recognize  this  phase  by  employing 
a  special  name  for  it  before  introducing  the  term  "  consequent," 
which  indicates  the  much  longer  phase  that  next  follows.  As  long 
as  a  stream  flows  on  a  line  that  is  essentially  the  perpetuation  of  its 
initial  course,  it  may  be  called  a  consequent  stream  ;  the  trench 
that  it  cuts  and  the  valley  that  is  formed  by  the  widening  of  the 
trench  may  be  included  under  the  name  "  consequent  valley." 
Initial  features  are  encroached  upon  as  the  consequent  features 
make  their  appearance.  An  initial  lake  decreases  in  size  by  filling 
at  the  inlet  and  cutting  down  at  the  outlet ;  while  thus  dwind- 
ling away  it  is  a  consequent  lake.  A  fall  or  cascade  recedes 
from  its  initial  position,  but  as  long  as  it  endures  it  is  a  conse- 
quent fall. 

Subsequent  Drainage  Features.  As  the  consequent  streams 
deepen  their  valleys  beneath  the  initial  surface,  it  often  happens 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  173 

that  they  discover  structures  of  unequal  hardness.  If,  in  passing 
downstream,  a  weak  structure  succeeds  a  hard  structure,  the 
valley  will  be  quickly  deepened  in  the  former  and  slowly  in  the 
latter ;  a  local  increase  of  slope  appears  and  a  fall  or  cascade  is 
the  result.  This  is  a  subsequent  fall  on  a  consequent  stream. 
It  endures  until  the  harder  structure  is  worn  down  or  back  so 
far  that  it  overtakes  the  deepening  of  the  stream  bed  below  the 
fall.  The  extinction  of  falls  is  accomplished  in  adolescence  on 
large  streams  and  on  tilted  rocks,  but  it  may  not  be  reached  until 
maturity  on  the  smaller  streams  in  regions  of  horizontal  strata. 

A  further  consequence  of  the  discovery  of  the  variable  resist- 
ance of  internal  structure  is  the  variable  rate  at  which  the  narrow 
young  consequent  valley  widens  into  the  more  mature  open  valley. 
If  the  consequent  stream  crosses  a  local  transverse  belt  of  hard 
rocks,  the  gorge-like  form  of  the  valley  walls  may  there  be  re- 
tained into  the  maturity  of  the  region  as  a  whole.  If  it  crosses 
a  belt  of  weak  rocks,  the  consequent  valley  may  there  widen  so 
greatly  as  to  develop  other  valleys  on  either  side  of  its  path. 
Thus  many  a  transverse  consequent  stream,  cutting  its  valleys 
across  belts  of  harder  and  softer  structures,  allows  the  develop- 
ment of  longitudinal  valleys  on  every  belt  of  weak  structure  that 
it  traverses,  while  the  intermediate  belts  of  harder  structure 
stand  up  as  longitudinal  dividing  ridges.  The  longitudinal  stream's 
and  valleys  are  then  called  subsequent  branches  of  the  transverse 
consequent  streams  and  valleys.  Each  of  the  subsequent  streams 
deepens  its  valley  only  as  fast  as  the  downstream  deepening  of 
the  consequent  valley  permits. 

It  is  extremely  important  to  recognize  the  difference  thus 
indicated  between  consequent  and  subsequent  streams.  The 
first  control  the  drainage  of  a  region  in  its  early  stages  of  develop- 
ment. The  second  are  of  increasing  importance  in  the  secondary 
and  later  stages  of  growth,  when  they  share  the  drainage  of  the 
region  with  the  surviving  consequent  streams.  Subsequent  falls 
frequently  appear  on  consequent  streams,  but  they  are  rare  on 
subsequent  streams. 

It  is  manifest  that  the  development  of  subsequent  streams  will 
progress  to  the  greatest  extent  in  regions  of  disordered  and  com- 
plicated structure,  in  which  the  attitude  of  the  rocks  is  varied, 


174  EDUCATIONAL  ESSAYS 

and  in  which  contrasts  of  hardness  are  well  marked.  Such  is  the 
case  in  mountainous  regions.  On  the  other  hand,  regions  of  hori- 
zontal structure  have  no  normal  subsequent  streams.  All  the 
branch  streams  are  either  perpetuated  consequent  streams,  or 
else  they  are  developed  under  accidental  controls,  of  which  no 
definite  account  can  be  given.  It  is  to  these  self-guided  streams 
that  I  have  applied  the  term  "  insequent." 

Divides.  The  initial  divides  waste  slowly  and  become  conse- 
quent divides.  They  are  well  defined  in  a  region  of  distinct  initial 
relief ;  they  are  vague  or  practically  absent  on  the  even  surface 
of  young  plains  where  the  drainage  areas  are  really  undivided. 
As  subsequent  streams  develop,  especially  in  regions  of  tilted 
structure,  they  frequently  split  a  consequent  divide  and  make 
two  subsequent  divides,  between  which  lies  the  growing  subse- 
quent valley.  As  the  subsequent  divides  are  split  farther  and 
farther  apart,  lateral  subsequent  streams  are  developed  down  the 
internal  slopes  of  the  subsequent  valley,  and  these  are  in  head- 
water opposition  to  the  lateral  streams  on  the  diminishing  slopes 
of  the  adjacent  consequent  valleys.  During  changes  thus  pro- 
duced in  the  position  of  divides,  they  migrate  by  slow  creeping 
as  long  as  the  competing  streams  are  in  headwater  opposition; 
but  if,  as  sometimes  happens,  the  head  of  an  encroaching  subse- 
quent stream  pushes  its  divide  back  until  it  cuts  into  the  side  of 
a  consequent  stream,  then  the  divide  leaps  around  the  consequent 
headwaters  above  the  point  of  capture,  and  a  considerable  area 
that  had  been  tributary  to  the  captured  stream  is  suddenly  trans- 
ferred to  the  capturing  stream. 

A  limit  of  these  rearrangements  is  gradually  approached.  The 
persistent  consequent  streams  and  the  successful  subsequent 
streams  come  to  an  understanding  about  their  drainage  areas. 
The  divides  as  well  as  the  streams  are  then  maturely  adjusted  to 
the  structures  on  which  they  are  developed,  and  thenceforward 
further  change  is  slow. 

Stream  Profiles.  Let  us  next  examine  the  changes  produced 
in  the  initial  profile  of  the  troughs  where  the  first  streams  settled. 
The  irregularities  of  the  initial  profile  which  determine  lakes  and 
falls  are  in  most  cases  soon  extinguished.  The  profile  of  a  con- 
sequent stream  may  for  a  time  possess  unequal  slopes  at  its 


t 

GEOGRAPHY  AS  A  UNIVERSITY  STUDY  175 

subsequent  falls,  but  it  soon  attains  a  tolerably  systematic  curve 
of  descent,  steeper  near  the  headwaters,  flatter  near  the  mouth. 
While  the  young  stream  has  abundant  fall  and  rapid  current, 
with  moderate  load  delivered  from  the  relatively  simple  initial 
and  consequent  slopes  of  its  basin,  it  deepens  its  trench  rapidly. 
But  as  the  profile  becomes  flatter  and  the  current  runs  slower, 
and  as  the  area  of  wasting  slopes  increases  by  the  deepening  of 
the  consequent  valleys  and  the  development  of  subsequent 
valleys,  a  time  will  soon  arrive  when  the  carrying  power  is 
reduced  to  equality  with  the  load  ;  and  from  this  time  on  the 
deepening  of  the  valley  is  very  much  slower  than  before.  It  is 
only  as  the  load  from  the  wasting  slopes  decreases  in  amount 
that  the  deepening  can  go  on.  Following  certain  French  writers, 
the  profile  of  the  stream  when  this  balanced  condition  is  reached 
has  been  called  the  "profile  of  equilibrium."  The  term  is  incon- 
veniently long,  but  the  idea  is  of  essential  importance.  Mr. 
Gilbert  has  recently  suggested  to  me  that  a  stream  in  this  con- 
dition of  balance  between  degrading  and  aggrading  might  be 
called  a  "graded  stream,"  and  its  slope  a  "graded  slope." 

It  is  sometimes  said  that  streams  in  this  condition  have  reached 
base-level ;  but  this  introduces  a  confusion  of  ideas  that  should 
be  avoided.  For  example,  given  two  initial  areas  of  similar  form 
and  altitude  and  under  equivalent  climatic  conditions,  let  one 
be  made  of  resistant  rocks  and  the  other  of  weak  rocks.  The 
base-level  is  the  same  for  both.  The  streams  will  cut  deep 
into  the  harder  mass,  producing  strong  relief  before  reaching  a 
graded  profile,  because  its  waste  is  shed  so  slowly  that  the 
streams  can  carry  it  on  a  faint  slope.  They  can  cut  only  shallow 
valleys  in  the  weaker  mass,  for  its  waste  will  be  shed  so  rapidly 
that  a  steep  slope  is  needed  by  the  streams  to  carry  the  waste 
away.  The  contrast  between  the  two  areas  is  strengthened  if  the 
region  of  harder  structure  has  a  plentiful  rainfall  and  the  region 
of  weaker  structure  has  a  light  rainfall.  All  of  these  points  of 
difference  are  with  difficulty  stated,  if  the  streams  are  said  to 
have  reached  base-level  when  their  carrying  power  is  reduced  to 
equality  with  their  load. 

In  certain  cases  it  seems  to  be  possible  for  a  stream  to  cut 
down  its  profile  to  a  gentler  grade  in  its  early  adolescence  than 


I  ;6  EDUCATIONAL  ESSAYS 

is  suitable  to  later  adolescence  and  maturity.  If  we  conceive 
that  the  load  offered  by  the  waste  from  the  valley  slopes  con- 
tinues to  increase  after  the  grading  of  the  stream  has  been 
reached,  then  the  grade  must  be  steepened  again  by  the  deposi- 
tion of  the  excess  of  load,  thus  increasing  carrying  power,  and 
decreasing  load  and  maintaining  an  equilibrium.  Local  examples 
of  this  relation  are  often  seen  in  valleys  among  mountains,  where 
a  lateral  stream  is  depositing  an  alluvial  fan  in  the  larger  valley 
that  it  enters.  The  larger  valley  was  deepened  before  the  lateral 
valley  had  gained  a  considerable  area  of  wasting  slopes ;  but  as 
the  lateral  valley  grows  headwards  and  discharges  an  increasing 
volume  of  waste,  it  cannot  all  be  carried  by  the  main  stream, 
and  hence  the  main  valley  is  clogged  up,  and  its  grade  is  some- 
what increased. 

Stages  in  the  Cycle  of  Geographical  Development.  Following 
the  terminology  of  organic  growth,  it  is  convenient  to  speak  of  the 
successive  stages  in  the  physiographic  cycle  as  infancy,  youth, 
adolescence,  maturity,  old  age,  and  perhaps  second  childhood. 
Let  us  consider  particularly  the  activities  of  the  drainage  system 
as  determined  by  the  topographical  form  of  a  region  in  its  differ- 
ent stages. 

In  infancy  the  rainfall  is  slowly  concentrated  from  the  broad 
initial  surface ;  it  is  only  gradually  collected  into  streams ;  it  is 
often  delayed  in  lakes.  Much  of  it  is  lost  by  evaporation,  and 
the  ratio  of  discharge  at  the  river  mouth  to  rainfall  over  the 
river  basin  is  relatively  low.  The  initial  streams  simply  adopt 
the  courses  offered  to  them,  without  the  least  consideration  or 
foresight  regarding  the  difficulties  that  these  courses  may  involve 
in  the  process  of  valley  trenching.  The  load  that  they  have  to 
carry  is  relatively  light,  being  only  the  waste  that  creeps  and 
washes  down  the  broad  initial  slopes  under  the  guidance  of  the 
unconcentrated  drainage. 

In  youth  and  adolescence  the  drainage  lines  are  increased  in 
number  and  greatly  improved  in  their  ability  to  gather  and  dis- 
charge the  rainfall  quickly.  Numerous  little  trenches  are  incised 
in  the  broad  initial  surface,  and  the  distance  that  the  land  waste 
washes  and  creeps  under  the  guidance  of  unconcentrated  drain- 
age is  much  lessened  ;  delay  in  lakes  is  decreased ;  the  steep 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  177 

lateral  slopes  of  the  young  consequent  valleys  furnish  an  increas- 
ing amount  of  load  to  the  streams,  although  they  still  as  a  rule 
have  carrying  power  to  spare  in  their  impetuous  currents.  A 
good  beginning  is  made  in  the  search  for  the  best  location  of 
subsequent  streams.  As  the  subsequent  streams  become  better 
developed  in  later  adolescence,  the  original,  broad  initial  forms 
are  minutely  carved,  many  subsequent  divides  are  established, 
the  discharge  of  rainfall  is  very  prompt,  and  the  load  of  waste 
that  the  streams  have  to  carry  is  notably  increased. 

In  maturity  the  relief  retains  much  of  the  intensity  of  adoles- 
cence and  adds  thereto  a  great  variety  of  features.  The  valley 
lines  are  closely  adjusted  to  the  structure  of  the  region,  this 
condition  having  been  gained  by  a  delicate  and  thorough  process 
of  natural  selection,  in  which  the  most  suitable  drainage  lines 
survive,  and  the  less  suitable  ones  are  shortened  or  extinguished. 
The  impetuosity  of  youth  has  disappeared  ;  all  the  larger  streams 
have  developed  grades  on  which  their  ability  to  do  work  is  nicely 
adjusted  to  the  work  that  they  have  to  do ;  the  lower  courses 
already  show  signs  of  age,  while  the  upper  twig-like  branches 
are  relatively  youthful.  The  whole  drainage  system  is  earnestly 
at  work  in  its  task  of  base-leveling  the  region,  and  the  forms  that 
the  region  has  assumed  bear  witness  to  the  close  search  made 
by  the  streams  for  every  available  line  of  effective  work. 

From  this  time  onward  there  is  a  general  fading  away  of 
strength  and  variety,  both  of  forms  and  activities.  The  deepen- 
ing of  the  valleys  progresses  even  more  slowly  than  the  slow 
wasting  away  of  the  hilltops  ;  the  relief  fades  ;  the  load  offered 
to  the  stream  lessens.  The  rainfall  slowly  decreases  as  a  normal 
consequence  of  decrease  of  altitude ;  the  ratio  of  river  discharge 
to  rainfall  decreases  ;  the  small  headwater  branches  shorten  and 
dwindle  away ;  the  close  adjustment  of  stream  to  structure  is 
more  or  less  lost,  especially  by  the  larger  rivers,  which  meander 
and  wander  somewhat  freely  over  the  peneplain  of  denudation. 
Extreme  old  age  or  second  childhood  is,  like  first  childhood, 
characterized  by  imperfect  work  ;  activities  that  were  undeveloped 
in  the  earlier  stage  have  been  lost  in  the  later  stage. 

All  this  should  be  so  carefully  imagined  and  so  frequently 
reviewed  that  the  orderly  sequence  of  changes  may  pass  easily 


1 78  EDUCATIONAL  ESSAYS 

before  the  mind.  The  mind  should  come  to  be  in  so  close  a 
sympathy  with  the  progress  of  the  cycle  as  to  forget  human 
measures  of  time  and  catch  instead  the  rhythm  of  geographical 
development,  even  to  the  point  of  almost  wishing  to  hurry  to 
one  place  or  another  where  some  change  of  drainage  or  of  form 
is  imminent  for  fear  of  failing  to  be  in  time  to  see  it  in  its 
present  stage. 

Shore-Lines.  While  the  sub-aerial  forces  are  denuding  the 
surface  of  the  land,  the  waves  are  beating  on  the  shore  and  re- 
ducing the  land  mass  to  a  submarine  platform.  They  begin  their 
work  on  a  level  line,  contouring  around  the  slope  of  the  land 
mass  as  it  is  offered  to  them.  The  contour  is  simple  if  the  sea 
lies  on  a  rising  sea-bottom,  evenly  spread  over  with  sedimentary 
deposits  ;  the  contour  is  irregular  if  the  sea  lies  on  a  depressed 
land,  more  or  less  roughened  by  previous  denudation.  The  waves 
of  a  great  ocean  work  rapidly  on  a  leeward  shore,  especially  if 
it  has  a  steep  slope  and  if  its  rocks  are  not  too  hard ;  but  if  the 
descent  to  deeper  water  is  very  gradual,  the  waves  may  for  a  time 
spend  their  force  chiefly  on  the  bottom,  building  offshore  bars 
with  the  material  they  gather  up,  and  thus  deepening  the  water 
outside  of  the  bars  for  a  better  attack  on  the  land  later  on.  The 
shore-line  is  generally  simplified  as  the  attack  advances,  but  it 
may  for  a  time  become  more  irregular  if  the  waves  are  strong 
and  the  land  structure  is  of  diverse  resistances.  Its  changes 
deserve  as  careful  an  analysis  as  is  given  to  the  forms  of  the 
land,  but  they  cannot  be  traced  here  for  lack  of  space. 

Illustrations  of  the  Deductive  Scheme.  However  much  the 
advance  of  a  deductive  scheme  of  study  may  be  aided  by  refer- 
ence to  concrete  illustrations  during  its  progress,  its  statement 
.should  be  abstract,  in  order  to  emphasize  the  essentially  deduct- 
ive side  of  the  study.  It  is  difficult  to  follow  such  a  method 
without  artificial  aids.  Hence,  in  discussing  the  theory  of  the 
tides,  a  model  of  certain  theoretical  tidal  circles  was  introduced 
for  the  convenience  of  definition  and  argument.  It  was  found 
to  be  an  effective  aid  in  reaching  certain  geometrical  conse- 
quences that  follow  from  the  rotation  of  the  earth  on  an  axis  that 
is  not  coincident  with  the  axis  of  the  tidal  circles.  This  model 
was  an  illustration  of  the  same  order  as  the  diagrams  employed 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  179 

in  text-books  on  geometry.  In  the  same  way  a  series  of  some 
thirty  rough  paper  reliefs,  constructed  several  years  ago  to  illus- 
trate a  course  of  lectures  to  teachers,  under  the  auspices  of  the 
Boston  Society  of  Natural  History,  are  introduced  to  aid  in 
giving  clearness  to  the  conception  of  the  geographical  scheme. 
They  are  roughly  made,  hardly  better  than  blackboard  diagrams, 
except  in  having  three  dimensions,  yet  they  certainly  serve  a 
good  purpose  as  aids  in  following  deductive  statements.  Being 
two  or  three  feet  in  length  and  yet  light  enough  to  handle  easily, 
they  are  frequently  brought  into  the  lecture  room,  although  they 
are  used  chiefly  in  the  laboratory,  where  they  can  be  examined 
and  described  deliberately.  Nearly  all  the  points  thus  far  men- 
tioned are  illustrated  in  one  way  or  another  by  these  models, 
but  I  can  here  give  account  of  only  a  few  of  them. 

While  occupied  with  the  first  considerations  of  the  cycle  and 
its  systematic  variations  of  relief,  both  in  intensity  and  variety, 
use  is  made  of  three  simple  models,  which  are  -found  to  be  of 
particular  value  in  fixing  the  fundamental  ideas.  The  first  shows 
a  broad  upland,  traversed  by  a  main  river  with  a  few  branching 
streams,  all  in  valleys  of  the  canon  type.  The  form  of  the 
second  is  well  diversified,  there  being  about  as  much  of  lowland 
in  its  wide-open  valleys  as  there  is  of  upland  on  its  well-separated 
hills.  The  third  is  a  broad  lowland  for  the  most  part,  but  low 
hills  rise  above  the  general  level  near  the  headwaters  of  the 
streams.  The  main  river  has  essentially  the  same  course  in  all 
three  models,  and  there  is  a  manifest  relation  in  the  position  of 
the  streams  and  inter-stream  hills  of  the  series,  plainly  showing 
genetic  relationship.  The  three  models  are  different  forms  of 
the  same  region  at  certain  stages  in  its  cycle  of  development. 
Exercises  are  held  in  the  simple  description  of  these  forms,  and 
of  other  forms  that  might  be  interpolated  in  the  series.  It  is 
suggested  that  the  duration  of  a  cycle  should  be  divided  into  a 
hundred  equal  parts,  and  that  the  stages  occupied  by  the  three 
models  should  be  designated  by  appropriate  numbers.  After 
some  discussion  it  is  agreed  that  they  may  be  represented  by  five, 
twenty,  and  forty,  thus  impressing  the  idea  that  maturity  is 
reached  long  before  middle  life,  and  that  the  passage  through 
old  age  is  extremely  slow  compared  to  the  advance  from  youth 


l8o  EDUCATIONAL  ESSAYS 

well  into  maturity.  These  exercises  are  accompanied  by  others, 
in  which  illustrations  of  actual  geographical  forms  are  presented, 
as  will  be  explained  later  ;  but  it  is  important  that  the  different 
character  of  the  two  should  be  clearly  kept  before  the  mind. 

Complications  of  the  Simple  Scheme.  The  difficulty  of  finding 
examples  of  actual  forms  in  the  various  stages  of  development 
of  a  single  cycle  suggests  that  the  departures  from  the  ideal  un- 
interrupted cycle  should  be  examined.  These  are  of  two  kinds, 
which  I  am  accustomed  to  call  "  accidents  "  and  "  interruptions." 
Such  departures  as  do  not  involve  a  change  in  the  attitude  of  a 
land  mass  with  respect  to  its  base-level  may  be  classed  under 
the  first  heading  as  accidents  ;  those  which  do  involve  a  change 
with  respect  to  base-level  will  fall  under  the  second  heading  as 
interruptions. 

The  most  important  accidents  are  climatic  and  volcanic. 
Climatic  accidents  include  changes  from  humid  to  arid,  and  from 
cooler  to  warmer  conditions,  independent  of  the  normal  climatic 
change  due  to  loss  of  relief  from  youth  to  old  age.  A  study  of 
such  a  region  as  the  Great  Salt  Lake  basin,  or  as  the  glaciated 
district  of  northeastern  America,  assures  us  that  these  accidents 
may  succeed  each  other  rapidly,  —  very  rapidly  compared  to  the 
rate  of  normal  climatic  change  dependent  on  loss  of  relief  from 
a  deformational  beginning  to  a  destructional  end.  Volcanic 
accidents  include  the  building  of  cones  and  the  outpouring  of 
lava  flows.  Both  the  glacial  and  the  volcanic  accidents  may 
occur  at  any  stage  of  a  cycle.  They  both  in  a  way  involve  con- 
structional processes  ;  both  may  be  regarded  as  furnishing  ex- 
amples of  new  initial  forms  ;  but  when  looked  at  with  respect 
to  the  surface  on  which  these  accidents  are  imposed,  and  with 
respect  to  the  relatively  brief  endurance  of  the  effects  of  the 
accidents,  they  are  seen  in  their  relatively  subordinate  character. 
When  sheets  of  drift  are  heavily  spread  over  a  country  of  low 
relief,  or  when  heavy  lava  floods  cover  and  bury  some  antecedent 
topography,  the  accidents  assume  such  proportions  that  they 
may  be  considered  as  revolutions,  after  which  a  new  start  is 
made  in  the  processes  of  denudation. 

A  cycle  is  interrupted  when  the  land  mass  rises  or  sinks, 
or  when  it  is  warped,  twisted,  or  broken.  Like  accidents, 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  181 

interruptions  may  happen  at  any  stage  of  development.  It  is  then 
convenient  to  say  that  the  sequential  form  attained  in  the  first 
incomplete  cycle  shall  be  called  the  initial  form  of  the  new  cycle, 
into  which  the  region  enters,  more  or  less  tilted  or  deformed 
from  its  former  shape.  Assuming  for  the  moment  that  the  in- 
terrupting process  is  so  rapid  that  its  duration  may  be  neglected, 
it  follows  that  in  cases  of  simple  vertical  movement,  up  or  down, 
the  rivers  and  streams  at  once  proceed  to  adapt  their  activities 
to  the  new  conditions.  They  are  shortened  and  betrunked  if 
the  interruption  is  a  depression  ;  they  are  revived  and  extended 
if  the  interruption  is  an  elevation.  These  two  special  conditions 
are  illustrated  by  paper  models.  One  model  exhibits  a  rolling 
country,  into  which  a  branching  bay  enters,  a  stream  descend- 
ing into  the  head  of  every  branch  of  the  bay.  No  flats  occur  at 
the  heads  of  the  bays  ;  no  cliffs  are  seen  on  the  headlands. 
Hence  it  is  said  that  on  reaching  maturity  this  country  was  de- 
pressed, and  that  the  depression  Occurred  very  recently.  The 
numerical  expression  of  this  example  would  be  20,  — ,  o ;  the 
minus  sign  not  indicating  subtraction,  but  merely  signifying  de- 
pression, and  the  zero  indicating  that  no  advance  has  been  yet 
made  in  the  new  cycle.  Another  model  exhibits  a  broad,  gently 
undulating  upland,  traversed  by  a  very  narrow  canon.  This  is 
interpreted  to  signify  that  an  elevation  occurred  in  the  old  age 
of  the  region,  and  that  since  then  the  streams  have  simply  en- 
tered a  new  youth,  incising  young  valleys  in  the  uplifted  pene- 
plain. The  formula  of  this  example  would  be  60,  +,  3.  Examples 
involving  deformation  of  a  land  surface,  and  the  accompanying 
possibility  of  antecedent  streams,  are  more  complicated  and 
cannot  be  here  introduced. 

It  is  convenient  to  use  the  term  "  episode,"  for  slight  interrup- 
tions, so  as  to  express  their  relative  unimportance.  I  have  also 
attempted  the  use  of  the  term  "  chapter  "  for  an  unfinished  cycle  ; 
but  in  talking  with  students  this  specialization  of  terms  hardly 
seems  necessary.  Any  region  whose  surface  has  been  developed 
partly  in  relation  to  one  base-level  and  partly  in  relation  to 
another, — that  is,  any  form  whose  development  has  involved 
two  or  more  incomplete  cycles,  —  is  said  to  have  a  composite 
topography.  Many  examples  of  such  forms  are  encountered. 


1 82  EDUCATIONAL  ESSAYS 

Special  Features  of  Second  or  Later  Cycles.  It  is  interesting 
to  notice  that,  in  certain  cases,  the  adolescent  stages  of  a  second 
or  later  cycle,  following  the  elevation  of  a  region  well  advanced 
in  a  previous  cycle,  present  features  that  did  not  characterize 
its  first  adolescence.  One  case  of  this  kind  is  seen  in  meander- 
ing river  gorges.  Young  rivers  in  their  first  cycle  may  cut 
crooked  gorges,  but  they  then  follow  consequent  courses,  and 
these  cannot  manifest  the  close  relation  between  volume  and 
radius  of  curvature  that  is  seen  in  true  meanders.  This  relation 
is  found  only  in  oldish  rivers,  which  develop  systematic  meanders 
on  their  own  flood  plains.  But  if  the  region  on  which  these 
rivers  flow  is  introduced  into  a  new  cycle  by  uniform  elevation, 
the  rivers  may  cut  down  their  meandering  channels  and  pro- 
duce meandering  gorges.  The  Osage  in  Missouri,  the  north 
branch  of  the  Susquehanna  in  Pennsylvania,  the  Seine  in 
northwestern  France,  and  the  Moselle  in  western  Germany 
may  be  cited  in  illustration  of  this  kind  of  occurrence. 

Another  case  in  which  a  second  adolescence  is  unlike  the  first 
is  found  in  regions  of  tilted  structure,  where  the  strata  is  of 
diverse  resistance,  thus  giving  good  opportunity  for  the  develop- 
ment of  subsequent  streams.  In  the  beginning  of  the  first  cycle 
there  are  no  subsequent  streams.  All  the  drainage  is  initial, 
antecedent  streams  not  being  now  considered.  In  adolescence 
the  drainage  is  chiefly  consequent,  although  subsequent  side 
streams  are  then  beginning  to  bud  forth  from  the  consequent 
streams.  In  past-mature  stages  the  subsequent  streams  may 
have  acquired  a  considerable  part  of  the  drainage  area.  Now, 
if  a  region  of  this  kind,  with  consequent  and  subsequent  drain- 
age, is  bodily  elevated,  all  the  streams  are  revived ;  they  all  cut 
down  new  trenches  toward  the  new  base-level.  But  in  this  case 
the  revived  subsequent  streams  begin  the  new  work  at  the  same 
time  as  the  revived  consequent  streams,  and  they  will  go  on 
rapidly  in  acquiring  still  more  drainage  area.  Therefore,  in  the 
adolescence  or  maturity  of  the  second  cycle,  the  drainage  area 
acquired  by  the  subsequent  streams  will  be  proportionately  large 
—  much  larger  than  at  the  same  stage  of  the  first  cycle.  Much 
faith  may  be  placed  in  this  deduction.  If  the  drainage  of  an 
adolescent  region  is  largely  subsequent,  and  but  little  consequent, 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  183 

the  region  may  be  regarded  as  almost  certainly  in  a  second  cycle 
of  development,  after  a  first  cycle  of  well-advanced  age. 

Illustrative  Material.  One  of  the  greatest  difficulties  in  the 
way  of  teaching  physical  geography  arises  from  the  failure  of 
the  student  to  know  what  the  teacher  is  talking  about.  The 
teacher  may  have  traveled  and  observed  extensively  ;  a  large 
variety  of  geographical  forms  are  in  his  memory,  ready  to  be 
summoned  by  name  when  picturing  the  stages  of  the  deductive 
scheme ;  but  no  amount  of  description  suffices  to  place  these 
mental  pictures  before  the  class.  The  best  means  of  overcoming 
this  difficulty  is  found  in  the  use  of  the  projecting  lantern  ;  and 
now  that  the  electric  light  may  be  used  in  projecting  slides  on 
the  screen,  and  the  room  kept  light  enough  for  the  class  to  take 
notes  while  the  pictures  are  exhibited  and  explained,  the  only 
thing  left  to  be  desired  is  a  good  series  of  views,  carefully  se- 
lected to  present  typical  examples  of  land  forms  in  various  stages 
of  more  or  less  complicated  development.  These  views  are  not 
intended  primarily  to  furnish  localized  examples  of  geographical 
forms,  although,  of  course,  they  have  much  value  in  that  direc- 
tion. Their  greater  value  comes  from  the  vividness  of  the  con- 
ceptions by  which  the  different  kinds  of  forms  and  different 
stages  of  development  of  the  deductive  scheme  are  held  in  the 
mind.  The  collection  of  slides  that  I  now  use  includes  a  large 
variety  of  views ;  although  very  useful,  it  is  still  imperfect.  It 
should  be  extended  by  the  addition  of  many  views  taken  expressly 
to  meet  its  needs,  for  the  photographs  and  slides  commonly  to 
be  had  of  dealers  are  as  a  rule  taken  with  anything  but  geograph- 
ical intention.  As  an  indication  of  the  character  of  illustrations 
used  in  a  single  lecture,  I  may  mention  the  following  examples 
and  add  an  outline  of  the  comments  made  on  them. 

When  the  general  idea  of  a  geographical  cycle  has  been  pre- 
sented, including  the  initial  forms  with  which  it  opens  and  an 
outline  of  the  destructional  forms  by  which  its  development  is 
characterized,  the  next  lecture  may  be  devoted  almost  entirely 
to  illustrations.  First,  a  few  slides  to  show  various  initial  forms. 
Muir's  Butte,  a  young  volcanic  cone  in  California,  introduces  a 
series ;  it  is  practically  unworn.  Its  growth  was  so  rapid  and 
so  recent  that  no  significant  advance  in  its  denudation  has  yet 


1 84  EDUCATIONAL  ESSAYS 

been  accomplished.  Mt.  St.  Elias  comes  second  ;  as  described 
by  Russell,  it  is  an  initial  form  slightly  altered  ;  an  essentially 
young  mountain  mass.  The  considerable  time  required  for  ac- 
complishment of  so  great  an  initial  uplift  may  have  been  enough 
for  the  slight  dissection  already  seen  on  its  surface.  While  the 
building  of  a  volcanic  cone  is  spasmodic,  almost  instantaneous, 
the  uplift  of  a  great  mountain  is  rather  slow ;  its  uplift  is  brief 
only  when  compared  to  the  duration  of  the  destructive  cycle  on 
which  it  thereby  enters.  When  first  describing  the  cycle,  it  was 
implied  that  the  destructive  forces  make  no  beginning  until  the 
initial  forces  have  completed  their  work.  The  view  of  Mt.  St. 
Elias  corrects  that  false  idea.  Several  plains  follow,  —  all  dead 
level ;  all  ending  in  even  sky  lines  :  the  Llano  Estacado  of  Texas, 
the  lava  deserts  of  southern  Idaho,  the  littoral  plain  of  southern 
New  Jersey,  the  lacustrine  plain  of  the  Red  River  of  the  North. 
The  areas  included  in  these  views  show  no  signs  whatever  of  de- 
structive processes ;  the  surfaces  are  essentially  as  flat  as  when 
they  were  born.  A  pair  of  drumlins  in  Boston  harbor  and  a  glacial 
sand  plain  in  Newtonville,  Massachusetts,  as  represented  in  a 
model  by  Mr.  Gulliver,  introduce  examples  of  peculiar  forms, 
which  really  belong  among  the  "  forms  taken  by  the  waste  of 
the  land  on  its  way  to  the  sea,"  under  certain  special  conditions, 
and  they  will  be  reviewed  in  a  later  chapter  of  the  course  under 
that  heading.  The  drumlins  and  the  sand  plain  may  also  be 
regarded  merely  as  evidence  of  a  glacial  accident  during  the 
denudation  of  the  New  England  plateau. 

Passing  next  to  illustrations  of  young  sequential  forms,  Mt. 
Shasta  is  exhibited,  with  great  valleys  worn  down  its  flanks.  It 
is  at  once  pointed  out  that  these  gullies  follow  lines  of  construc- 
tional slope,  that  they  began  as  the  paths  of  initial  streams,  de- 
fined by  some  accidental  irregularity  in  the  form  of  the  volcanic 
cone,  and  that  they  are  now  slightly  advanced  in  their  conse- 
quent growth.  The  Mancos  canon  in  Colorado  illustrates  the 
beginning  of  the  dissection  of  a  plateau,  the  consequent  stream 
having  here  cut  down  a  steep-sided  consequent  valley,  but  ap- 
parently not  having  yet  graded  its  slope.  A  stream  in  Florida, 
hardly  incised  in  the  low  coastal  plain,  illustrates  the  faint  relief 
permitted  in  surfaces  that  stand  but  little  above  their  base-level. 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  185 

The  Colorado,  in  its  cafton,  is  another  example  of  an  early  stage 
of  development,  but  it  possesses  an  extreme  intensity  of  relief 
because  of  the  great  altitude  of  its  plateau  :  not  an  old  valley, 
but  a  precocious  young  valley ;  not  a  vast  work,  except  in  our 
inappropriate  human  measures,  but  the  good  beginning  of  a  vast 
work.  The  Elbe  above  Dresden  offers  illustration  of  a  later  stage 
than  the  three  preceding ;  it  has  the  beginnings  of  a  flood  plain, 
now  on  one  side,  now  on  the  other  side  of  the  river ;  from  which  it 
is  inferred  that  the  deepening  of  the  valley  has  practically  ceased, 
that  the  river  is  graded,  and  that  the  slower  process  of  valley 
widening  is  now  the  determining  cause  of  topographical  change. 

Views  in  the  Jura  mountains  would  serve  as  examples  of 
adolescent  forms,  combining  an  interesting  measure  of  conse- 
quent and  subsequent  features,  but  I  have  not  yet  succeeded 
in  finding  any  satisfactory  photographs  of  this  region.  Features 
of  maturity,  more  or  less  advanced,  are  found  in  the  retreating 
escarpments  of  the  middle  Ohio  valley  or  of  the  central  denuded 
region  of  Texas,  and  again  in  the  minutely  carved  ranges  of  the 
central  Alps.  For  yet  older  stages  it  is  difficult  to  find  examples 
still  in  the  cycle  in  which  their  old  age  was  reached  ;  but  the 
plain  of  the  middle  Wisconsin  river  and  the  plateau  of  the  mid- 
dle Rhine  are  ideally  satisfactory  illustrations  of  base-leveled  sur- 
faces,— one  being  an  old  plateau,  and  the  other  an  old  mountain 
region,  —  although  both  have  lately  been  brought  into  a  new 
cycle  by  elevation,  allowing  their  rivers  to  cut  narrow  trenches 
beneath  their  even  surfaces.  By  selecting  views  in  which  only 
the  plain  surface  is  seen,  these  examples  make  appropriate  clos- 
ing members  of  the  series  here  described.  At  a  later  time,  when 
the  complications  of  the  cycle  are  in  discussion,  other  views  show- 
ing the  dells  of  Wisconsin  and  the  gorge  of  the  Rhine  may  be 
presented,  thus  giving  a  new  meaning  to  old  examples. 

Systematic  Examination  of  Facts.  While  the  deductive  geo- 
graphical scheme  is  thus  gradually  extended,  while  its  various 
elements  are  illustrated  more  or  less  completely  by  blackboard 
diagrams,  diagrammatic  models,  and  lantern  slides,  an  acquaint- 
ance with  the  facts  of  the  subjects  is  gained  at  the  same  time 
chiefly  through  the  laboratory  work  of  the  course.  This  is  for 
the  most  part  devoted  to  the  examination  of  maps  and  many 


1 86  EDUCATIONAL  ESSAYS 

other  illustrations  of  actual  geographical  forms,  introduced  sys- 
tematically to  represent  the  kinds  of  construction  and  the  stages 
of  development  that  may  be  compared  with  similar  kinds  and 
stages  in  the  deductive  scheme.  I  regard  it  as  essential  that  the 
two  sides  of  the  work  should  advance  together.  The  theoretical 
considerations  of  the  deductive  scheme  and  the  inductive  ob- 
servation, description,  and  generalization  of  the  facts  of  nature 
continually  react  on  each  other  to  mutual  advantage.  They  call 
different  mental  faculties  into  exercise.  Neither  one  can  be  de- 
veloped alone  to  the  best  advantage.  It  is  true  that  the  con- 
sideration of  the  two  sides  of  the  work  at  the  same  time  leads 
to  mental  confusion  on  the  part  of  untrained  or  careless  stu- 
dents, but  this  does  not  seem  to  be  unfortunate.  It  is,  to  be 
sure,  rather  disappointing  for  a  young  fellow  to  find  in  the  mid- 
dle of  the  course  that  his  neglect  of  its  beginning  has  left  him 
hopelessly  behind  his  better-prepared  or  more  persevering  com- 
rades ;  but  it  is  much  more  disappointing  to  see  how  often  col- 
legiate instruction  is  degraded  by  allowing  it  to  fall  to  the  reach 
of  students  who  do  not  know  how,  or  who  do  not  care  to  know 
how,  to  follow  its  proper  quality.  In  work  of  the  kind  that  I  am 
describing,  mental  confusion  soon  overtakes  those  who  are  poorly 
trained  for  mental  effort.  I  do  not  find  that  it  makes  much  dif- 
ference what  subjects  a  student  has  been  trained  in,  provided  that 
he  has  been  well  trained. 

Laboratory  work  is  an  important  element  in  the  study,  because 
there  is  otherwise  no  opportunity  for  deliberate  and  close  obser- 
vation of  geographical  facts.  Even  if  shown  in  the  lectures,  they 
cannot  be  clearly  seen,  and  there  is  no  time  then  for  close  study. 
No  text-book  or  atlas  contains  illustrations  in  sufficient  variety 
for  collegiate  work.  But  in  the  laboratory,  numerous  maps,  views, 
or  models  may  be  exposed  on  walls,  racks,  or  tables,  remaining 
for  a  week  together  and  thus  giving  abundant  time  for  deliberate 
examination.  From  week  to  week  a  change  may  be  made  in  the 
materials;  the  group  for  each  week  corresponding  to  the  group 
of  problems  then  in  hand.  Many  of  the  illustrations  shown  in 
the  first  week  are  repeatedly  brought  forth  again  later  in  the 
course,  always  gaining  new  meaning  as  sharper  outsight  and 
insight  are  directed  to  them.  Many  facts  of  interest  concerning 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  187 

population  and  occupations  may  be  brought  forward  in  this 
connection,  but  it  is  important  that  the  geographical  facts  should 
first  be  clearly  apprehended. 

In  the  reports  that  are  made  on  this  laboratory  work  the 
students  first  describe  the  facts  that  they  have  observed  in 
terms  that  have  no  suggestion  of  explanation.  They  should 
not  say  that  a  certain  region  is  a  base-leveled  surface,  but  that 
it  is  a  lowland  of  faint  relief.  They  should  not  at  first  speak  of 
old  rivers  revived  into  a  second  youth,  but  they  may  say  that 
the  rivers  of  a  certain  region  run  in  deep,  narrow  valleys  below 
an  upland  of  generally  uniform  altitude,  above  which  occasional 
isolated  hills  rise  to  greater  elevations.  This  I  regard  as  ex- 
tremely important,  in  order  to  insure  a  careful  observation  of 
the  facts  in  discussion ;  for  until  the  facts  are  clearly  per- 
ceived, they  cannot  be  precisely  explained.  It  is  unsafe  at  first 
even  to  speak  of  the  flat  region  at  the  mouth  of  a  river  as  a 
delta.  This  term  not  only  denotes  the  form  of  the  surface,  but 
connotes  an  explanation ;  and  in  the  earlier  weeks  of  the  study 
it  is  by  no  means  sure  that  the  observer  fully  perceives  all  the 
facts  of  form  that  are  denoted  by  the  term,  or  that  he  fully 
appreciates  all  the  features  of  the  process  that  are  connoted  in 
its  explanation.  The  outbranching  of  the  distributaries  near  the 
river  mouth,  as  contrasted  with  the  inbranching  of  the  tributaries 
farther  upstream  and  the  faintly  convex  form  of  the  delta  sur- 
face, may  not  be  clearly  observed  unless  they  are  concisely 
formulated  in  a  description.  The  essentially  balanced  relations 
of  carrying  power  and  load  involved  in  the  explanation  of  the 
growth  of  deltas  may  not  be  perceived  unless  it  is  carefully  dis- 
cussed in  making  out  the  scheme  of  river  development.  There 
can  be  no  thoroughness  of  work  where  observation  and  expla- 
nation are  slurred  over  or  confused.  After  observation  and  de- 
scription are  well  advanced,  explanatory  terms  may  be  introduced, 
it  then  being  seen  that  such  terms  imply  a  pairing  off  of  observed 
facts  with  the  appropriate  members  of  the  deductive  scheme. 
This  mental  process  must  become  perfectly  conscious ;  its  sev- 
eral steps  must  be  recognized  in  their  proper  relations.'  No  strong 
grasp  of  the  subject  can  be  gained  until  the  student  sees  clearly 
where  every  part  of  the  work  stands  in  relation  to  the  whole. 


1 88  EDUCATIONAL  ESSAYS 

Topographical  Maps  published  by  the  United  States  Govern- 
ment Bureaus.  It  is  difficult  to  secure  a  full  series  of  facts  for 
laboratory  study.  My  plan  at  present  is  to  select  maps  from  our 
own  surveys  and  from  the  surveys  of  foreign  countries,  with 
little  regard  to  locality  but  with  much  regard  to  geographical 
features.  The  charts  of  our  coast  survey  offer  admirable  illus- 
trations of  littoral  forms  :  for  example,  the  sand-bar  cusps  of 
capes  Hatteras,  Fear,  and  Lookout,  and  their  offshore  shoals, 
all  formed  between  back-set  eddy  currents,  rotating  betwixt  the 
Gulf  Stream  and  coast ;  or  the  blunted  Canaveral  cusp  on  the 
Florida  coast,  and  its  southward  migration  from  a  former  posi- 
tion ;  or  the  fiords  and  islands  of  Maine ;  the  sounds  of  North 
Carolina  ;  the  delta  of  the  Mississippi,  a  geographical  gem.  The 
maps  of  the  Mississippi  River  Commission  offer  remarkable  illus- 
trations of  the  behavior  of  a  large  river  on  its  alluvial  plain.  Its 
meanders,  its  cut-offs,  and  its  oxbow  lakes  are  shown  to  perfec- 
tion. The  eight-sheet  map  of  the  alluvial  basin  of  the  Mississippi, 
prepared  by  this  commission,  can  be  had  for  a  merely  nominal 
charge ;  it  exhibits  the  lower  part  of  the  great  river  in  an 
admirable  manner.  It  tells  the  curious  story  of  streams  that 
descend  from  the  eastern  bluffs,  but  are  unable  to  ascend  across 
the  flood  plain  to  the  Mississippi ;  they  therefore  unite  and  form 
the  Yazoo  river,  which  runs  southward  along  the  eastern  margin 
of  the  flood  plain,  near  the  foot  of  the  bluffs.  It  would  have  to 
pursue  an  independent  course  all  the  way  to  the  Gulf,  were  it 
not  that  the  Mississippi  comes  swinging  across  the  plain  and 
picks  up  the  Yazoo  at  Vicksburg. 

But  it  is  the  topographical  sheets  of  the  United  States  Geo- 
logical Survey  that  afford  the  greatest  variety  of  illustrative 
material  for  this  country ;  and  it  is  not  too  much  to  say  that 
the  facts  they  present  create  a  revolution  in  the  student's  knowl- 
edge of  his  home  geography.  We  may  well  wish  that  they  were 
more  accurate,  but,  with  all  their  imperfections,  they  present  a 
great  body  of  new  information.  Under  the  family  of  plains  there 
are  examples  of  low  littoral  plains  in  New  Jersey  and  Florida, 
those  of  the  latter  state  being  so  young  that  the  initial  lakes  are 
not  yet  drained.  The  moderate  advance  in  denudation  of  an 
upland  —  itself  an  old  lowland  of  denudation  —  is  seen  in  the 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  189 

meandering  gorge  of  the  Osage  in  central  Missouri;  the  relatively 
uncut  plateaus  of  Arizona  are  seen  alongside  of  the  beginning  of 
their  denudation  in  the  Grand  canon  of  the  Colorado.  Maturely 
dissected  plateaus  are  found  in  West  Virginia  and  eastern  Ken- 
tucky, and  in  northern  Alabama  and  northern  Arkansas;  but  the 
first  two  are  of  minute  topographical  texture  ;  the  second  two  are 
of  coarser  forms.  Outliers  of  past-mature  plateaus  are  shown  on 
several  sheets  in  central  Texas.  All  manner  of  other  illustrations 
are  found  in  the  same  series  of  maps:  the  thoroughly  adjusted 
streams  of  the  Pennsylvania  Appalachians  ;  the  superimposed 
streams  of  northern  New  Jersey ;  the  Illinois  river,  the  type  of 
a  medium-sized  river  in  the  abandoned  channel  of  a  large  river  — 
this  being  the  only  well-mapped  example  of  the  kind  in  this  coun- 
try;  the  warped  intermontane  valleys  of  Montana ;  Crater  lake  in 
northern  California  ;  glacial  lakes  in  Massachusetts  ;  flood  plains 
slanting  away  from  their  river  in  Louisiana ;  fiords  in  Connecticut ; 
moraines  in  Rhode  Island ;  drumlins  in  Wisconsin ;  trap  ridges 
in  New  Jersey ;  revived  old  mountains  in  North  Carolina  ;  half- 
buried  mountains  in  Utah  and  Nevada.  Every  new  package  of 
these  maps  brings  some  new  illustration,  which  is  put  in  use  as 
soon  as  opportunity  allows.  One  of  the  latest  is  a  peculiar  case 
in  southern  California :  a  number  of  small  rivers  are  here  seen 
running  down  from  the  Coast  range  to  the  shore  of  the  Pacific ; 
but  their  mouths  are  all  shut  up  by  sand  bars  in  the  most  sum- 
mary manner ! 

These  maps  are  simply  indispensable.  They  call  forth  much 
interest  from  the  class.  At  first  hardly  translatable  into  words, 
their  meaning  grows  plainer  and  plainer,  until  at  the  close  of  the 
course  they  are  as  suggestive  as  they  were  uncommunicative  at 
the  beginning. 

Foreign  Topographical  Maps.  Not  less  valuable  and  far  more 
accurate  than  our  own  topographical  sheets  are  those  of  various 
foreign  topographical  surveys.  Unfortunately,  the  relief  in  most 
of  these  is  expressed  by  hachures,  altitudes  being  given  only  for 
occasional  points,  or  by  widely  separated  contour  lines ;  but  the 
general  expression  of  the  surface  is  certainly  admirably  rendered 
in  many  of  the  surveys.  The  older  maps  are  generally  too  heavily 
burdened  with  hachures,  but  the  more  modern  surveys  are  very 


190  EDUCATIONAL  ESSAYS 

artistically  executed.  It  has  been  my  practice  for  several  years 
past  to  select  certain  groups  of  sheets  from  the  sets  of  foreign 
topographical  maps  in  our  college  library  and  order  extra  copies 
of  these  groups,  mount  them  on  cloth  and  rollers,  and  thus  pre- 
pare them  for  the  most  convenient  use  in  the  laboratory.  Both 
the  library  and  laboratory  collections  of  this  kind  are  increasing 
year  by  year,  and  I  shall  soon  prepare  a  special  account  of  the 
grouped  sheets,  in  the  hope  that  others  may  perceive  their  great 
value  and  introduce  them  as  teaching  materials  as  far  as  possible. 
Without  specifying  all  that  have  been  thus  far  secured,  I  may 
briefly  mention  some  of  the  more  interesting  examples. 

From  the  Army  Staff  map  of  France  (i  :  80,000)  there  is  a 
group  of  sheets  showing  the  level  plain  of  the  Landes,  with  its 
exceptionally  straight  shore-line  and  its  wide  belt  of  littoral  sand 
dunes  ;  the  beautiful  group  of  radial  rivers  flowing  down  the 
slopes  of  a  great  alluvial  fan  that  has  been  formed  where  several 
large  rivers  emerge  from  the  Pyrenees  —  this  being  one  of  the 
best  examples  of  a  simple,  consequent  river-grouping  that  I  have 
found ;  the  plateau  of  the  lower  Seine,  an  old  upland  of  denuda- 
tion, with  an  excellent  meandering  river  gorge  of  moderate  depth 
cut  through  it,  together  with  certain  interesting  features  of  young 
branching  river  valleys,  and  of  rivers  that  have  been  shortened 
by  the  encroachments  of  the  sea  in  cutting  away  the  land.  To 
these  I  intend  shortly  to  add  groups  of  sheets  snowing  the  dis- 
sected escarpment  west  of  Rheims  and  Chalons,  with  its  beauti- 
fully adjusted  rivers,  the  delta  of  the  Rhone,  and  the  fiorded 
coast  of  Brittany. 

From  the  Ordnance  Survey  of  Great  Britain  (i  163,360)  one 
set  of  sheets  includes  the  central  Highlands  of  Scotland,  with  the 
Great  Glen  and  Glenroy ;  two  other  sets  include  the  fiords  and 
islands  of  the  southwestern  and  the  northwestern  coasts.  These 
three  sets  agree  in  showing  an  old  peneplain  of  denudation,  once 
elevated  and  maturely  dissected,  but  now  somewhat  depressed, 
with  cliffs  nipped  on  its  land  heads  and  deltas  laid  in  its  bay 
heads.  Their  formula,  according  to  the  plan  already  suggested, 
would  be  75,  +  25,  —  2.  A  glacial  accident  of  late  date  is  re- 
corded by  the  upland  tarns  and  the  valley  lakes.  A  group  of 
sheets  for  southwestern  Ireland  exhibits  bold  mountain  ranges 


GEOGRAPHY  AS  A  UNIVERSITY  STUDY  191 

running  directly  into  the  sea,  forming  a  strongly  serrated  coast. 
The  English  sheets  are  of  older  date  and  are  not  of  particularly 
good  expression,  and  for  this  reason  I  have  not  yet  ordered  any 
of  them,  although  the  ragged  escarpment  of  the  chalk  and  of  the 
oolite  trending  northeast  on  either  side  of  Oxford  should  be 
represented,  and  the  Weald  offers  excellent  illustration  of  well- 
adjusted  consequent  and  subsequent  rivers  on  an  unroofed  dome 
of  Cretaceous  strata. 

The  map  of  the  German  Empire  (i  :  100,000)  supplies  many 
examples  of  striking  features.  The  plateau  of  the  middle  Rhine 
has  already  been  mentioned  as  a  subject  for  lantern  slides  ;  it  is 
represented  in  two  map  groups,  one  of  which  shows  the  trans- 
verse gorge  of  the  Rhine  ;  the  other  includes  the  meandering 
gorge  of  the  Moselle,  with  a  perfect  showing  of  its  abandoned 
cut-offs  among  the  hills.  The  flood  plain  of  the  Rhine  about 
Mannheim  exhibits  the  former  meanders  and  the  present  con- 
trolled course  of  the  river,  foreshadowing  the  future  control  of 
the  Mississippi ;  the  morainic  country  of  Prussia  is  a  medley  of 
hills  and  hollows ;  the  Vistula  turns  sharply  at  its  Bromberg 
elbow  from  the  valley  that  it  once  followed,  but  which  it  now 
abandons  to  the  little  Netze  ;  long,  curving  sand  bars  form  the 
two  inclosed  bays  of  eastern  Prussia  (the  Frische  and  Kurische 
Haffe).  From  Norway  (i  :  100,000)  the  district  of  the  Christiania 
fiord  is  already  received  in  ten  sheets  of  most  delicate  execution, 
—  the  greater  fiords  of  the  western  coast  will  be  ordered  as  soon 
as  fully  published  ;  from  Russia  (i  1400,000),  the  lakes  of  Fin- 
land and  of  the  lower  Danube ;  from  Austria,  a  portion  of  the 
flood  plain  of  the  Danube  and  a  strip  of  the  fiorded  coast  of  the 
northern  Adriatic.  This  is  only  a  beginning  of  what  I  hope 
the  collection  may  be  in  a  few  years. 

I  cannot  speak  too  highly  of  the  educative  quality  of  these 
grouped  sheets.  It  is,  in  the  first  place,  a  good  thing  for  students 
to  inspect,  as  closely  as  they  may  in  laboratory  work  of  this 
kind,  the  very  best  products  of  geographical  art.  Their  ideals 
are  thus  raised  above  the  commonplace  level.  Whatever  they 
afterwards  see  will  be  compared  with  a  high  standard.  A  feeling 
of  dissatisfaction  will  arise  regarding  the  very  inferior  maps  of 
their  home  states,  to  which  they  have  been  inured,  and  from  this 


192  EDUCATIONAL  ESSAYS 

a  demand  will  grow  for  the  continuation  and  improvement  of  the 
mapping  of  our  country  that  is  now  going  on.  In  the  second 
place,  the  facts  of  the  subject  are  placed  before  the  student  so 
closely  that  he  cannot  fail  to  be  impressed  at  once  with  their 
real  features  ;  and  these  he  will  find  so  numerous  and  so  varied 
that  he  will  perceive  the  need  of  serious  study  for  their  appre- 
hension. No  verbal  descriptions  from  the  teacher  suffice  to  re- 
place the  portrayal  of  geographical  relief  on  good  maps. 

Classification  of  Initial  Forms.  It  is  only  after  the  deductive 
scheme  is  well  advanced,  and  after  many  examples  of  facts  have 
been  correlated  with  it,  that  I  introduce  a  classification  of  initial 
forms.  Some  such  classification  is  essential,  but  it  is  difficult  to 
establish  satisfactorily,  because  of  the  endless  variety  of  struc- 
tures found  in  nature.  At  present  in  the  elementary  course  I 
recognize  only  plains  and  plateaus  of  horizontal  strata  ;  mountains 
of  disordered  strata,  with  many  minor  subdivisions ;  and  in  a 
subordinate  way,  volcanic  cones  and  flows,  and  glacial  hills  and 
moraines.  Like  the  more  difficult  orders  of  plants  in  an  elemen- 
tary course  on  botany,  mountains  must  be  treated  briefly  in  an 
elementary  course  on  physical  geography,  and  their  fuller  treat- 
ment left  for  more  advanced  study.  After  the  various  kinds  of 
initial  forms  are  treated,  it  is  advisable  to  review  the  features  of 
rivers,  with  their  divides,  lakes,  waterfalls,  flood  plains,  and  deltas  ; 
and  in  this  connection  a  week  or  two  may  be  given  to  the  forms 
assumed  by  the  waste  of  the  land  on  the  way  to  the  sea.  The 
distribution  of  different  kinds  of  forms  should  be  briefly  given 
with  their  classification. 

When  thus  developed,  physical  geography  may  worthily  claim 
the  dignity  of  a  university  study.  Its  subject-matter  is  of  impor- 
tance in  itself,  as  well  as  in  its  relations  to  geology,  zoology,  and 
botany,  or  to  history  and  economics.  Its  methods  are  of  value 
in  training  various  mental  faculties  :  observation,  description, 
generalization,  imagination,  comparison,  discrimination,  these  are 
all  cultivated  to  a  high  degree  in  the  student  who  successfully 
utilizes  the  opportunities  of  the  course. 


X 

METHODS  AND  MODELS  IN  GEOGRAPHICAL 
TEACHING1 

In  presenting  to  the  Association  certain  considerations  regard- 
ing methods  of  teaching  geography,  I  venture  to  assume  that 
your  interests- in  educational  matters  extend  so  far  down  as  to 
reach  a  subject  which  many  scholars  "finish"  early  in  their 
course,  and  whose  advanced  study  hardly  receives  its  due  place 
in  our  colleges  ;  certainly  it  has  suffered  from  neglect.  My  own 
practice  in  the  way  of  teaching  it  has  been  with  college  students 
in  the  division  of  physical  geography,  and  not  feeling  entirely 
satisfied  with  the  system  of  study  as  presented  in  the  text-books 
in  current  use,  I  have  endeavored  to  discover  and  supply  certain 
elements  by  which  instruction  in  the  subject  might  be  advanced. 

The  first  element  that  should  be  supplied  is  one  by  which  the 
conceptions  which  the  teacher  has  in  mind  can  be  vividly  trans- 
ferred to  the  student.  The  teacher  bases  his  mental  pictures  on 
something  he  has  seen,  if  he  is  so  fortunate  as  to  have  traveled 
and  brought  home  with  him  fresh  memories  of  the  morphology 
of  the  earth's  surface ;  or  if  not  an  observer  himself,  he  has  at 
least  had  time  to  gain  his  geographical  conceptions  slowly,  and 
with  the  aid  of  various  descriptions  and  illustrations  that  he  can- 
not present  in  their  entirety  to  his  class.  How  shall  his  ideas  be 
passed  on  to  his  students  ?  Maps  and  pictures  are  of  value,  but 
as  a  rule  they  are  of  low  quality,  except  for  the  larger  parts  of 
the  world.  They  present  no  sufficient  expression  of  the  forms  of 
moderate  size  on  which  we  live.  Photographs  are  excellent  as 
illustrations  of  actual  landscapes,  yet  they  are  too  often  chosen 
with  other  than  geographical  reasons  for  the  choice,  and  but  few 
schools  have  them  in  sufficient  variety.  Moreover,  all  these  aids 
lack  one  element  of  great  value,  namely,  the  third  dimension  that 

1  A  lecture  delivered  before  the  Scientific  Association  of  Johns  Hopkins  Uni- 
versity, February  13,  1889. 

193 


194  EDUCATIONAL  ESSAYS 

so  strongly  characterizes  all  geographical  forms.  I  have  therefore 
desired  to  use  geographical  models,  which  very  easily  give  clear 
indication  of  the  relief  of  a  surface,  and  if  without  all  its  detail, 
still  possess  effective  and  suggestive  form.  Models  are  therefore 
to  be  taken  as  one  of  the  means  of  improving  the  methods  of 
illustrating  what  the  teacher  wishes  to  place  before  the  class. 

Again,  physical  geography  as  ordinarily  defined  is  too  largely 
merely  descriptive,  and  not  physical  at  all.  Indeed,  geography, 
which  is  supposed  to  treat  of  the  form  of  the  surface  of  the  earth, 
neglects  the  form  of  the  earth's  surface  to  an  unfortunate  extent. 
We  hear  much  about  the  connection  between  geography  and  his- 
tory, for  example  ;  but  what  is  this  subject  that  is  connected  with 
history  ?  Where  is  geography  itself  taught  with  the  same  thor- 
oughness that  characterizes  the  modern  teaching  of  the  biological 
sciences  ?  We  recognize,  of  course,  the  vital  connection  between 
geography  and  history,  just  as  the  botanist  recognizes  the  con- 
nection between  botany  and  medicine  ;  but  what  botanist  would 
be  satisfied  to  conclude  the  teaching  of  his  science,  or  even  its 
elements,  at  the  point  that  would  suffice  for  the  collector  of  med- 
ical herbs  or  for  the  doctor  of  medicine  ?  And  why  should  the 
geographer  be  satisfied  with  so  brief  an  outline  of  his  science  as 
will  suffice  for  illustrating  its  connection  with  history  ?  The  sub- 
ject deserves  study  for  its  own  worthy  self  ;  it  is  in  this  line  that 
the  teacher  of  geography  must  wish  to  see  it  developed,  and  it  is 
to  this  end  that  he  must  strive,  just  as  his  colleagues  strive  to 
advance  the  study  of  their  respective  sciences  for  their  own  sake, 
and  not  merely  for  the  illustration  of  some  other.  For  this  reason 
I  have  endeavored  to  examine  the  forms  of  the  land  surface  in 
detail,  and  to  arrange  them  in  their  genetic  relations,  in  order  to 
come  to  a  closer  appreciation  of  the  meaning  of  the  form  of  the 
earth  and  its  development.  In  this  way,  it  seems  to  me,  we  may 
best  study  the  fundamental  material  of  geography.  A  year  ago 
I  had  the  pleasure  of  presenting  some  outlines  of  a  geographical 
classification  at  a  meeting  of  the  National  Geographical  Society 
in  Washington,  and  now  I  would  add  thereto  some  account  of 
certain  geographical  models,  designed  for  the  Teachers  School  of 
Science  under  the  Boston  Society  of  Natural  History,  as  a  means 
of  illustrating  this  classification.  Some  of  the  models  illustrate 


MODELS  IN  GEOGRAPHICAL  TEACHING  195 

the  development  of  plains  and  plateaus ;  some  present  the  vari- 
ous forms  of  volcanic  cones  and  lava  flows ;  others  indicate  the 
changes  in  the  features  of  a  river  as  it  grows  old,  or  as  it  is 
embarrassed  by  glacial  or  volcanic  accidents.  It  is  essential  that 
we  should  study  the  surface  of  the  land  by  means  of  types,  for 
it  would  be  as  impossible  for  a  scholar  to  learn  all  the  individual 
forms  of  the  land  as  it  would  for  the  young  botanist  to  learn  all 
the  individual  plants  of  the  world,  especially  if  they  were  brought 
before  him  in  the  order  of  their  occurrence  over  the  world,  and 
not  in  accordance  with  some  well-tried  system  of  logical  and  nat- 
ural classification.  Botanists  and  zoologists  believe  that  it  is  time 
enough  for  their  scholars  to  study  the  complex  congeries  of  forms 
that  constitute  the  fauna  or  flora  of  a  country  when  they  have  mas- 
tered the  rudiments  of  the  subject  by  careful  study  of  a  moderate 
number  of  typical  examples  of  plants  or  animals;  and,  indeed, 
in  the  modern  development  of  the  study  of  biology,  one  may  see 
the  strongest  contrast  with  the  older  methods  in  this  respect. 
I  should  be  glad  to  see  a  similar  change  overtake  the  conserva- 
tive science  to  which  my  studies  are  devoted. 

In  order  to  give  specific  illustration  of  the  method  of  study  by 
geographical  types  and  the  use  of  models,  let  me  ask  your  con- 
sideration of  that  large  group  of  land  forms  that  may  be  included 
in  the  category  of  plains,  plateaus,  and  their  derivatives.  There 
is  a  brief  preliminary  consideration. 

Any  mass  of  land  constituting  a  single  geographical  individual, 
or  a  natural  group  of  such  individuals,  must,  as  soon  as  it  is  ex- 
posed to  the  destructive  forces  of  the  atmosphere,  begin  its  long 
sequence  of  development ;  and  if  no  change  of  level  happen  to  it, 
it  must  at  length  be  worn  down  smooth  and  low  to  a  featureless 
plain.  When  this  work  begins,  with  every  mark  of  immaturity 
in  its  small  accomplishment,  we  may  regard  the  individual  as 
young,  that  is,  but  little  advanced  in  the  long  cycle  of  systematic 
change  through  which  it  is  destined  to  pass.  When  much  more 
work  has  been  accomplished,  and  the  variety  of  form  resulting  is 
at  its  greatest,  the  individual  may  be  called  mature ;  and  finally, 
when  the  features  of  maturity  weaken  as  the  relief  is  reduced 
and  intensity  of  form  is  lost,  we  find  a  resemblance  to  organic 
decay,  and  are  warranted  in  the  use  of  such  a  term  as  old  age. 


196  EDUCATIONAL  ESSAYS 

But  you  may  say  that  all  this  is  geology,  not  geography.  Geo- 
logical processes  are  indeed  at  work  in  carrying  the  geographical 
individual  through  its  successive  forms,  but  we  are  not  concerned 
with  the  processes,  only  with  the  result.  In  organic  growth,  the 
process  is  chemical ;  but,  for  all  that,  biology  is  not  chemistry. 
Moreover,  if  the  several  forms  assumed  by  a  geographical  indi- 
vidual are  geological  affairs,  we  might  expect  to  find  them  treated 
in  the  standard  works  on  that  science ;  but,  except  in  brief  out- 
line, nowhere  do  they  appear  in  such  books.  Geology  is  too  much 
occupied  with  matters  of  underground  structure,  with  questions 
of  constructive  and  destructive  processes,  and  with  composition 
and  fossil  contents  of  rocks  to  be  awake  to  another  large  ques- 
tion. The  study  of  the  form  of  the  earth's  surface,  even  though 
recognizing  that  the  form  changes,  is  geography.  But,  after  all, 
geography  and  geology  are  one  science,  treating  of  the  earth, 
and  it  is  needless  for  us  to  embarrass  our  work  by  attempting 
unnecessary  subdivision  and  limitation  of  the  fields  that  the  two 
branches  shall  occupy.  Let  each  one  take  whatever  will  aid  its 
attainment  of  the  desired  end.  If  we  can  understand  geographical 
morphology  better  by  some  consideration  of  geological  structure, 
let  it  be  introduced,  just  as  chemistry  is  introduced  into  physiol- 
ogy, or  physics  into  meteorology.  Surely  geologists  have  em- 
ployed geographical  methods  freely  enough  to  warrant  our 
reversing  the  relation.  If  some  consideration  of  geological  proc- 
esses will  serve  our  purpose  and  give  better  appreciation  of  the 
sequence  of  forms  that  geographical  individuals  pass  through, 
then  call  freely  on  geology  for  such  consideration,  and  use  it  to 
the  best  advantage.  Do  not  hamper  our  endeavor  to  understand 
the  form  of  the  earth's  surface  by  any  arbitrary  limitation  of  the 
means  that  we  shall  employ  to  the  end.  It  is  plainly  apparent 
that  geology  and  geography  are  parts  of  one  great  subject,  as 
ancient  and  modern  histories  are,  and  they  must  not  be  consid- 
ered independently.  Indeed,  it  is  only  in  this  close  relation  that 
a  satisfactory  definition  of  the  two  terrestrial  sciences  is  obtained. 
Mackinder  has  concisely  said  that  geology  is  the  study  of  the  past, 
considered  in  the  light  of  the  present,  and  geography  is  the  study 
of  the  present,  considered  in  the  light  of  the  past.  I  can  quote 
no  better  indication  of  the  close  connection  of  the  two  divisions 


MODELS  IN  GEOGRAPHICAL  TEACHING  197 

of  the  world's  history.  Without  going  further  into  abstract  con- 
siderations, we  may  now  turn  to  our  concrete  examples. 

The  so-called  "  valley"  of  the  Red  River  of  the  North  in  Min- 
nesota and  Dakota  is  a  broad  plain  of  exceedingly  level  surface. 
It  is  so  truly  level  that  it  illustrates  the  curvature  of  the  earth 
in  the  same  way  that  it  is  seen  at  sea ;  for  in  crossing  the  plain, 
first  a  distant  tree-top  is  seen  above  the  horizon,  then  a  house- 
top, and  at  last  the  body  of  the  house  rises  into  full  view,  just 
as  the  upper  and  lower  sails  and  the  hull  of  the  ship  are  brought 
into  sight  in  sailing  toward  it  on  the  ocean.  T'his  broad  plain 
is  a  lake  bottom,  whence  the  water  in  which  its  fine  sediments 
were  laid  down  has  been  drained  away,  and  drained  away  by  so 
curious  a  process  that  if,  in  teaching  modern  history,  it  were 
noted  that  some  existing  form  of  government  were  as  curiously 
related  to  the  past,  no  teacher  would  hesitate  to  make  reference 
to  it.  The  northern  barrier  that  held  the  waters  of  the  lake  was 
the  southward  front  slope  of  a  great  sheet  of  ice  that  for  a  time 
obstructed  the  open  northward  drainage ;  and  in  the  lake  thus 
created,  fine  sediments  were  spread  out  so  plentifully  that  they 
buried  the  former  surface  of  the  land,  and  so  evenly  that  when 
the  waters  were  drained  away  as  the  ice  melted,  a  dead-level 
plain  was  revealed. 

The  plain  stands  well  above  sea-level,  and  hence  must  suffer 
change  as  destructive  processes  attack  it.  Why,  then,  is  it 
so  smooth  ?  Manifestly  because  it  is  young.  There  has  not  yet 
been  time. for  streams  to  channel  it.  It  is  extremely  immature, 
truly  infantile  in  its  appearance,  with  scarcely  a  sign  of  the  va- 
riety of  features  that  will  be  developed  in  its  later  history.  Does 
not  this  consideration  lend  additional  interest  to  the  study  of  so 
simple  and  monotonous  a  district  as  a  plain  of  the  Red  River  of 
the  North  ?  Is  there  not  a  keener  appreciation  of  its  peculiari- 
ties gained  by  looking  at  them  in  the  light  of  their  development, 
instead  of  describing  them  simply  as  absolute  forms,  not  other- 
wise considered  ? 

The  Red  river  plain  has,  however,  begun  its  development. 
The  Red  river  itself  has  incised  a  narrow,  steep-sided  trench 
twenty  or  forty  feet  deep  in  the  surface  of  the  plain,  and  the  few 
side  branches  of  the  river  have  narrower  and  shallower  channels. 


1 98  EDUCATIONAL  ESSAYS 

These  trenches  and  channels  are  simply  young  valleys,  and  they 
are  growing  so  rapidly  that  their  increase  in  length  and  width  is 
noticeable  even  in  the  past  few  years  of  settlement.  But  still 
the  streams  have  barely  made  a  beginning  of  the  great  work  of 
carrying  away  all  the  material  of  the  plain  above  base-level,  this 
being  their  manifest  future  task.  So  little  has  been  done  as  yet 
in  the  way  of  preparing  drainage  channels  that  the  rain  which 
falls  here  is  greatly  delayed  in  reaching  a  stream  course  by  which 
it  may  flow  to  its  goal,  the  sea,  and  so  much  of  it  stands  about 
idly,  instead  of  quickly  running  off,  that  it  is  in  good  part  evapo- 
rated and  carried  away  through  the  air.  Evidently  we  have  here 
to  do  with  a  geographical  individual  that  is  just  entering  its  career, 
that  still  retains  its  embryonic  characteristics,  so  little  has  it 
advanced  in  its  life  history. 

Can  we  not  foretell  something  of  the  future  history  of  this 
plain  ?  As  the  rivers  carve  their  trenches  deeper  and  deeper, 
and  the  inclosing  slopes  are  wasted  away  and  widen  out,  and  the 
little  side  gullies  eat  backwards  and  increase  in  length  till  they 
become  ravines  and  the  ravines  grow  into  valleys,  then  the  inter- 
stream  surface,  at  first  smooth  and  unbroken,  is  traversed  in  all 
directions  by  branching  water  courses  ;  the  rainfall  is  much  more 
quickly  led  into  the  streams,  —  everything  marks  a  more  advanced 
stage,  all  of  whose  features  are  indicated  in  one  of  the  models  of  the 
plain  and  plateau  series.  But  we  can  not  only  predict  the  future 
of  the  Red  river  plains :  we  can  find  examples  of  other  plains, 
born  at  an  earlier  time,  that  are  now  in  the  advanced  stage  that 
the  Red  river  plains  have  yet  to  reach.  Look  at  the  coastal  plains 
of  the  Carolinas.  They  are  the  old  bottom  of  the  Atlantic,  laid 
bare  by  a  relative  uplift  of  the  continent.  They  are  well  drained  ; 
many  streams  run  across  them,  and  many  branches  give  ready 
discharge  to  the  rainfall ;  the  channels  are  deeper  below  the  gen- 
eral level  of  the  country  than  are  those  of  the  Red  river  plains, 
and  the  interstream  surface  is  much  more  broken,  yet  still 
enough  of  it  remains  to  make  it  clear  that  the  present  form  is 
developed  from  an  originally  level,  unbroken  plain ;  and  a  close 
comparison  will  leave  no  doubt  that  the  coastal  plains  of  the 
Carolinas  differ  from  the  Red  river  plains  chiefly  in  being  further 
advanced  in  their  cycle  of  development.  They  are  closely  related 


MODELS  IN  GEOGRAPHICAL  TEACHING  199 

individuals,  but  they  differ  somewhat  in  age.  They  are  like  the 
egg  of  a  caterpillar  and  the  caterpillar  itself,  —  not  very  similar  at 
first,  and  not  like  what  they  will  come  to  be  later  on,  but  closely 
comparable  for  all  that ;  their  differences  only  manifest  their 
relationship ;  what  one  is,  the  other  will  be ;  what  the  other  is, 
the  first  has  been.  Thus  we  can  introduce  into  geography  the 
element  of  growth,  that  is,  systematic  change,  and  greatly  to  the 
enlivenment  of  the  study.  It  is  often  the  reproach  of  geography 
that  it  does  not  deal  with  things  having  life,  but  this  is  true  only 
if  we  do  not  take  heed  of  the  kind  of  life  that  it  may  consider. 
One  may  say  that  the  changes  here  discussed  are  so  slow  that 
we  need  not  take  account  of  them,  but  this  is  predetermining 
what  we  shall  and  what  we  shall  not  study ;  let  us  rather  see  if 
the  consideration  of  slow  geographical  life  does  not  impart  new 
meaning  to  an  old  study  ;  let  us  question  if  this  new  meaning  is 
not  nearer  the  truth  that  we  are  striving  for ;  then  we  shall  be 
in  a  better  position  to  judge  if  slowness  of  change  is  a  reason  for 
its  neglect.  No  one  makes  objection  to  teaching  a  young  scholar 
about  the  growth  of  an  oak  tree  from  an  acorn,  though  it  is  safe 
to  say  that  no  scholar  comes  to  the  belief  of  the  growth  of  an 
oak  from  witnessing  it ;  he  is  convinced  of  a  change  that  he  can- 
not wait  to  see,  partly  by  comparison  with  trees  of  a  faster 
growth,  and  partly  by  seeing  oaks  of  different  sizes,  and  being 
led  to  make  reasonable  generalizations  on  his  observations.  It  is 
the  same  with  our  understanding  of  geographical  growth  ;  we  can- 
not see  much  of  it,  —  not  even  the  oldest  of  us,  —  and  yet,  after 
the  conception  is  once  gained,  it  becomes  so  vivid  that  one  can 
hardly  help  expecting  to  find  that  a  change  is  perceptible  on  re- 
turning after  a  time  to  some  familiar  locality.  One  may  see  a 
sand  bank  washed  away  by  a  heavy  rain,  and  from  this  to  the 
washing  down  of  the  largest  mountain  there  is  only  a  difference 
of  degree,  not  of  kind.  A  scholar  may  easily  comprehend  the 
change  of  form  indicated  by  the  differences  between  the  two 
plains  already  described,  and  unless  his  natural  intelligence  is 
obstructed,  he  can  then  grasp  the  idea  of  geographical  growth. 
Let  us  next  look  at  West  Virginia,  typified  in  the  second 
model  of  the  series  ;  here  the  interstream  hills  are  so  high  that 
they  almost  merit  the  name  of  mountains ;  the  stream  branches 


200  EDUCATIONAL  ESSAYS 

have  become  so  numerous  that  no  part  of  the  original  level  up- 
land surface  remains ;  every  part  has  an  immediate  slope  to  a 
stream,  and  the  drainage  system  is  advanced  to  its  highest  de- 
velopment. Indeed,  we  need  some  aid  here  from  geology  to  be 
sure  that  we  are  dealing  with  an  individual  of  the  same  kind  as 
those  already  considered,  so  little  likeness  is  there  between  this 
one  and  the  others.  But  the  aid  from  geology  is  conclusive  ; 
for  West  Virginia  and  a  large  area  around  it  is  made  up  of 
horizontal  layers  of  bedded  rocks  that  once  were  at  the  bottom 
of  the  sea,  and  that  still  retain  the  essentially  horizontal  attitude 
in  which  they  were  laid  down ;  the  whole  mass  of  horizontal 
layers  has  simply  been  raised  with  respect  to  the  surface  of  its 
parent  ocean.  This  elevation  occurred  so  long  ago  that  the  im- 
maturity such  as  still  characterizes  the  Red  river  plains  is  here 
long  past ;  the  adolescence  seen  in  the  Carolina  plains  is  also 
long  ago  lived  through.  In  West  Virginia  we  have  maturity ; 
there  can  be  no  greater  variety  of  form  than  is  here  presented. 
The  relief  of  the  surface  is  at  its  highest  value;  for  while  the 
interstream  hills  have  not  lost  much  of  their  original  height,  the 
valleys  have  been  sunk  about  as  low  as  they  can  be,  and  hence 
there  is  the  greatest  possible  difference  of  altitude  between  hill- 
top and  valley -bottom.  The  streams  have  become  very  numerous, 
and  can  hardly  be  more  so ;  every  part  of  the  surface  is  inter- 
sected by  them.  There  is  no  room  for  more. 

From  this  time  on  the  form  of  the  surface  becomes  less  pro- 
nounced. As  the  destructive  changes  progress  further,  the  val- 
leys can  deepen  but  little,  although  the  hill-tops  must  be  reduced, 
and  the  valley  slopes  must  widen  out,  and  all  the  topographical 
expression  must  weaken  as  old  age  is  approached.  This  is  the 
character  of  central  Kentucky,  and  appears  in  the  third  model 
of  the  set.  Excepting  where  the  valleys  are  inclosed  in  especially 
hard  rocks,  they  are  wide  open,  and  the  variable  height  of  the 
intervening  hills  makes  it  clear  that  they  retain  no  longer  all  of 
the  height  that  they  once  possessed.  They  are  weakening,  pass- 
ing into  forms  of  less  and  less  emphasis,  losing  variety,  becom- 
ing old  and  feeble. 

In  the  next  stage  we  may  expect  to  find  the  valleys  so  far 
widened  that  they  should  form  broad  plains,  smoothly  rolling, 


MODELS  IN  GEOGRAPHICAL  TEACHING  20 1 

essentially  a  lowland  of  faint  relief,  but  occasionally  diversified 
with  hills  of  moderate  height ;  and  thus  the  very  opposite  of  the 
Carolina  plains,  where  the  surface  is  an  upland,  with  occasional 
valleys.  Such  an  old  plain  may  be  seen  about  the  headwaters 
of  the  Missouri,  in  eastern  Montana ;  the  general  surface  is  ex- 
tremely monotonous,  gently  rolling,  and  one  roll  like  the  next, 
so  that  one  may  easily  lose  his  way  in  the  absence  of  landmarks. 
But  here  and  there  over  the  plain  mesas  of  considerable  eleva- 
tion still  remain,  the  reason  for  their  endurance  being  seen  in 
the  layer  of  hard  lava  that  protects  them  and  retards  their  de- 
struction, while  the  rest  of  the  country  has  wasted  away  more 
rapidly.  These  lava  caps  are  old  flows  from  once  active  volca- 
noes ;  the  lava  at  the  time  of  eruption  undoubtedly  ran  down 
from  its  vents  to  the  lowest  ground  that  it  could  find,  and  yet 
it  now  occupies  the  highest  ground,  in  virtue  of  its  obstinate 
refusal  to  waste  away.  Every  such  lava  cap  is  a  witness  to  the 
greater  mass  of  material  over  the  whole  country  when  the  erup- 
tion took  place,  and  the  destruction  of  this  greater  mass  must 
have  progressed  through  the  several  stages  illustrated  by  the 
present  condition  of  the  Red  river  plains,  the  Carolina  plains, 
the  mountains  of  West  Virginia,  and  the  hills  of  central  Ken- 
tucky, before  it  could  have  reached  a  surface  of  faint  relief.  It 
requires  great  faith  in  the  evidence  here  adduced  to  believe  that 
so  stupendous  a  piece  of  work  has  really  been  accomplished.  It 
is  well-nigh  incredible,  and  the  observer  on  the  ground  is  fully 
justified  in  doubting  it  as  long  as  he  can,  but  it  cannot  be 
doubted  when  the  evidence  is  once  well  seized.  It  is  by  no  means 
unparalleled,  and  much  nearer  home  we  may  find  examples  as 
extraordinary,  and  as  far  from  easy  belief,  but  as  necessary  to  the 
convictions  of  the  well-ordered  geographer. 

Such  a  plain  as  that  of  the  upper  Missouri  may  be  called  a 
base-level  plain,  because  it  has  been  worn  down  to  the  con- 
trolling level  of  drainage,  or  to  what  is  called  the  base-level  of 
the  region ;  this  being  in  distinction  to  an  initial  or  new  plain, 
whose  smoothness  is  due  to  the  short  time  that  its  original 
form  has  been  exposed  to  developing  agencies.  A  base-level 
plain  represents  the  ultimate  stage  in  the  sequence  of  a  simple 
cycle  of  development. 


202  EDUCATIONAL  ESSAYS 

Certain  elements  of  importance  yet  remain  to  be  considered. 
If  the  plain  be  raised  to  a  moderate  height  over  sea-level,  it  can 
never  acquire  great  intensity  of  relief,  for  the  streams  are  then 
allowed  but  a  small  depth  to  which  they  can  cut.  If,  on  the  other 
hand,  the  elevation  is  great,  and  rapid  enough  to  be  for  the  most 
part  acquired  before  the  destructive  processes  have  made  great 
headway,  then  the  vertical  element  is  strong,  the  topographical 
relief  is  intense.  Our  coastal  plain  is  an  example  of  a  region  of 
mild  form ;  it  has  but  slight  elevation,  and  hence,  however  long 
the  rivers  flow  across  it,  they  can  never  cut  out  deep  valleys. 
The  plateaus  of  Utah  and  adjacent  parts  of  the  West  are  of  an- 
other sort;  here  the,  elevation  is  excessive,  and  the  depth  of 
cutting  allowed  to  the  rivers  is  correspondingly  great.  Marvel- 
ously  have  they  taken  advantage  of  their  opportunity.  The  val- 
ley cut  by  the  Colorado  and  its  tributaries  is  in  some  places  a 
mile  deep,  and  yet  when  we  see  the  enormous  mass  of  land 
still  lying  on  either  side  of  the  valley  above  base-level  and 
waiting  to  be  carried  down  to  the  ocean,  we  cannot  doubt  that 
the  time  thus  far  employed  in  doing  so  great  a  piece  of  work  is 
a  small  part  of  the  whole  cycle  of  growth.  The  upper  plateau 
surface  is  still  broadly  level,  except  for  certain  irregularities  to 
be  referred  to  later  on ;  the  valley  is  narrow,  even  to  notoriety, 
and  must  therefore  be  called  young.  It  is  a  case  of  precocious 
adolescence.  Intensity  or  faintness  of  relief  are  therefore  varia- 
tions on  the  general  scheme,  and  it  is  my  intention  that  these 
variations  shall  also  be  represented  by  models  when  new  mem- 
bers are  added  to  complete  the  present  series ;  a  young  plateau 
of  intense  relief,  a  middle-aged  plain  of  mild  relief,  will  thus  be- 
come definitely  intelligible  terms  to  our  mind.  Along  with  this, 
it  must  be  perceived  that  two  mature  plains  need  not  be  of  the 
same  age,  if  measured  in  years,  for  the  development  of  maturity 
in  a  high  plateau  requires  more  time  than  in  a  lowland. 

There  is  another  element  of  variation  that  must  be  con- 
sidered. Sometimes  the  simple  cycle  of  development  that  has 
been  described  is  interrupted  :  the  land  does  not  lie  quiet  long 
enough  to  pass  through  a  complete  series  of  changes  without 
disturbance.  Indeed,  this  interruption  is,  except  in  very  young 
plains,  the  rule  and  not  the  exception ;  and  several  of  the 


MODELS  IN  GEOGRAPHICAL  TEACHING  203 

examples  already  given  illustrate  it.  The  coastal  plain  of  the 
Carolinas  has  suffered  a  moderate  depression  since  its  valleys 
were  defined  pretty  much  in  their  present  form,  and  their  lower 
courses  are  thereby  slightly  submerged.  Thus  arise  the  estu- 
aries that  characterize  our  Atlantic  coast,  and  these  are  pre- 
sented in  a  fourth  model.  The  old  base-level  plain  of  the  upper 
Missouri  no  longer  stands  at  the  low  level  in  which  it  was  worn 
down,  but  has  been  elevated  a  thousand  feet  or  more,  and  hence 
all  its  rivers,  that  had  settled  down  to  a  quiet  old  age  of  little 
work,  have  been  rejuvenated,  and  are  now  beginning  a  second 
cycle  of  life.  They  run  swiftly  in  well-defined,  narrow  valleys, 
even  though  the  inclosing  rocks  are  soft ;  and  they  are  some- 
times interrupted  by  waterfalls,  even  when  their  volume  is  as 
large  as  that  of  the  Missouri  above  Fort  Benton.  Manifestly, 
therefore,  the  elevation  of  the  old  plain  is  relatively  recent; 
very  little  advance  has  yet  been  made  in  the  development  of 
its  second  cycle.  The  same  kind  of  complexity  appears  in  the 
high  plateaus  of  Utah  and  Colorado  :  the  high-level  surface  in 
which  the  canons  are  cut  is  not  an  original  surface  of  construc- 
tion, but  is  a  surface  of  considerable  irregularity,  as  has  already 
been  mentioned  ;  part  of  the  irregularity  is  due  to  great  fractures 
which  have  broken  the  country  into  massive  blocks  and  lifted 
them  a  little  unevenly,  and  part  is  due  to  the  incomplete  base- 
leveling  of  the  region  during  a  previous  cycle  of  development, 
when  the  elevation  was  less  than  now.  The  combination  of  old 
and  new  forms  thus  explained  is  the  subject  of  a  fifth  model. 
A  wonderful  addition  is  made  to  our  appreciation  of  a  country 
when  all  these  factors  in  its  history  are  recognized  as  contribut- 
ing essentially  to  its  topography. 

Is  it  not  worth  while  to  try  to  acquire  the  broader  comprehen- 
sion of  geography  that  comes  from  understanding  its  meaning  ? 
Can  we  not  make  immediate  practical  use  of  such  terms  as  infan- 
tile, young,  adolescent,  mature  or  middle-aged,  old,  and  very  old  ? 
Do  they  not  recall  all  the  significance  of  certain  selected  or 
idealized  typical  examples  that  have  been  studied,  being  in  this 
respect  like  the  terms  that  the  botanist  employs  to  so  great  an 
advantage  ?  No  botanist  would  admit  the  superiority  of  para- 
phrases over  terms ;  compactness,  accuracy,  and  intelligibility 


204  EDUCATIONAL  ESSAYS 

would  all  be  sacrificed  if  terms  were  given  up.  And  yet  nearly 
all  geographers  employ  paraphrases  instead  of  terms.  Let  us 
take  an  example  to  illustrate  this  from  the  description  of  certain 
counties  in  Missouri  in  one  of  the  geological  reports  on  that 
state,  to  which,  as  in  other  states,  we  must  generally  go  for  the 
best  geographical  materials. 

The  region  is  one  of  horizontal  structure,  and  therefore  comes 
under  the  general  heading  now  considered.  Of  Miller  county  it 
is  said  :  "  Near  the  Osage  and  its  larger  tributaries  the  country 
is  generally  very  broken  and  rocky,  excepting  immediately  in  the 
valleys  ;  but  farther  back  the  slopes  usually  become  more  gentle, 
with  fewer  exposures  of  rock,  until  we  reach  the  higher  districts, 
more  remote  from  the  streams,  where  the  surface  is  comparatively 
level,  or  but  slightly  undulating."  Again,  of  Morgan  county : 
"  The  surface  of  the  elevated  region  near  the  middle  of  the 
county  is  beautiful,  comparatively  level  or  undulating  prairie  land. 
South  of  this  the  slopes  are  first  gentle,  near  the  head  branches 
of  the  Gravois,  but  as  we  descend  these  the  face  of  the  country 
becomes  more  hilly,  and  almost  everywhere  near  that  and  the 
main  creeks,  as  well  as  their  principal  tributaries,  and  especially 
near  the  Osage,  it  is  very  broken  and  rocky.  North  of  the  main 
divide,  the  high,  nearly  level  prairie  land  extends,  with  a  slight 
descent,  for  some  distance  northward  between  the  streams  flow- 
ing in  that  direction,  but  near  most  of  the  larger  streams  the 
surface  is  more  or  less  broken,  and  sometimes  rocky,  but  gener- 
ally not  so  much  so  as  on  the  south  side." 

What  is  meant  by  this  ?  Manifestly,  the  country  is  an  adoles- 
cent plain  of  moderate  intensity  of  development  and  apparently 
of  simple  history.  The  horizontal  attitude  of  the  rocks  and  the 
level  surface  of  the  uplands  show  us  that  the  region  belongs  to 
the  family  of  plains  or  plateaus  ;  the  irregular  courses  of  the 
streams  and  the  steepness  of  their  banks  decide  with  equal  clear- 
ness that  the  development  of  the  plain  has  not  advanced  very  far. 

Now  in  the  same  report  the  writer  says  that  there  are  oak 
trees  in  the  forests.  Why  does  he  not  say  that  there  are  tall 
vegetable  growths  of  irregular  bifurcations,  bearing  green  ap- 
pendages at  the  attenuated  extremities,  these  appendages  being 
strongly  scalloped  in  outline,  and  so  on  ?  He  also  speaks  of  pines. 


MODELS  IN  GEOGRAPHICAL  TEACHING  205 

Why  not  of  other  vegetable  growths,  with  straight  vertical  axes, 
from  which  lateral  arms  spread  out  with  some  regularity,  bear- 
ing long,  slender  spicules  on  their  minuter  divisions  ?  Instead  of 
this,  he  says  oak  and  pine.  This  is  not  because  all  oaks  and  all 
pines  are  of  precisely  one  pattern.  Their  variations  are  infinite, 
but  for  all  that  they  vary  only  through  a  moderate  range,  and 
can  all  be  brought  under  typical  forms.  They  may  be  young  or 
old,  large  or  small,  well  grown  or  deformed,  living  or  dead,  but 
they  are  still  oaks  or  pines.  How  well  it  is,  therefore,  that  they 
should  be  known  by  a  definite  term  or  name.  How  well  it  would 
be  if  geographical  forms  were  equally  well  named ;  and  why  should 
they  not  be  ?  The  many  plains  that  we  have  described  do  not 
differ  more  greatly  among  themselves  than  the  oaks  or  the 
pines ;  they  deserve  recognition  as  constituting  a  family,  naturally 
related,  not  by  inheritance  from  descent,  as  with  the  trees,  but 
by  similarity  of  the  physical  processes  under  which  they  have 
been  developed.  The  natural  association  of  their  features  de- 
serves just  such  recognition  as  is  implied  by  giving  them  names, 
distinctive  and  well  defined. 

Do  we  not  gain  a  better  understanding  of  the  earth's  surface, 
of  the  primary  object  of  geographical  study,  by  thus  looking  at 
the  meaning  of  land  form,  as  well  as  at  the  form  itself  ?  Is  not 
the  possibility  of  accurate  description  greatly  increased  thereby, 
and  does  not  the  description,  when  made,  carry  more  of  the  de- 
sired meaning  than  ordinary  geographical  narration  in  which 
there  is  no  definite  standard  recognized  for  comparison  ?  The 
reason  of  this  is  not  far  to  seek.  Our  conception  of  the  un- 
known is  based  on  the  conception  of  the  known,  either  by  like- 
ness or  contrast.  Ordinary  geographical  description  has  not 
sufficient  accuracy  because  its  terms  are  vague ;  they  do  not 
bring  up  to  the  mind  the  recollection  of  any  well-defined  type  or 
standard.  Plain,  rolling  country,  hilly  country,  broken  country, 
have  no  precise  meaning ;  they  "  denote  "  but  do  not  "  connote." 
But  when  we  examine  a  series  of  geographical  forms  related  by 
community  of  structure,  though  contrasted  in  age,  and  give  to 
every  one  a  name,  such  as  a  young  plain,  a  mature  or  middle- 
aged  plain,  these  terms  bring  certain  well-marked  conceptions 
before  us,  —  conceptions  that  have  been  elaborated  in  our  study 


206  EDUCATIONAL  ESSAYS 

of  the  type  or  standard  of  reference,  —  and  we  readily  form  a 
mental  picture  in  which  all  the  many  essential  features  of  the 
region  described  are  clearly  appreciated.  An  adolescent  plain, 
for  example,  is  a  surface  of  broad,  even  uplands,  here  and  there 
trenched  across  by  streams  which  follow  valleys  of  moderate 
width ;  the  general  continuity  of  level  from  one  interstream  sur- 
face to  another  comes  to  mind ;  also  the  relative  scarcity  of  the 
smaller  stream  channels  ;  and  the  relation  of  the  region  to  its 
fellows  of  greater  or  less  age. 

It  is  immaterial  what  names  are  used  for  the  present  in  describ- 
ing plains  and  plateaus,  for  none  as  yet  are  authoritatively  ac- 
cepted by  geographers,  but  it  would  be  to  our  common  advantage 
if  experiments  were  made  on  the  use  of  a  larger  set  of  terms  than 
is  commonly  employed.  The  important  point  is  that  terms  based 
on  natural  relationship  should  be  used,  and  that  they  should  be 
familiarized  by  the  study  of  type  forms.  Experiment  will  alone 
decide  what  terms  shall  be  finally  adopted.  My  own  experience 
with  students  of  undergraduate  age  has  shown  me  that  the  idea 
as  here  outlined  is  a  valuable  one,  and  that  the  terms  here  em- 
ployed are  suggestive  and  satisfactory.  I  am  very  desirous  of 
hearing  the  experience  of  others  in  the  same  experimental  line. 

A  few  words  may  be  said  as  to  the  method  of  using  the 
models,  a  method  that  seems  to  me  adapted  to  young  as  well  as 
to  more  advanced  scholars.  A  series  of  models  is  laid  out  on 
the  tables  of  a  room  which,  in  the  schools  of  the  future,  may,  I 
trust,  be  called  the  geographical  laboratory.  Each  student  is 
asked  to  describe  what  he  sees ;  to  note  if  he  can  recognize  any 
features  of  the  miniature  landscape  that  are  already  familiar  to 
him  from  his  own  observation.  He  is  then  told  to  try  to  draw  a 
map  of  the  surface  represented,  or  a  part  of  it  if  the  whole  is 
somewhat  complicated.  More  or  less  aid  must  be  given  here,  as 
so  many  students  are  untrained  in  the  simplest  delineation.  When 
the  map  is  drawn,  show  the  class  a  map  of  some  actual  region  of 
the  same  kind  as  that  typified  in  the  model ;  ask  them  to  notice 
how  far  the  features  that  they  have  drawn  from  the  model  are 
features  on  the  actual  map  ;  let  them  search  for  additional  fea- 
tures, generally  small  ones  that  may  appear  on  the  map,  but  which 
are  not  shown  on  the  model. 


MODELS  IN  GEOGRAPHICAL  TEACHING  207 

Next  produce  the  second  model,  and  go  through  the  same 
process,  but  without  any  suggestion  that  the  first  and  second 
models  are  related.  Finally,  ask  if  any  one  perceives  a  connec- 
tion or  relation  between  the  two  regions  thus  considered.  Few 
can  fail  to  see  it,  and  when  perceived  it  should  be  described  by 
every  member  of  the  class  for  himself.  I  have  great  faith  in 
the  scholar's  own  careful  expression,  both  in  drawing  and  in 
writing,  of  what  he  has  himself  seen  or  thought.  Note  here  that 
the  scholar  need  not  discover  how  the  change  from  one  form  to 
the  next  has  been  produced,  he  need  only  recognize  it  ;  then 
the  teacher  may  supplement  the  recognition  as  far  as  he  wishes 
with  simple  geological  explanation  of  processes.  This  need  not 
go  far,  and  merely  opens  the  way  to  further  study  of  geology. 
The  word  "  geology  "  need  not  be  mentioned. 

If  the  class  be  somewhat  mature,  the  teacher  may,  before 
bringing  out  the  third  model,  ask  for  predictions  of  the  form  of 
future  stages  of  the  region  ;  or,  if  this  seem  venturesome,  the 
simpler  inductive  method  may  still  be  followed.  At  last  the 
models  showing  complications  and  interruptions  in  a  single  cycle 
of  change  may  be  introduced,  all  the  examples  being  illustrated 
by  maps  of  actual  relations,  as  well  as  by  models,  views,  descrip- 
tions, and  in  every  other  way  that  the  ingenuity  of  the  teacher 
devises. 

When  thus  familiarized  with  the  general  conception  of  geo- 
graphical change,  let  the  scholars  attempt  to  make  full  statement 
of  all  they  have  learned  from  the  work  so  far  concerning  geo- 
graphical relationships.  The  brighter  ones  will  here  manifest 
some  perception  of  the  generalizations  that  may  be  based  on  the 
facts  thus  far  presented,  and  from  this  time  on  geographical  form 
has  a  new  and  a  fuller  meaning  to  them.  Additional  examples 
of  the  various  stages  of  development  may  be  introduced  at  the 
discretion  of  the  teacher,  and,  if  time  allow,  they  can  best  be 
taken  from  books  of  travel  and  exploration,  reports  of  state  and 
government  surveys,  and  the  like,  in  order  to  give  some  fresh- 
ness and  reality  to  the  study.  It  is  apparent  enough  that  in  its 
fully  expanded  form  it  will  take  a  long  time  for  the  better  geo- 
graphical teaching  to  enter  the  larger  public  schools,  but  in 
schools  where  teachers  are  numerous  enough  to  give  every 


208  EDUCATIONAL  ESSAYS 

scholar  a  good  share  of  personal  attention,  I  do  not  despair  of 
seeing  geographical  laboratories  and  a  rational  inductive  method 
of  instruction  employed. 

Comparisons  have  already  been  made  between  the  methods 
employed  in  teaching  biology  some  forty  or  fifty  years  ago  and 
during  the  last  decade.  It  seems  to  me  that  physical  geography 
is  still  in  the  undeveloped  condition  that  biology  has  outgrown. 
Our  text-books  of  physical  geography  attempt  to  describe  the 
whole  earth,  just  as  the  old  natural  histories  tried  to  describe 
the  whole  animal  and  vegetable  kingdoms.  Since  the  publica- 
tion of  Huxley  and  Martin's  Biology,  this  plan  has  been  aban- 
doned in  the  better  schools,  and  the  pupil  now  studies  the  few 
typical  forms  that  give  him  a  knowledge  of  the  great  resemblances 
of  animals,  and  does  not  dwell  on  their  minute  differences.  He 
learns  a  good  deal  about  a  few  animals  instead  of  a  very  little 
about  a  great  many.  I  should  like  to  see  the  same  change  in- 
troduced into  the  teaching  of  physical  geography.  It  is  impossi- 
ble for  a  scholar  to  learn  anything  definite  about  the  form  of  the 
earth's  surface  if  he  attempts  to  study  all  the  continents.  He 
might  as  well  attempt,  in  his  botany  lessons,  to  learn  about  the 
distribution  of  forests  instead  of  studying  the  structure  of  plants. 
Something  of  the  grosser  continental  forms  should  of  course  be 
considered,  just  as  it  is  interesting  to  know  something  of  the 
distribution  of  forested  and  of  desert  regions  ;  the  general  dis- 
tribution of  land  and  water,  its  relation  to  climate,  history,  and 
so  on,  —  all  this  is  of  great  interest ;  so  are  the  generalizations 
concerning  evolution  and  the  speculations  concerning  migrations 
in  which  the  biologist  may  indulge,  but  they  do  not  form  the 
chief  matter  of  our  best  elementary  methods,  for  they  cannot 
be  sufficiently  original  with  the  ordinary  student.  When  a  boy 
grows  up  and  travels  over  the  country,  he  never  sees  the  grosser 
continental  forms  ;  they  are  too  large.  He  sees  only  small  forms, 
corresponding  to  the  individual  plants  of  the  forest.  Why  not, 
then,  instruct  him  in  such  a  way  that  he  shall  appreciate  these 
small  forms,  these  geographical  individuals,  just  as  he  is  taught 
to  understand  something  of  botanical  individuals  ?  Let  him  under- 
stand that  there  is  a  geographical  morphology,  perhaps  not  so  pre- 
cise as  that  of  the  organic  world,  but  none  the  less  interesting ; 


MODELS  IN  GEOGRAPHICAL  TEACHING  209 

let  him  feel  that  these  geographical  forms  are  the  results  of 
definite  orderly  processes,  working  systematically,  and  carry- 
ing the  geographical  individual  through  a  determinate  sequence 
of  changes  nearly  as  definite  as  that  passed  through  by  any 
animal  or  plant  in  its  life  development,  but  more  complicated 
from  the  combination  of  the  records  of  several  cycles  of  life 
often  being  found  in  one  individual.  Let  him  learn  that  every 
feature  of  a  geographical  individual  is  significant  and  expressive, 
full  of  meaning  t6  those  who  look  at  it  aright.  Do  not  hesitate 
to  call  on  geological  processes  when  they  are  needed  to  aid  his 
understanding ;  do  not  postpone  the  few  necessary  and  simple 
geological  conceptions  until  he  reaches  a  geological  course  of 
study.  Do  not  be  discouraged  because  the  earth's  surface  contains 
many  complicated  individuals  ;  there  are  many  simple  ones  also, 
which  a  student  may  appreciate  and  enjoy,  and  from  which, 
when  thus  understood,  he  may  form  a  better  idea  of  unseen 
regions.  Of  course  there  are  many  complicated  forms  that  he 
will  not  easily  comprehend  ;  but  so  there  are  plants  of  difficult 
analysis,  yet  this  is  not  held  to  be  an  excuse  for  giving  up  the 
teaching  of  systematic  botany.  Few  scholars  may  be  able  to 
analyze  all  the  Composite,  or  to  recognize  all  the  species  of 
oaks,  even  if  they  have  learned  their  lessons  well  in  school,  and 
yet  we  do  not  doubt  that  there  is  profit  in  the  teaching  of  sys- 
tematic botany.  So  there  may  be  in  teaching  the  elements  of 
systematic  geography.  Let  the  scholar  learn  a  few  simple  forms 
well,  as  he  surely  can  without  difficulty  ;  he  will  recognize  these 
when  he  sees  them,  and  finding  meaning  in  their  form,  he  will 
be  convinced  that  there  is  meaning  also  in  the  more  complicated 
forms  that  his  slight  study  has  not  deciphered.  He  may  even 
come  to  conceive  that  he  has  not  "finished"  geography,  and 
that  it  is  capable  of  advanced  study  for  its  own  sake. 


XI 

PRACTICAL  EXERCISES  IN  PHYSICAL 
GEOGRAPHY 

I 

There  is  coming  to  be  a  general  recognition  that  physical 
geography  must  not  be  taught  by  recitations  alone  ;  that  labora- 
tory and  field  work  should  be  systematically  developed  for  the 
better  understanding  of  the  principles  and  examples  set  forth  in 
the  text ;  and  that  a  proper  assignment  of  space  in  the  school 
building  and  of  time  in  the  school  curriculum  should  be  made 
for  the  accomplishment  of  these  practical  exercises.  There  is  a 
growing  movement  in  favor  of  practical  exercises  :  a  movement 
whose  strength  is  to  be  measured  not  by  the  number  of  teachers 
who  are  standing  still,  indifferent  to  this  innovation  on  traditional 
methods,  but  by  the  number  and  character  of  the  teachers  who 
are  striving,  often  against  difficulties  and  discouragements,  to 
promote  the  rational  development  of  their  subject.  There  was  a 
time,  only  ten  or  fifteen  years  ago,  when  a  "  geographical  labora- 
tory," as  the  name  for  a  room  specially  set  apart  and  equipped 
for  practical  exercises  in  geography,  had  no  place  in  the  school 
arcnitect's  plans ;  but  if  one  may  judge  from  the  amount  of 
inquiry  and  correspondence  as  to  what  a  geographical  laboratory 
should  be  and  as  to  what  it  should  contain,  such  a  time  is  pass- 
ing by.  Let  me  then  devote  this  essay  to  certain  considerations 
regarding  practical  exercises  in  physical  geography,  in  the  hope 
that  my  suggestions  may  find  some  application  in  the  construc- 
tion of  new  school  buildings,  as  well  as  in  the  remodeling  of  old 
ones,  in  the  arrangement  of  new  school  courses,  and  in  the  ap- 
pointment of  new  school-teachers. 

First,  as  to  the  place  in  which  practical  exercises  are  to  be  car- 
ried on.  An  ordinary  schoolroom,  fitted  with  desks  of  the  usual 
size,  one  for  every  pupil,  is  unsatisfactory  in  not  affording  proper 

210 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  211 

accommodation  for  the  maps  and  models  which  the  pupils  are  to 
study,  describe,  or  copy.  Broad  tables  near  good-sized  windows, 
and  movable  or  suspended  racks,  are  well-nigh  indispensable. 
Hence  the  importance  of  having  a  room  specially  set  apart  for 
work  of  this  kind,  a  laboratory  in  which  dust-proof  racks,  cases, 
and  closets  give  convenient  storage  for  materials  not  in  use,  a 
laboratory  adjoining  the  class  room  in  which  recitations  and  lec- 
tures on  geography  are  given.  The  laboratory  need  not  be  so  large 
as  to  contain  table  space  for  an  entire  class,  for  the  class  may  to 
advantage  do  much  laboratory  work  in  small  sections  —  indeed, 
if  no  special  laboratory  is  provided,  the  enterprising  teacher  will 
do  all  he  can  on  ordinary  desks,  but  it  is  a  pity  to  hamper  good 
work  by  unfavorable  conditions.  A  combination  of  class  room 
and  laboratory  is  practicable  in  schools  of  moderate  size,  but  in 
large  schools  a  geographical  laboratory  is  as  important  as  a  phys- 
ical laboratory,  and  in  the  modern  school  buildings,  where  so 
much  consideration  is  given  to  every  need  of  the  teacher,  the 
geographical  laboratory  is,  we  are  glad  to  say,  coming  to  be 
included  in  the  architect's  plans. 

The  practical  teaching  of  geography  needs  furthermore  a  flat 
space  on  the  roof  for  observation  of  the  sky,  a  basement  room 
where  experimental  illustrations  of  land  and  water  may  be  made 
without  danger  of  injuring  the  ceiling  of  a  room  below,  and  a 
reservation  in  the  school  yard  where  a  meridian  line  may  be 
marked  and  various  outdoor  exercises  may  be  carried  on.  It 
needs  also  a  field  for  outdoor  work,  and  this  is,  fortunately,  al- 
ways at  hand  without  expense  to  the  school  committee  ;  it  is 
curious  to  note  how  generally  the  school-teachers'  needs  are 
now  served  by  electric  railways,  which  so  greatly  reduce  the 
difficulty  of  transportation. 

Let  us  next  consider  the  subdivision  of  practical  exercises  as 
to  kind.  It  is  desirable  that  this  part  of  the  work  in  a  course  on 
physical  geography  in  the  high  school  should  be  closely  parallel 
with  the  book  work,  for  the  reason  that  the  main  outline  of  the 
subject  is  best  presented  definitely  and  specifically  in  printed 
form ;  but  it  must  be  recognized  that  many  obstacles  stand  in 
the  way  of  the  easy  attainment  of  this  ideal.  In  the  first  place, 
exercises  on  certain  subjects  must  be  very  deliberately  carried 


212  EDUCATIONAL  ESSAYS 

on,  requiring  even  a  whole  school  year  for  their  proper  inductive 
development.  These  must  either  anticipate  the  high-school  course, 
or  they  must  advance  independently  of  the  text  in  which  their 
equivalent  is  stated  in  printed  form.  The  study  of  the  weather 
finds  some  of  its  best  applications  in  observation  of  storms  and 
other  special  conditions  at  the  time  of  their  occurrence.  These 
must  be  taken  up  in  the  order  of  their  happening,  and  reference 
must  then  be  made  forward  or  back  to  their  systematic  treat- 
ment. Our  climate  is  such  that  the  open-field  season  comes  in 
the  fall  and  spring,  while  many  topics  under  the  important  head- 
ing of  land  forms  will  often  be  taught  from  the  book  in  the  win- 
ter, when  field  work  is  difficult  or  impossible.  Indeed,  even  in 
fall  and  spring,  an  excursion,  well  planned  to  illustrate  the  text 
in  hand  at  the  moment,  may  have  to  be  postponed  on  account  of 
bad  weather,  thus  disorganizing  our  best  intentions.  It  is  true 
that  laboratory  work  may  often  supplement  or  replace  field 
work,  but  not  sufficiently  to  smooth  out  all  the  difficulties  noted 
above.  Simple  parallelism  between  text  and  practical  exercises 
is  therefore  out  of  the  question,  and  we  must  be  content  if  some 
effective  correlation  between  the  two  is  gained  instead. 

In  general,  however,  the  classification  adopted  should  follow 
that  of  the  text-book  in  use  in  the  school ;  as  a  rule  it  will  con- 
tain four  chief  groups,  —  the  earth  as  a  globe,  the  atmosphere, 
the  oceans,  and  the  lands.  To  these  four  some  would  add  human 
conditions  as  a  fifth,  but  my  preference  is  to  distribute  this  sub- 
ject over  all  the  others,  so  that  it  shall  never  be  separated  from 
them  in  the  minds  of  the  pupils.  Latitude  w.ould  then  be  taught, 
not  as  an  abstract  mathematical  problem,  but  as  an  ingenious 
and  practical  device  which  man  uses  in  order  to  indicate  his  place 
with  respect  to  poles  and  equator.  The  sea-bottom  would  then 
be  described  not  merely  as  a  dark,  cold,  quiet,  monotonous  plain, 
but  as  a  contrast  to  the  light  and  dark,  cold  and  warm,  quiet  and 
active,  ever-changing  surface  of  the  land  on  which  is  found  that 
variety  which  even  poets  recognize  as  the  very  spice  of  life,  and 
which  biologists  recognize  as  the  inspiring  cause  of  all  its  higher 
growths,  culminating  in  the  development  of  man  himself.  It  is, 
however,  not  necessary  to  give  more  space  here  to  determine 
whether  the  classification  shall  be  fourfold  or  fivefold,  but  it  is 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  213 

worth  while  to  point  out  that  the  exercises  devoted  to  the  several 
groups  differ  very  widely  in  character.  The  earth  as  a  globe 
must  be  dealt  with  geometrically ;  if  formal  geometry  has  not 
been  studied  by  the  class  in  physical  geography,  let  the  work  pro- 
ceed by  inspectional  geometry.  The  variety  of  work  here  pro- 
vided is  greater  than  is  usually  supposed,  and  is  by  no  means 
dry  or  uninteresting  or  abstract.  Some  practical  suggestions  as 
to  its  character  may  be  found  in  the  latter  portion  of  this  essay. 
Let  me  specially  urge  on  the  attention  of  those  who  are  attracted 
by  this  division  of  the  subject  the  exercises  by  which  latitude, 
longitude,  the  length  of  the  year,  the  obliquity  of  the  ecliptic, 
and  the  declination  of  the  sun  are  determined  by  the  scholars 
themselves,  without  assistance  from  nautical  almanacs  or  other 
external  aids.  No  high  degree  of  accuracy  may  be  reached,  but 
a  real  comprehension  of  these  problems  and  their  applications 
may  be  gained,  such  as  is  never  acquired  by  text-book  study. 

The  atmosphere  must  be  dealt  with  physically.  If  the  class 
has  not  already  studied  physics,  let  them  get  a  good  introduction 
to  its  nature  by  the  measurement  of  temperature,  rainfall,  and 
other  climatic  elements  ;  but  in  the  absence  of  a  good  physical 
basis,  do  not  attempt  to  explain  such  problems  as  the  general 
circulation  of  the  atmosphere ;  that  is  impossible.  Practical  ex- 
ercises on  the  atmosphere  naturally  lead  to  the  construction  and 
study  of  the  weather  maps  with  which  this  country  is  so  highly 
favored  ;  climatic  charts  are  also  susceptible  of  much  more  prac- 
tical and  useful  study  than  is  ordinarily  given  to  them. 

The  study  of  the  ocean  is  both  physical  and  geometric.  This 
part  of  the  subject  should  be  handled  with  a  light  touch ;  it  is 
not  worth  while  to  give  elaborate  attention  to  the  ocean  in  inland 
schools,  but,  if  time  is  allowed,  depths,  waves,  currents,  and 
tides  all  afford  excellent  material  for  practical  exercises  by  which 
useful  lessons  may  be  impressed.  A  tank  in  the  basement  may 
here  be  employed  to  advantage. 

The  study  of  the  lands  must  be  of  a  kind  that  will  lead  pupils 
to  understand  what  they  see  in  a  landscape.  For  this  reason,  con- 
tinents, mountain  ranges,  and  plateaus  are  too  large  to  serve  as 
units.  The  items  that  are  studied  must  be  small  enough  to  be 
seen,  for  it  is  only  by  putting  together  visible  units  that  a  good 


214  EDUCATIONAL  ESSAYS 

idea  of  larger  areas  can  be  gained.  The  units  must  be  studied 
rationally ;  shown  to  be  the  product  of  ordinary  processes,  not 
ready-made  articles  or  the  results  of  a  mysterious  past.  All  exer- 
cises on  land  forms  should  be  directed  to  this  reasonable  end, 
not  only  for  the  sake  of  impressing  a  great  truth  regarding  physio- 
graphic development,  but  still  more  for  the  sake  of  enabling  the 
pupils  to  see  things  better.  There  can  be-  no  question  whatever 
that  observation  is  aided  by  intelligent  understanding.  Much  of 
this  part  of  the  work,  indoors  and  out,  must  be  of  a  nature  that 
is  by  many  called  geological,  though  it  is  not  altogether  clear  why 
geographers  are  so  generally  content  to  leave  to  geologists  all 
treatment  of  matters  so  eminently  physiographic  as  the  weather- 
ing of  rocks,  the  wasting  of  soils,  the  transportation  of  land  waste 
by  streams,  the  abrasion  of  land  margins  by  sea  waves.  If  these 
activities  had  occurred  only  in  the  remote  past,  geologists  alone 
might  lay  claim  to  them,  but,  as  a  matter  of  fact,  they  are  all 
part  of  the  very  living  present.  A  geographer  might  almost  as 
well  be  ignorant  of  the  downstream  direction  of  river  flow  as  of 
the  downstream  transportation  of  land  waste.  From  the  very 
first  teaching  of  geography,  the  young  pupil  should  regard  a 
river  as  the  discharge  of  the  water  and  the  waste  of  its  drainage 
basin,  not  of  pure  water  alone,  though  the  ordinary  definitions 
might  give  him  that  idea.  It  is  chiefly  in  this  connection  that 
field  work  is  so  useful.  Children  may  naturally  enough  believe 
that  weathering  and  erosion  take  place  only  in  books,  if  they  are 
never  led  to  see  the  commonplace  operations  of  these  processes 
in  the  home  field.  They  may  reasonably  infer  that  the  physio- 
graphic development  of  land  forms  is  an  abstraction,  if  they  are 
never  shown  the  results  of  such  development  in  the  hills  and 
valleys  about  their  home.  All  the  habitual  activities  of  the  lands 
should  be  studied  outdoors.  Further  illustration  of  certain  proc- 
esses should  be  given  in  the  school  basement  or  the  school  yard 
with  clay  or  sand  and  a  hose.  Maps,  models,  and  pictures  of  the 
land  forms  that  have  been  fashioned  by  these  processes,  as  well 
as  the  briefest  series  of  minerals  and  rocks  that  chiefly  make  up 
the  lands,  may  be  studied  in  the  laboratory. 

A  well-founded  belief  in  the  reality  of  geographical  facts  is 
one  of  the  smallest  of  the  good  results  that  follow  from  the 


EXERCISES  IN  PHYSICAL  GEOGRAPHY    •         215 

performance  of  field  and  laboratory  work  as  contrasted  with  reci- 
tations from  a  text.  Greater  and  better  results  are  the  development 
of  an  intelligent  self-confidence  in  the  place  of  a  too  docile  submis- 
sion to  a  printed  statement  ;  the  discovery  by  a  young  pupil  that 
he  or  she  is,  like  the  author  of  the  text-book,  a  reasoning  being, 
capable  of  finding  out  things  by  looking  and  thinking  as  well  as 
by  reading ;  above  all,  the  formation  of  a  habit  of  appeal  to  the 
facts  of  nature  by  direct  observation  in  order  to  lay  the  founda- 
tions of  science,  and  of  appeal  to  reason  in  order  to  find  out  the 
meaning  of  the  facts.  If  the  study  of  geography  is  to  serve  for 
the  education  of  something  more  than  post-office  clerks  and  ex- 
press messengers,  if  it  is  to  contribute  a  proper  share  toward  the 
development  of  intelligent  citizens,  then  the  attention  that  is 
now  sometimes  given  to  the  names  of  the  counties  along  the 
southern  or  eastern  boundary  of  a  state  should  be  relaxed,  and 
fuller  attention  be  given  to  the  observation  of  facts  that  have  a 
more  enlarging  interest  and  application. 

Though  it  is  physical  geography  in  the  high  school  that  here 
takes  our  attention,  it  should  not  be  forgotten  that  many  exer- 
cises of  a  practical  nature  should  be  given  in  the  lower  schools. 
The  observational  determination  of  the  length  of  the  year,  of  the 
mean  temperature  of  a  month,  and  of  the  weathering  and  washing 
of  land  waste  ought  to  be  made  before  the  high  school  is  reached. 
Then  the  pupil  in  the  high  school  can  do  something  better ;  for 
example,  he  can  by  observation  and  correspondence  determine 
the  difference  of  longitude  between  his  school  and  some  other 
school ;  he  can  similarly  measure  the  size  of  the  earth,  measure 
the  inversions  of  temperature  that  occur  during  anti-cyclonic 
winter  weather,  discuss  the  development  of  land  forms  as  affected 
by  the  wasting  and  washing  of  their  rocks.  Before  a  satisfac- 
tory scheme  of  high-school  exercises  can  be  planned,  appropriate 
schemes  for  the  lower  schools  must  be  adopted  ;  and  if  this  state 
association  desires  a  useful  task  for  some  of  its  members,  let  a 
committee  be  appointed  for  the  more  precise  formulation  of  the 
physiographic  work  that  ought  to  be  done  in  successive  school 
years.  Let  me  counsel  such  a  committee  to  be  ambitious  and 
not  to  content  itself  with  recommendations  that  can  be  immedi- 
ately carried  out,  but  rather  with  such  as  will  call  for  some  effort 


2l6  EDUCATIONAL  ESSAYS 

on  the  part  of  the  average  teacher.  Let  us  compare  notes  on  the 
results  of  such  efforts  ten  years  hence.  In  the  meantime,  it  is 
evident  that  much  educational  waste  can  be  stopped  by  a  well- 
arranged  scheme  of  work  for  successive  years.  Each  year  should 
include  the  work  best  adapted  to  it ;  older  pupils  will  then  not 
have  to  do  elementary  exercises.  The  work  of  each  year  will  be 
usefully  built  on  by  the  work  of  late  years ;  it  will  thus  be  kept 
as  fresh  as  possible  in  the  pupil's  memory.  No  work  will  be  un- 
necessarily repeated,  and  valuable  scraps  of  time  will  be  gained 
in  an  economy  of  this  kind.  Coordinated  work  is  as  important  in 
practical  physiographic  exercises  as  it  is  in  arithmetic,  algebra, 
and  geometry. 

An  important  question  is  encountered  in  considering  the 
equipment  of  a  high  school  for  good  practical  work  in  physical 
geography.  We  must  all  agree  that  the  first  item  in  the  equip- 
ment, ranking  above  laboratory  and  apparatus,  is  a  good  teacher; 
and  by  a  good  teacher,  I  mean  one  who  has,  among  other  things, 
actually  performed  a  large  variety  of  practical  exercises,  has  really 
learned  what  field  work  means,  and  is  competent  to  explore  a 
new  district  and  to  discover  its  field  resources  in  so  far  as  they 
are  related  to  school-teaching.  If  I  may  judge  from  the  teachers 
who  have  attended  my  summer  course  in  geography  at  Harvard 
University  during  past  years,  such  preparation  is  rare,  because  of 
the  novelty  of  practical  work  in  geography.  There  is  plenty  of 
interest  and  capacity,  but  little  experience  or  confidence.  We 
must  wait  for  about  two  school  generations — about  twenty  years 
—  before  such  preparation  will  be  general,  and  we  may  not  al- 
ways find  it  even  then.  The  best  thing  to  do  now  is  to  give  ex- 
isting teachers  every  chance  to  improve  themselves,  and  to  give 
intending  teachers  every  encouragement  to  make  serious  prep- 
aration for  their  future  work. 

The  material  equipment  of  a  physiographic  laboratory  is  to- 
day under  active  discussion.  There  is  no  standard  equipment 
yet  devised.  There  is  at  present  no  school-furnishing  firm  ready 
to  supply  a  complete  set  of  materials,  all  prepared,  leaving  the 
teacher  only  to  make  such  additions  as  will  serve  his  individu- 
ality or  his  locality.  Here  is  room  for  enterprise.  In  the  mean- 
time, we  should  all  expect  to  find  globes  and  wall  maps  in  a 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  217 

geographical  laboratory  or  class  room  ;  it  is  now  coming  to  be 
customary  to  find  also  certain  large-scale  maps,  such  as  are 
published  by  our  government  bureaus,  and  an  occasional 
model ;  but  when  it  comes  to  details,  it  is  evident  that  the 
practical  exercises. must  be  first  planned,  and  the  materials  for 
their  accomplishment  must  then  be  secured.  Your  proposed 
committee  has  therefore  a  double  task,  —  first,  to  devise  the 
exercises,  and  second,  to  devise  appropriate  materials  for  per- 
forming them. 

Before  closing  I  wish  to  consider  some  of  the  external  con- 
ditions that  will  help  or  hinder  the  attainment  of  our  ideals. 
Foremost  here  is  the  responsibility  of  the  normal  schools.  It 
will  be  at  once  admitted  that  an  energetic  normal  teacher  of 
physiography,  well  trained  in  his  subject,  imbued  with  the 
scientific  spirit  and  possessing  the  teaching  instinct,  may 
greatly  promote  the  progress  that  we  have  at  heart ;  all  the 
more,  if  he  is  sympathetically  sustained  by  the  principal  of  the 
school  to  the  point  of  gaining  a  good  material  equipment.  But 
I  fancy  that  one  of  the  great  discouragements  that  such  a 
teacher  suffers  is  the  ease  with  which  normal  graduates  im- 
perfectly prepared  in  physical  geography  secure  positions  in 
our  schools.  Hence  we  must  look  next  to  the  superintendents 
or  other  appointing  powers,  and  urge  them  to  require  of  a 
candidate  as  high  a  degree  of  proficiency  in  physical  geography 
as  in  any  other  subject ;  or,  still  better,  to  require  a  specializa- 
tion in  physical  geography  of  any  one  to  whose  hands  this 
growing  subject  is  to  be  intrusted  in  high  schools  and  academies. 
A  conference  among  normal  teachers,  superintendents,  and  mas- 
ters, to  determine  what  shall  be  done  in  the  school  courses  in 
physiography,  and  what  preparation  shall  be  expected  of  new 
teachers  during  the  next  five  years,  would  be  of  value  if  it  re- 
sulted in  raising  the  present  standards ;  but  it  would  be  a  hin- 
drance if  it  gave  authoritative  approval  to  the  unsatisfactory 
conditions  now  existing  and  took  no  steps  to  better  them. 

An  effective  external  aid  to  observational  teaching  is  the  prep- 
aration of  local  guidebooks  for  field  work.  The  physiographic 
resources  of  many  districts  cannot  at  present  be  so  well  set 
forth  by  school-teachers  as  by  experts  of  a  larger  experience. 


2l8  EDUCATIONAL  ESSAYS 

Lectures  and  excursions  for  teachers,  such  as  are  often  given 
by  university  professors  of  geology,  are  very  helpful,  but  their 
value  would  be  increased  if  they  could  be  set  forth  in  printed 
form  with  due  regard  to  their  actual  use  in  schools.  For  the 
object  here  considered,  it  is  not  enough  that  a  local  guidebook 
shall  present  an  accurate  account  of  the  home  district ;  the 
account  should  be  presented  in  the  order  in  which  it  will  be 
used  in  the  schools,  so  that  it  will  serve  as  an  immediate  aid  in 
school-teaching.  Local  scientific  societies  could  do  excellent 
work  in  supporting  the  publication  of  such  guidebooks,  and 
thus  they  would  greatly  promote  their  own  success  in  a  later 
generation  of  members. 

II 

In  order  to  give  specific  indication  of  the  character  of  various 
practical  exercises  and  of  the  correlations  that  may  be  established 
between  such  exercises  and  bookwork,  the  second  part  of  this 
essay  may  be  devoted  to  a  presentation  of  some  examples  ap- 
propriate to  the  study  of  that  interesting  chapter  of  physical 
geography  which  is  often  given  a  forbidding  appearance  under 
the  name  of  "  mathematical  geography." 

The  Earth  as  a  Globe.  It  is  seldom  that  justice  is  done  to  the 
opportunity  for  practical  work  under  the  heading  of  "  the  earth 
as  a  globe."  The  difficulties  that  stand  in  the  way  of  various 
observational  exercises  may  certainly  be  overcome  if  their  ac- 
complishment rather  than  the  maintenance  of  a  set  order  of 
school  periods  is  made  the  object  in  view.  Many  series  of  ob- 
servations that  cannot  and  need  not  be  made  by  a  whole  class 
may  be  made  by  scholars  singly  or  in  pairs ;  the  avoidance  of 
such  exercises,  because  of  the  disorder  that  they  may  create, 
does  not  speak  well  for  the  discipline  or  for  the  spirit  of  the 
school.  Several  of  these  exercises  are  best  performed  under  the 
name  of  nature  study  in  lower  grades  than  the  high  school ;  they 
are  mentioned  here  because  if,  as  is  too  often  the  case,  they  have 
not  been  performed  in  their  proper  place,  they  should  be  given 
place  in  the  high  school;  but  it  is  manifest  that  such  a  plan  dis- 
arranges the  high- school  course  in  physical  geography  and  retards 
the  attainment  of  the  grade  that  it  deserves. 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  219 

Shape  of  the  Earth.  The  only  observational  proof  of  the 
globular  shape  of  the  earth  that  is  within  the  reach  of  young 
scholars  is  offered  at  the  time  of  an  eclipse  of  the  moon.  Such 
an  opportunity  should  not  be  lost  sight  of.  The  edge  of  the 
earth's  shadow  always  having  a  curved  outline,  the  earth  must 
be  round,  as  Aristotle  perceived  four  centuries  before  the 
Christian  era.  The  time-honored  proof  afforded  by  the  gradual 
disappearance  of  ships  at  sea  is  available  only  at  the  seashore  ; 
it  is  interesting  to  note  that  this  proof  was  first  mentioned  by 
Strabo.  Accepting  the  globular  form  as  a  fact,  the  horizon 
plane,  touching  the  earth's  surface  at  the  observer's  station, 
extends  indefinitely  on  all  sides  —  the  visible  sky  lying  above, 
the  invisible  sky  lying  below,  the  plane.  As  long  as  the  earth 
is  thought  of  as  a  large  body  in  comparison  to  the  dimensions 
of  the  sky  vault,  it  will  probably  be  more  or  less  consciously 
believed  that  the  smaller  half  of  the  sky  is  above,  and  the  larger 
part  is  below,  the  horizon  of  an  observer.  But  when  the  earth 
is  stated  to  be  very  small  in  comparison  to  the  distance  to  the 
stars,  the  two  parts  of  the  sky  separated  by  a  horizon  plane  will 
be  recognized  as  equal.  The  horizon  planes  of  observers  at  dif- 
ferent points  on  the  earth  will  cut  the  sky  into  different  halves, 
as  may  be  shown  by  the  aid  of  a  hand  globe.  The  uneven  border 
of  the  sky  against  hills  should  be  called  the  sky  line,  not  the 
horizon.  All  this  is  as  much  astronomy  as  geography,  but  it  is 
all  essential  to  the  clear  understanding  of  matters  that  are  con- 
stantly taught  in  geography,  such  as  latitude  and  the  seasons ; 
no  safe  entrance  into  such  matters  can  be  made  without  careful 
attention  to  fundamental  concepts. 

The  discovery,  attributed  to  Eudoxus,  that  an  observer  trav- 
eling north  or  south  sees  that  stars  change  their  position  with 
respect  to  his  horizon,  will  be  considered  in  connection  with 
measures  of  the  size  of  the  earth  further  on. 

The  causes  and  consequences  of  the  earth's  shape  are  better 
presented  in  the  text  than  in  practical  exercises.  Among  the 
consequences  are  the  essentially  uniform  value  of  gravity  at  all 
points  on  the  earth's  surface,  and  the  absence  of  immense  ascents 
and  descents  that  must  occur  on  an  earth  of  any  other  shape. 
The  nearly  globular  form  of  the  actual  earth  has  been  of 


220  EDUCATIONAL  ESSAYS 

enormous  importance  during  long-past  ages  in  facilitating  the 
migration  of  plants  and  animals  from  one  region  to  another, 
and  in  recent  centuries  in  permitting  the  migrations  of  man- 
kind and  the  development  of  commerce. 

Rotation.  The  vague  ideas  in  the  minds  of  adults  regarding 
the  earth  as  a  rotating  globe  suggest  that  no  good  ground  was 
provided  in  their  school  days  for  a  correct  understanding  of  this 
fundamental  problem.  The  problem  pertains  equally  to  geogra- 
phy and  to  astronomy  ;  but  as  it  should  be  encountered  before 
these  two  subjects  are  differentiated,  it  is  naturally  classified 
under  the  first  and  more  usual  school  subject.  Very  simple  ap- 
paratus suffices.  A  pointer,  pivoted  at  one  end  and  sighted  at 
the  sun  at  different  hours  through  the  day,  enables  a  young 
observer  to  gain  a  definite  idea  of  the  sun's  (apparent)  daily 
movement  across  the  sky.  (Actual  sighting  at  the  sun  is  not 
necessary  ;  when  the  pointer  is  held  so  that  its  shadow  is  no 
larger  than  its  cross  section,  it  is  properly  directed.)  Record  of 
successive  observations  may  be  made  by  setting  up  stakes  so 
that  their  tops  shall  just  touch  the  end  of  the  pointer  in  the  suc- 
cessive sights  at  the  sun.  On  the  following  day  the  sun  may  be 
seen  again  in  the  earliest  position  observed  on  the  first  day,  the 
period  thus  measured  being  a  natural  unit  of  time  which  civilized 
nations  divide  into  twenty-four  hours.  It  is  important  to  notice 
that  the  sun's  return  to  its  original  position  has  not  been  accom- 
plished by  going  backward,  but  by  continuous  motion,  as  if  in  a 
circuit.  The  idea  of  rotation  is  thus  clearly  presented  in  spite 
of  the  fact  that  much  of  the  sun's  diurnal  path  is  out  of  sight. 
It  should  not  be  understood  that  these  observations  give  school 
children  their  first  knowledge  of  the  movement  of  the  sun  in  the 
sky  ;  that  they  have  long  known.  But  the  vagueness  of  ordinary 
knowledge  on  this  point  is  now  advanced  to  well-defined  knowl- 
edge, and  this  is  an  important  step. 

Regularity  in  the  movement  of  rotation  is  easily  shown  by 
making  observations  at  regular  intervals  of  one  or  two  hours  and 
noting  that  equal  angles  are  moved  over  by  the  pointer,  or  that 
equal  arcs  are  measured  between  the  stake  tops  in  equal  time 
intervals.  It  is,  I  believe,  well  understood  by  teachers  to-day 
that  no  preparatory  study  of  formal  geometry  is  needed  as  a 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  221 

basis  for  inspectional  geometry  of  this  kind.  A  little  more  ad- 
vanced treatment  is  given  by  making  observations  at  irregular 
periods,  noting  the  time  intervals  between  them,  and  proving 
by  a  continued  proportion  that  angles  and  times  bear  a  constant 
ratio.  The  angle  of  complete  rotation  (360°)  will  be  found  to 
bear  the  same  ratio  to  the  time  of  a  complete  rotation  (twenty- 
four  hours)  as  that  which  obtains  between  partial  angles  and 
times ;  hence  the  movement  of  the  sun  while  it  is  beneath  the 
horizon  must  be  at  the  same  angular  velocity  as  while  it  is  within 
reach  of  observation  above  the  horizon.  Daytime  observations 
of  the  old  moon  (about  third  quarter)  and  evening  observations 
of  stars  at  home  may  be  used  to  extend  the  results  gained  from 
the  observations  of  the  sun.  If  the  moon  is  studied,  the  teacher 
should  be  prepared  to  explain  the  questions  that  may  arise  if  the 
difference  in  length  of  solar  and  lunar  days  is  detected.  The 
chief  point  to  be  determined  by  star  observation  is  that  a  star 
must  make  a  circuit  of  the  sky  in  about  twenty-four  hours,  be- 
cause on  the  second  evening  it  comes  from  the  eastward  to  the 
position  from  which  it  departed  with  a  westward  motion  the 
night  before,  —  an  elementary  matter  truly,  but  one  which  is 
less  clearly  known  to  many  civilized  adults  than  it  was  to  their 
barbarous  ancestors. 

Axis  and  Meridians.  As  a  result  of  these  observations  it  is 
recognized  that  "  something  "  must  turn.  Whether  it  is  the  earth 
or  the  sky  that  turns  need  not  be  decided  at  once,  if  the  teacher 
has  the  patience  to  let  this  archaic  problem  really  take  posses- 
sion of  the  pupils'  minds.  In  either  case,  the  fact  of  turning 
demands  an  axis  on  which  the  turning  shall  take  place,  and  if 
the  pupils  have  any  serious  difficulty  in  discovering  and  stating 
the  attitude  of  the  axis,  the  teacher  may  be  sure  that  the  diffi- 
culty lies  chiefly  in  the  form  of  her  questions,  for  the  problem  is 
essentially  easy  to  living  boys  and  girls,  however  difficult  it  may 
seem  when  clothed  in  words  to  which  they  are  not  accustomed. 
When  the  "slanting"  attitude  of  the  axis  of  turning  is  clearly 
recognized,  all  problems  of  size, latitude,  and  longitude  are  greatly 
simplified.  By  whatever  short  cut  the  teacher  presents  the  con- 
clysion  that  the  earth  and  not  the  sky  really  turns,  the  axis  must 
be  conceived  as  passing  through  the  earth's  center,  and  as 


222  EDUCATIONAL  ESSAYS 

defining  two  significant  points,  the  poles,  where  it  "comes  out." 
The  discovery  of  the  north  pole  of  the  sky  near  the  north  star 
(really  more  than  two  moon  diameters  from  it  toward  the  end  of 
the  Dipper  handle)  leads  to  a  clearer  understanding  of  the  diur- 
nal paths  of  the  stars  in  smaller  or  larger  circles. 

The  shadow  cast  by  a  vertical  pole  on  level  ground  by  the 
midday  sun  shows  us  the  direction  in  which  one  must  travel  to 
reach  the  north  pole.  The  prolongation  of  this  line  around  the 
earth  gives  a  meridian  circle.  The  meridians  are  standard  lines 
of  direction.  The  equator  is  the  great  circle  that  cuts  all  the 
meridians  in  halves,  midway  between  the  poles.  A  series  of  me- 
ridians drawn  at  equal  distances  apart  at  the  equator  divide  the 
earth  into  equal  areas,  conveniently  arranged  for  measuring  the 
relative  easting  or  westing  of  places.  A  small  hand  globe  may 
be  appealed  to  in  this  connection,  but  constant  reference  should 
be  made  to  "  outdoors  "  as  a  part  of  the  real  earth  on«whose  sur- 
face the  imaginary  circles  are  to  be  traced.  "  There  "  on  a  hand 
globe  is  not  so  useful  as  "  there,"  pointing  out  the  window  toward 
the  equator.  The  latter  may  arouse  a  live  sense  of  directions, 
always  useful  in  self -orientation,  whatever  is  one's  path  in  life ; 
the  former  may  leave  the  subject  an  unreality. 

Latitude.  The  determination  of  local  solar  time  and  of  mag- 
netic variation  may  be  introduced  in  this  connection,  but  more 
important  is  the  estimation  of  one's  position  on  the  earth's  sur- 
face with  respect  to  the  pole  and  equator.  No  mention  of  the 
term  "latitude"  need  be  made  till  this  question  is  solved.  It 
may  be  solved  even  in  the  grammar  school  by  means  of  the  sun 
circle,  marked  out  by  stake  tops,  as  above  described.  First, 
some  general  considerations.  To  an  observer  at  the  pole  the  sun 
or  the  stars  would  travel  around  the  sky  once  a  day,  in  circles 
parallel  to  the  horizon.  The  position  of  the  star  circles  remains 
fixed  wherever  the  observer  goes  and  however  much  his  horizon 
changes  from  the  position  that  it  had  at  the  pole.  As  the  ob- 
server moves  along  any  meridian  toward  the  equator  his  horizon 
must  progressively  tilt  from  the  position  that  it  had  at  the  pole, 
and  the  amount  of  tilting  may  be  measured  by  the  angle  between 
the  tilted  horizon  and  any  one  of  the  star  or  sun  circles.  This 
is,  in  essence,  the  method  of  Eudoxus,  already  referred  to.  A 


EXERCISES  IN  PHYSICAL  GEOGRAPHY 


223 


third  way  from  pole  to  equator  the  angle  would  be  30°;  halfway, 
45°;  two-thirds  way,  60°;  at  the  equator,  90°.  The  rotation  of 
the  earth  is  thus  of  great  assistance  in  determining  the  relative 
positions  of  places.  Bearing  these  principles  in  mind,  let  the  sun 
circle  be  determined  and  represented  by  a  series  of  stakes  in  a 
school  yard,  as  in  Fig.  i.  Stand  about  thirty  feet  to  one  side  of 
the  stakes,  in  such  a  position  that  the  tops  of  all  of  them  fall 
into  a  slanting  straight  line  when  the  observer's  head  is  lowered 
to  the  height  of  the  highest  stake  ;  estimate  or  measure  the  angle 
CAD,  by  which  the  horizon  is  depressed  beneath  this  slanting 
line ;  and  as  the  angle  thus  determined  is  to  90°,  so  is  the  dis- 
tance from  the  pole  (measured  along  a  meridian  from  the  pole  to 


-.:;?;:;,....„  ^  .«M»W»  •* 

FIG.  i 

the  observer)  to  the  entire  quadrant  of  the  meridian  from  pole 
to  equator.  Latitude  is  counted  from  the  equator  toward  the 
pole  ;  it  will  therefore  be  the  complement  of  the  angle  just  meas- 
ured. It  should  be  noted  that  latitude  may  be  thus  determined 
at  any  time  of  year  and  without  knowledge  of  the  sun's  angular 
distance  from  the  sky  equator  (declination).  In  order  to  avoid 
misunderstanding,  it  may  be  pointed  out  that  the  pivot  does  not 
lie  in  the  plane  of  the  sun  circle,  and  the  slanting  line  AD  does 
not  measure  the  sun's  noon  altitude,  except  at  the  equinoxes. 
The  noon  altitude  of  the  sun  varies  through  the  year,  but  the 
slanting  line  (the  slant  of  the  plane  of  the  sun  circle)  is  constant 
through  the  year,  whatever  the  declination  of  the  sun.  In  all  this 
method  of  determining  latitude  it  is  assumed  that  the  motion  of 
the  sun  in  declination  in  a  single  day  will  not  be  detected  by  the 
rough  methods  of  record  here  employed. 


224  EDUCATIONAL  ESSAYS 

An  interesting  feature  of  this  elementary  method  of  latitude 
determination  is  its  novelty  to  many  teachers,  It  involves  noth- 
ing that  grammar-school  pupils  who  have  learned  by  seeing  and 
thinking,  not  by  recitation,  cannot  easily  apprehend  if  they  are 
gradually  led  up  to  it  by  a  well-graded  flight  of  steps ;  the  steps 
are  not  difficult  and  the  flight  is  not  long.  The  fear  that  they 
are  so,  on  account  of  which  many  a  teacher  dreads  to  introduce 
fundamental  work  of  this  kind  into  her  teaching,  only  goes  to  show 
the  obscurity  and  confusion  in  which  the  chapter  on  so-called 
"  mathematical  geography"  is  often  enveloped.  Leave  out  this 
forbidding  name,  teach  slowly  on  the  basis  of  gradually  accumu- 
lated observations,  and  the  imagined  difficulties  will  disappear. 

The  determination  of  latitude  by  the  altitude  of  the  pole  star 
should  always  be  preceded  by  a  proof  that  the  star  is  close  to  the 
pole ;  but  even  then  the  sun-circle  method  is  to  be  preferred  as 
being  possible  in  the  daytime.  The  measurement  of  latitude  involv- 
ing the  sun's  declination  should  not  be  introduced  until  the  move- 
ment of  the  sun  in  declination  has  been  followed  and  its  greatest 
northing  and  southing  measured  by  a  simple  method  given  below. 

Size  of  the  Earth.  Nothing  has  yet  been  said  of  the  size  of 
the  earth.  Observations  at  a  single  station  will  not  serve  to 
measure  the  size,  but  the  essence  of  the  method  of  measurement 
may  be  usefully  imitated,  and,  by  correspondence  between  two 
schools,  actual  measurement  may  be  made,  much  to  the  edifica- 
tion of  the  pupils.  The  relations  of  the  local  horizon  to  the  plane 
of  the  sun  circle,  as  involved  in  the  measurement  of  latitude, 
enable  the  scholar  to  "  see,"  if  not  to  demonstrate,  that  an  angle 
of  one  degree  must  separate  the  local  horizons  of  two  stations 
on  the  same  meridian,  whose  latitude  differs  by  one  degree. 
Similarly,  if  observations  of  the  sun's  midday  (meridian)  altitude 
were  made  at  two  such  stations  on  the  same  day,  the  altitudes 
would  differ  by  one  degree.  Then,  measuring  the  distance  along 
the  meridian  arc  between  the  stations,  a  simple  proportion  gives 
the  circumference  of  the  meridian  circle  : 

i°  :  360  : :  length  of  arc  :  circumference. 

This  imitates  the  method  employed  by  Eratosthenes.  Two 
parties  of  scholars  stationed  at  the  ends  of  a  short  meridian 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  225 

arc  in  a  school  yard  or  in  an  adjacent  common  may  each  deter- 
mine the  noon  altitude  of  the  sun  and  measure  the  distance  be- 
tween their  stations  in  imitation  of  the  genuine  method  of  earth 
measurement,  and  they  may  be  convinced  that  if  their  observa- 
tions were  minutely  accurate,  the  size  of  the  earth  could  be  esti- 
mated from  even  so  short  an  arc  as  that  which  they  can  pace 
during  a  recess  interval.  If  a  hill  rises  near  the  school,  the  con- 
vexity of  the  hill  may  be  taken  to  imitate  the  rotundity  of  a  little 
earth.  Two  parties  stationed  out  of  sight  of  each  other  on  the 
north  and  south  slopes  of  the  hill,  and  on  a  north  and  south  line, 
may  determine  the  sun's  noon  altitude  with  reference  to  the 
slopes  of  the  hill  (which  imitate  the  curved,  level  surface  of  a 
little  earth),  and  then,  measuring  the  arc  between  their  stations, 
the  size  of  a  small  earth  to  which  such  a  hill  would  fit  may  be 
determined.  In  the  absence  of  a  hill,  a  useful  substitute  may  be 
provided  in  a  school  yard  by  placing  two  tables  or  boxes  in  a 
north  and  south  line  fifty  or  a  hundred  feet  apart,  tilting  their 
upper  surfaces  away  from  each  other,  and  then  proceeding  on 
the  pretence  that  the  table  surfaces  are  parts  of  a  little  earth, 
whose  convex  meridian  may  be  indicated  by  the  tops  of  a  row 
of  stakes  between  them.  The  curved  surface  of  a  globe  in  a 
schoolroom  may  be  used  to  explain  the  geometry  here  involved, 
but  outdoor  work  should  not  be  altogether  replaced  by  such  in- 
door substitutes.  Nothing  can  so  well  give  the  sense  of  the  real 
great  earth  as  outdoor  observations. 

Two  schools  can  profitably  cooperate  to  measure  the  size  of 
the  earth.  On  a  certain  day  agreed  upon  beforehand  the  midday 
altitude  of  the  sun  is  determined  at  each  school.  The  length  of 
the  meridian  arc  between  the  latitude  circles  of  the  two  schools 
may  then  be  measured  on  a  good  map  and  the  proportion  of 
Eratosthenes  again  employed  to  find  the  unknown  quantity.  If 
each  school  determines  its  own  latitude,  the  difference  of  lati- 
tudes replaces  the  difference  of  the  sun's  midday  altitude  on  a 
given  day,  and  then  no  agreement  as  to  the  day  of  observation 
is  necessary.  Why  is  it  that  nature  study  of  this  kind,  so  appro- 
priate to  the  inhabitants  of  a  rotating  globe,  is  not  introduced 
in  our  lower  schools  ?  Is  it  because  of  the  supposed  difficulty  or 
the  actual  simplicity  of  the  necessary  observations ;  on  account 


226  EDUCATIONAL  ESSAYS 

of  a  recognition  or  a  neglect  of  their  value  ;  on  account  of  a  con- 
fidence in  the  innate  ability  of  young  scholars  or  a  mistrust  of 
their  powers  ;  or  on  account  of  preparation  or  lack  of  prepara- 
tion on  the  part  of  the  teachers  ?  To  the  best  of  my  belief,  this 
is  merely  one  of  the  many  cases  in  which  the  real  mental  activ- 
ity of  school  children  is  benumbed  by  substituting  recitations  of 
words  for  live  performance. 

Longitude.  Difference  of  longitude  (introduced  under  any 
name  that  is  suggested  by  the  pupils  when  talking  freely  of  the 
relative  positions  of  places  on  a  rotating  globe  —  the  technical 
name  to  come  in  later)  can  be  determined  between  two  schools 
in  any  one  of  the  three  historical  methods.  As  Strabo  employed 
an  eclipse  of  the  moon  to  determine  the  relative  easting  or  west- 
ing of  certain  points  bordering  the  Mediterranean,  so  school 
children  in  different  parts  of  the  country  may  employ  a  lunar 
eclipse  to-day  to  determine  the  relative  positions  of  the  meridians 
on  which  their  homes  are  situated,  previously  determining  their 
local  solar  time,  and  subsequently  comparing  the  recorded  time 
of  any  phase  of  the  eclipse  by  correspondence.  As  governmen- 
tal parties  a  hundred  years  ago  made  chronometer  expeditions 
between  neighboring  national  capitals,  so  school  children  may 
to-day  send  a  watch  from  one  school  to  another  by  express,  and 
thus  make  a  very  good  determination  of  difference  of  longitude. 
As  modern  observers  employ  the  telegraph  for  time  compari- 
sons, even  if  separated  by  the  whole  breadth  of  a  continent  or 
of  an  ocean,  so  school  children  may  to-day  delegate  some  of 
their  number  to  go  to  a  telegraph  office  and  send  "  time  signals  " 
from  their  watch  (previously  set  to  local  solar  time  by  their  own 
observations)  to  an  expectant  party  at  the  other  end  of  the  line. 
The  two  parties  may  have  to  wait  half  an  hour  or  so  to  get  the 
line  "clear,"  but  such  a  trifling  delay  should  be  no  obstacle  to 
success  ;  and  even  such  delay  may  be  avoided  if  a  long-distance 
telephone  is  used  ;  then  the  time  signals  may  be  counted  aloud 
by  one  party  and  directly  heard  by  the  other.  Surely  it  is  not  the 
lack  of  capacity  on  the  part  of  the  pupils  ;  it  is  not  the  expense 
involved  ;  it  is  not  the  difficulty  or  the  uselessness  of  the  work 
that  keeps  such  practical  experiments  as  these  out  of  our  schools. 
What  is  the  real  difficulty  in  the  way  of  their  introduction  ? 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  227 

Indoor  Exercises.  Practical  exercises  of  another  kind  on  the 
earth  as  a  globe  may  be  performed  indoors.  A  meridian  section 
of  the  earth  as  a  sphere  and  as  a  spheroid  may  be  drawn  to 
scale  in  order  to  show  how  vanishingly  insignificant  the  polar 
flattening  really  is.  Geographically,  its  value  is  negligible  in  a 
high-school  course,  however  important  and  interesting  it  is  in 
astronomy  and  however  valuable  it  is  historically  as  a  proof  of 
the  earth's  rotation.  The  height  of  the  highest  mountains,  the 
depth  of  the  deepest  oceans,  the  mean  altitude  of  continents, 
the  mean  depth  of  sea  floors,  and  the  rate  of  increase  of  interior 
temperatures  may  all  be  shown  on  this  earth  section.  Compari- 
sons of  local  and  general  distances  and  heights  may  be  made  by 
drawing  them  to  scale. 

Several  methods  of  map  projection  may  be  illustrated.  First 
the  necessity  for  projection  should  be  shown  by  the  impossibility 
of  smoothly  laying  a  paper,  cut  to  match  a  continental  outline, 
upon  the  surface  of  a  globe.  The  mercator  (or  stovepipe  and 
cannon  ball),  the  conical,  and  the  gnomonic  projections  may  be 
easily  constructed  ;  their  difficulties  may  be  magnified  if  clothed 
jn  mathematical  language,  or  minified  if  talked  about  familiarly. 
After  a  network  of  meridians  and  latitude  circles  is  drawn  out 
a  continental  outline  may  be  platted  from  a  table  giving  the  lati- 
tudes and  longitudes  of  a  number  of  points  on  the  coast  line. 
Greenland  and  South  America  on  Mercator  projection,  Green- 
land on  Mercator  and  conical  projection,  the  margin  of  the  un- 
explored areas  in  the  Arctic  and  Antarctic  regions  on  gnomonic 
projections  all  afford  good  practice  for  platting.  Comparison  of 
distances  on  globes  and  on  maps  serves  to  detect  the  distortion 
characteristic  of  each  kind  of  projection.  A  great-circle  sailing 
course  between  San  Francisco  and  Yokohama,  as  determined 
on  a  globe,  may  be  transferred  to  any  projection  by  the  latitude 
and  longitude  of  a  number  of  points  on  its  path.  The  same  may 
be  tried  on  a  polar  gnomonic  projection  of  the  great  southern 
ocean  for  a  voyage  from  Cape  Horn  to  Tasmania.  The  results 
in  the  "two  cases  are  interesting  and  instructive.  From  my  own 
experience  with  school-teachers  in  problems  of  this  kind,  it  is 
necessary  to  conclude  that  geometry  must,  as  a  rule,  have  been 
very  badly  taught  to  them. 


228  EDUCATIONAL  ESSAYS 

Terrestrial  magnetism  affords  some  interesting  exercises,  if 
time  can  be  allowed  to  them.  The  local  variation  of  the  mag- 
netic needle  has  already  been  determined.  Charts  published  by 
the  Coast  Survey  and  elsewhere  give,  by  means  of  lines  of 
equal  variation,  the  values  of  local  variation  at  any  desired  point. 
Local  values  thus  obtained  may  be  copied  off  on  the  blackboard, 
and  the  pupils  may  then  write  in  the  values  on  a  Mercator  map 
of  the  world  (of  their  own  construction,  if  desired),  or  on  an 
outline  map  of  the  United  States.  The  values  thus  charted 
afford  practice  in  drawing  lines  of  equal  variation.  The  accu- 
racy of  the  work  can  be  tested  by  comparing  the  results  with 
the  original  chart.  A  variation  on  this  exercise  may  be  made 
by  drawing  arrows  at  various  stations  to  represent  the  local 
direction  of  magnetic  north.  Extend  the  arrows,  curving  them, 
if  necessary,  so  that  they  shall  not  cross  each  other ;  they  will 
then  represent  magnetic  meridians.  The  north  magnetic  pole, 
in  the  neighborhood  of  Hudson  bay,  may  be  thus  discovered. 
The  meaning  of  magnetic  charts  can  hardly  be  made  clear 
without  performing  exercises  of  this  kind. 

The  point  that  deserves  special  emphasis  with  regard  to  all. 
the  exercises  thus  far  described  is  not  so  much  their  importance, 
although  all  are  important,  but  rather  their  practicability.  If 
the  shape  and  size  of  the  earth,  latitude  and  longitude,  and  ter- 
restrial magnetism  are  taught  at  all,  practical  exercises  should 
replace  recited  definitions  as  far  as  possible.  In  all  stages  of  the 
work  excellent  practice  in  English  composition  is  afforded  by 
calling  for  written  description  of  observations  and  for  careful 
formulation  of  results. 

The  Atmosphere.  The  study  of  the  atmosphere  suggests  a 
great  variety  of  practical  exercises,  many  of  which  are  now 
familiarly  introduced  in  our  schools.  Local  observations,  with- 
out and  with  instruments,  are  made  and  discussed  systematically. 
They  are  correlated  with  the  larger  phenomena  of  the  weather 
maps,  but  the  work  in  this  direction  often  falls  far  short  of  its 
possible  measure.  In  this  connection  I  may  refer  to  a  book  by 
my  colleague,  R.  De  C.  Ward,  entitled  "  Practical  Exercises  in 
Elementary  Meteorology,"  in  which  the  teacher  and  the  pupil 
will  find  precise  directions  for  the  solution  of  a  large  number 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  229 

of  problems  that  I  am  sure  will  be  of  great  value  in  giving  fuller 
appreciation  of  the  treasures  stored  up  in,  but  not  always  taken 
from,  the  daily  weather  maps.  This  guidebook  being  now  access- 
ible, I  need  here  refer  only  to  certain  problems  that  are  asso- 
ciated with  the  seasons.  Here,  as  under  the  subject  of  the 
earth  as  a  globe,  it  is  too  commonly  the  practice  to  learn  defi- 
nitions, instead  of  developing  a  real  knowledge  of  the  subject 
by  the  study  of  gradually  accumulated  observations.  The  need 
of  plenty  of  time,  only  to  be  secured  by  carrying  on  observa- 
tions during  one  or  two  years,  is  nowhere  better  illustrated  than 
in  this  chapter  of  the  subject.  It  is  impossible  to  compress  the 
necessary  observations  into  the  short  time  during  which  a  high- 
school  course  would  be  concerned  with  the  atmosphere.  Ade- 
quate attention  to  the  subject  can  be  obtained  only  when  the 
work  is  distributed  over  a  long  period  in  the  grammar  school, 
associated  either  with  geography  or  with  nature  study. 

The  Seasons.  The  procession  of  phenomena  observable  in  the 
annual  succession  of  the  seasons  may  be  appreciated  in  early 
school  years.  The  observations  here  described  are  intended  to 
connect  the  simplest  seasonal  phenomena  with  their  causes, 
which  are  to  be  found  in  the  revolution  of  the  earth  around  the 
sun,  and  in  the  resultant  northing  and  southing  of  the  sun  (or 
its  movement  in  declination,  —  declination  in  the  sky  being  the 
equivalent  of  latitude  on  the  earth). 

The  fact  of  seasonal  change  having  been  already  recorded  in 
a  most  elementary  way,  let  a  second  record  be  made  in  connec- 
tion with  a  search  for  the  causes  of  change,  as  follows  :  at  in- 
tervals of  a  fortnight  or  a  month  determine  the  midday  altitude 
of  the  sun.  At  similar  intervals  determine  the  time,  and,  if 
possible,  the  compass  direction,  of  sunrise  and  sunset.  Again, 
at  similar  intervals,  have  the  scholars,  or  at  least  the  brighter 
ones,  note  the  star  groups  that  appear  in  the  east  shortly  after 
the  time,  and  opposite  to  the  point,  of  sunset. 

It  is  manifest  that  this  requires  observations  outside  of  the 
school  session  and  sometimes  at  rather  inconvenient  hours.  But 
I  would  protest  against  the  implication  contained  in  objections 
to  outside  work,  that  lessons  are  so  distasteful  that  none  of  the 
scholars  will  willingly  give  a  little  of  their  free  time  to  such 


230  EDUCATIONAL  ESSAYS 

details  as  are  here  suggested.  Early  summer  sunrise  can  be  timed 
from  sunset  when  it  has  been  discovered  during  the  winter  that 
sunrise  and  sunset  occur  symmetrically  before  and  after  mid- 
day, or  the  moment  when  the  sun -reaches  its  highest  altitude 
(meridian  culmination).  The  general  adoption  of  standard  time 
introduces  some  confusion  here,  for  it  is  desirable  that  sunrise 
and  sunset  should  be  recorded  in  local  solar  time.  A  watch  kept 
to  such  time  by  observations  of  the  sun  at  midday  is  useful  in  this 
connection.  The  watch  will  then  give  the  necessary  correction  for 
the  steeple  clocks  and  factory  whistles,  by  which  some  scholars 
may  have  to  make  their  morning  and  evening  records. 

A  pocket  compass  for  measuring  the  direction  of  sunrise  and 
sunset  may  be  lent  to  those  scholars  whose  homes  give  the  best 
view  of  the  horizon.  Compass  readings  should  be  corrected  for 
local  variation  of  the  needle  to  give  true  bearings.  The  direc- 
tion of  early  sunrise  may  be  determined  from  that  of  late  sun- 
set when  it  has  been  discovered  that  the  two  are  symmetrical 
with  respect  to  the  true  meridian. 

All  the  facts  thus  determined  vary  systematically  and  in  cor- 
relation with  one  another.  The  discovery  of  their  system  of 
change  and  of  the  correlations  in  the  system  should,  if  possible, 
be  reserved  for  the  scholars.  Their  intelligence  is  only  half  de- 
veloped if  the  discoveries  that  they  can  make  are  made  for 
them.  In  such  case  it  may  be  claimed  that  time  is  saved,  and 
that  the  results  reached  are  the  same ;  but  it  should  be  seen, 
on  the  other  hand,  that  the  scholars  lose  much  appreciation  of 
the  result  if  they  do  not  find  it  for  themselves,  and  that  they 
will  fail  entirely  to  acquire  the  power  and  the  habit  of  discover- 
ing if  they  have  no  practice  in  it.  If  American  schools  are 
developed  on  a  truly  democratic  basis,  as  befits  republican 
institutions,  one  of  their  chief  values  will  be  that  they  aid  in 
giving  every  boy  and  girl  in  the  land  a  chance  to  emerge  from 
the  mass,  where  individuality  is  lost,  and  to  reach  a  position  in 
which  they  can  do  the  most  good  for  themselves,  their  homes, 
and  their  country.  The  cultivation  of  intelligence  is  as  essen- 
tial to  this  end  as  the  acquisition  of  knowledge.  The  obser- 
vations and  correlations  now  in  discussion  may  be  made  to 
contribute  usefully  to  both  these  attainments. 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  231 

The  sun's  midday  altitude  should  be  tabulated,  and  the  change 
in  its  value  should  be  indicated  graphically.  Records  thus  kept 
are  in  themselves  educative,  not  only  in  forming  habits  of  ac- 
curacy and  neatness,  but  still  further  in  familiarizing  the  pupils 
with  the  several  methods  of  record,  each  best  for  its  own  purpose. 
Graphic  record  may  be  made  on  a  diagram  in  which  horizontal 
measures  represent  time  (dates)  and  vertical  measures  repre- 
sent angular  altitude  (Fig.  2).  As  the  line  connecting  successive 
points  of  observation  is  seen  to  be  not  straight  but  curved,  let 
expectation  be  aroused  as  to  the  probable  result  of  further  ob- 
servations, thus  developing  the  habit  of  thinking  forward  from 
a  basis  of  observations  in  the  past  and  present.  Test  the  ex- 
pectations by  comparison  with  later  observations,  and  thus 


70- 

60 
50 

40 

30 'J 

20 

10 

0 


,  Sept .  ,  Oct.  ,  Nov.  ,  Dec.  ,  Jan.  ,  Feb,  ,  Mar.  ,  Apr.  (  May  ,  June 


FIG.  2.    DIAGRAM  OF  THE  SUN'S  MIDDAY  ALTITUDE 


develop  the  more  important  habit  of  not  jumping  at  conclusions. 
The  frequency  of  sun  observations  should  be  increased  as  the 
solstices  are  approached,  in  order  to  give. good  determination  of 
those  important  dates.  Few  pupils  will  fail  to  .await  with  inter- 
est the  first  observations  after  the  Christmas  holidays,  or  to 
continue  observations  with  unflagging  interest  even  into  the 
hot  weather  of  late  June.  It  is  conceivable  that  some  children 
might  even  carry  on  observations  of  this  kind  through  the  sum- 
mer vacation  in  order  to  complete  their  curve  for  the  year.  A 
graphic  bisection  of  the  upper  and  lower  culminations  of  the 
curve,  by  lines  drawn  through  the  middle  points  of  horizontal 
chords,  will  give  good  determinations  of  the  dates  of  the  sol- 
stices. When  the  upper  and  lower  limits  of  the  curve  are  well 
determined,  draw  horizontal  lines  tangent  to  them,  and  draw  a 
third  horizontal  line  midway  between  these  tangents.  Lead  up 
to  the  discovery  that  this  middle  line  represents  the  sky  equator, 


232 


EDUCATIONAL  ESSAYS 


| 


Sert. 


Die. 


Jt,n. 


F  b. 


| 

/ 


that  the  date  of  the  equinoxes  is  given  at  the  two  intersections 
of  the  equator  and  the  sun's  path,  and  that  the  angular  distance 
(decimation)  of  the  sun  north  or  south  of  the  equator  can  easily 
be  roughly  determined  for  any  day  of  the  year  by  measuring 
up  or  down  from  the  equator  line  to  the  curved  sun  path.  Then, 
and  not  properly  till  then,  are  young  geographers  ready  to  use 
the  noon  altitude  and  declination  of  the  sun  in  determining  their 
latitude.  When  this  stage  is  reached,  better  values  of  the  sun's 

declination  may  be  taken 
from  the  Nautical  Almanac 
for  the  current  year,  accessi- 
ble in  the  larger  public  libra- 
ries. If  it  is  not  accessible 
there,  ask  the  librarian  to  get 
it.  The  teacher  of  mathe- 
matics should  be  able  to 
explain  how  to  use  it  in  find- 
ing the  sun's  declination  on 
any  date. 

The  Year,  The  time  and 
direction  of  sunrise  and  sun- 
set should  be  tabulated  and 
diagramed.  The  correlation 
of  the  day's  length,  the  di- 
rection of  the  sun  at  rising 
and  setting,  and  the  changes 
in  midday  altitude  are  most 
instructive.  Each  quantity 
affords  occasion  for  predic- 
tion and  verification  of  its  future  values.  All  the  changes  in  these 
quantities  are  run  in  a  period  of  365  days,  and  in  the  same  period 
the  star  group  first  seen  in  the  east  shortly  after  sunset  is  again 
seen  there  at  the  same  hour.  Now  let  the  scholars  try  to  explain 
this  return  to  a  previous  condition,  suggesting  to  them  that  a 
line  may  be  imagined  starting  at  the  sun,  passing  through  the 
earth,  and  extending  to  the  distant  stars.  This  line  has  been  found 
to  sweep  through  the  sky,  pointing  to  one  star  group  after  another, 
and  to  return  to  the  original  group  in  the  same  period  as  that 


JUy 


FIG.  3.   DIAGRAM  OF  SUNRISE  AND 
SUNSET  HOURS 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  233 

in  which  the  noon  altitude  and  its  correlated  quantities  run 
through  their  variations.  Then  the  earth  must  go  around  the 
sun  once  in  365  days.  The  time  unit,  called  a  year,  has  long 
been  familiar  to  the  scholars ;  they  have  probably  heard  or  read 
that  the  earth  goes  around  the  sun  in  a  year,  but  those  words 
are  now  fuller  of  meaning  than  they  were  ever  before.  The 
sensible  constancy  of  the  sun's  apparent  diameter  (determined 
by  letting  a  ray  of  sunlight  pass  through  a  pin  hole  in  one  sheet 
of  paper  and  fall  upon  another  sheet  at  a  fixed  distance  from 
the  pin  hole)  should  serve  to  give  a  good  idea  of  the  form  of 
the  curve  or  orbit  that  the  earth  runs  around. 

In  order  to  give  a  more  satisfactory  determination  of  the 
length  of  the  year  than  can  be  obtained  merely  by  general  in- 
spection of  the  eastern  constellations  after  sunset,  the  following 
plan  may  be  adopted  :  a  series  of  observations  in  September 
and  October  will  show  that  the  stars  occupy  more  and  more 
western  positions  at  a  given  hour  on  successive  evenings.  Let 
the  more  skillful  scholars  make  record  of  the  position  of  some 
recognizable  star  with  respect  to  a  roof  or  chimney  at  a  certain 
hour  on  a  certain  evening,  then  ask  them  to  discover  when  the 
star  will  again  be  in  that  position  at  that  hour.  It  will  be  well 
to  have  records  of  this  sort  made  on  several  different  evenings, 
so  as  to  lessen  the  possible  trouble  from  cloudy  evenings  in  the 
following  year. 

Inclined  Attitude  of  Axis  to  Orbit.  The  facts  regarding  noon 
altitude  and  the  correlated  quantities  can  all  be  explained  if  it 
be  suggested  that  the  axis  on  which  the  earth  has  been  found 
to  turn  does  not  stand  vertical  to  the  plane  of  the  orbit  in 
which  it  has  been  found  to  revolve.  Here  again  a  globe  is  of 
value  as  a  mental  aid  and  an  aid  in  visualizing  the  necessary 
geometrical  relations.  So  are  the  diagrams  that  one  usually 
finds  in  text-books,  although  they  are  much  less  serviceable 
than  globes.  Whether  children  of  under  fourteen  years  of  age 
can  discover  this  solution  of  the  problem  or  not  remains  to  be 
proved.  At  least  they  should  have  a  good  chance  to  show  their 
capacity  to  discover  it,  a  carefully  prepared  chance,  approached 
by  the  slow  accumulation  of  pertinent  observations,  all  familiar- 
ized by  repetition. 


234  EDUCATIONAL  ESSAYS 

A  simple  construction  of  the  earth's  orbit  is  also  serviceable 
at  this  stage.  Draw  upon  a  sheet  of  paper  about  a  foot  square 
a  line  through  its  middle  parallel  to  one  side.  Locate  the  mid- 
dle point  of  the  line.  Construct  a  scale  whose  units  are  ^^  of 
the  side  of  the  paper,  so  that  two  pins,  three  units  apart,  can 
be  driven  into  the  middle  line  symmetrically  on  either  side  of 
the  middle  point.  Lay  a  loop  of  thread  or  fine  string  189  units 
in  perimeter  over  the  pins,  stretch  it  tight  with  a  pencil,  and 
draw  a  curve  thus  guided.  This  nearly  circular  curve  shows  the 
true  pattern  of  the  earth's  orbit,  the  units  of  the  scale  being 
millions  of  miles.  Take  out  one  of  the  pins,  and  around  the  other 
draw  a  little  circle,  a  trifle  less  than  a  unit  in  diameter,  to  repre- 
sent the  sun ;  a  good-sized  pin  head  will  not  be  much  too  small 
for  it.  Assuming  that  the  north  star  is  above  the  plane  of  the 
orbit  (or  paper),  the  earth  moves  around  the  orbit  so  as  to  pass 
from  right  to  left  when  viewed  from  the  sun.  Find  the  point  on 
the  orbit  that  is  nearest  to  the  sun  (it  must  lie  where  the  orbit 
is  cut  by  that  half  of  the  middle  line  which  passes  through  the 
sun).  Conveniently  for  our  memories,  the  sun  celebrates  New 
Year's  Day  by  passing  through  this  "  near  sun  point,"  or  peri- 
helion. July  i  sees  the  earth  at  the  opposite  "  far  sun  point,"  or 
aphelion.  Go  backward  along  the  orbit  from  perihelion  one  ninth 
of  a  quadrant  arc  ;  this  is  the  point  occupied  on  December  21, 
the  date  of  the  sun's  least  midday  altitude,  or  the  winter  sol- 
stice. Draw  a  line  from  this  point  through  the  sun  ;  it  intersects 
the  orbit  at  the  summer  solstice,  which  the  earth  passes  on 
June  21.  Draw  a  line  through  the  sun  at  right  angles  to  the 
solsticial  line;  it  intersects  the  orbit  in  the  equinoctial  points. 
Set  up  a  small  ball  on  a  vertical  axis  to  represent  the  earth  at  the 
winter  solstice ;  the  sun  can  then  be  imagined  to  illuminate  the 
near  half  of  the  earth ;  the  day-and-night  circle  will  separate 
the  illuminated  half  from  the  dark  half  of  the  earth.  As  the 
earth  now  stands,  with  a  vertical  axis,  the  plane  of  the  equator 
passes  through  the  sun,  but  this  has  been  shown  by  observa- 
tion to  be  impossible  at  the  time  of  the  winter  solstice.  On 
that  date  the  sun  is  23°  south  of  the  equator.  The  axis  of  the 
earth  must  therefore  be  tilted  23°  from  the  vertical  and  away 
from  the  sun  in  order  to  imitate  actual  conditions. 


EXERCISES  IN  PHYSICAL  GEOGRAPHY  235 

As  the  prolonged  axis  meets  the  sky  in  the  same  point  at  all 
seasons  of  the  year,  the  attitude  of  the  axis  must  always  be 
parallel  to  its  initial  position.  Carry  the  earth  around  its  orbit, 
holding  the  axis  properly  on  the  way,  and  observe  the  relative 
attitude  of  the  day-and-night  circle  at  different  times  of  year. 
All  the  peculiar  variations  of  the  sun's  midday  altitude,  of  the 
times  and  directions  of  sunrise  and  sunset,  and  of  the  length  of 
day  and  night  can  be  explained  by  this  little  working  model ; 
hence  it  may  be  fairly  said  to  present  the  conditions  of  nature. 
It  is  well  that  the  scholar  should  know  that  it  is  entirely  on  the 
basis  of  such  agreements  between  hypothesis  and  fact  that 
text-books  make  statements  about  the  inclination  of  the  earth's 
axis,  the  duration  of  its  annual  revolution,  and  so  on.  There  is 
no  other  door  by  which  one  can  really  enter  the  domain  of 
knowledge,  where  the  motto  is  written :  "  Truth  for  authority, 
not  authority  for  truth." 


XII 
FIELD  WORK   IN  PHYSICAL  GEOGRAPHY 

The  character  of  the  practical  exercises  in  a  course  in  physical 
geography  that  follows  a  course  on  geology  will  be  very  different 
from  that  in  one  which  precedes  a  course  in  geology,  or  which 
stands  alone.  The  first  of  these  arrangements  is  so  unadvisable 
that  it  need  not  be  considered ;  the  second  is  common  enough 
for  those  students  who  go  to  colleges  after  finishing  a  high-school 
course ;  the  third  is  still  more  common,  and  will  remain  so  for 
years  to  come ;  hence  the  third  alone  will  be  considered  here. 
Furthermore,  as  our  title  refers  only  to  those  practical  exercises 
which  are  involved  in  field  work,  laboratory  exercises  will  not 
here  be  discussed.  The  problem  is  thus  narrowed  down  to  the 
selection  of  outdoor  exercises  in  physical  geography  for  a  class 
of  students  who  have  not  studied,  and  who  may  never  study, 
geology.  It  will  be  still  further  narrowed  by  agreeing  that 
exercises  concerning  the  earth  as  a  globe,  the  atmosphere,  and 
the  ocean  are  not  at  present  in  consideration,  and  hence  that 
exercises  on  the  lands,  where  physical  geography  and  physical 
geology  run  so  close  together,  are  alone  to  be  examined. 

The  first  point  to  bear  in  mind  is  that  the  exercises  should  be 
so  planned  as  to  lead  towards  their  object,  namely,  a  real  under- 
standing of  the  existing  lands  on  which  we  live,  with  particular 
attention  to  those  elements  which  are  of  consequence  as  environ- 
ments, controlling  our  way  of  living.  This  at  once  makes  a  dis- 
tinction between  exercises  for  a  course  on  physical  geography 
and  exercises  for  a  course  on  physical  geology,  even  though  the 
exercises  lead  over  the  same  paths  and  stop  at  the  same  places ; 
for  exercises  in  geology  have  as  their  chief  object  the  interpreta- 
tion of  the  past  history  of  the  earth  through  its  present  condi- 
tion, and  this  object  should  always  be  borne  in  mind  if  geology 
and  not  geography  is  to  be  taught.  It  may  be  noted,  however, 
that  as  the  history  of  the  past  cannot  be  really  understood  until 

236 


FIELD  WORK  IN  PHYSICAL  GEOGRAPHY  237 

the  processes  of  the  present  are  made  familiar,  it  is  eminently 
appropriate  that  physiographic  field  work,  in  which  emphasis  is 
laid  on  present  conditions,  should  precede  geological  field  work, 
which  is  laid  on  the  sequence  of  past  events.  It  was  with  this 
principle  in  mind  that  the  Committee  of  Ten  recommended, 
some  years  ago,  the  postponement  of  geology  to  the  college 
course,  and  the  general  introduction  of  practical  exercises  as 
a  part  of  physical  geography  in  the  high-school  course. 

Another  important  point  is  that  field  exercises  in  the  autumn, 
when  the  text-book  work  is  only  just  opening,  should  relate  to 
general  characteristics  of  the  lands  as  illustrated  by  specific 
facts,  and  that  the  study  of  different  kinds  of  land  forms 
should  be  as  a  rule  postponed  to  spring  excursions,  after  a 
larger  view  of  the  subject  has  been  acquired  through  the  winter 
months.  Let  the  students  then  be  asked  in  September  and 
October  to  look  about  them  to  try  to  discover  what  are  the 
most  general  characteristics  of  the  lands,  and  where  and  how 
they  may  be  best  illustrated  by  local  examples.  At  the  close 
of  field  exercises  running  through  two  fall  months,  it  should 
have  been  observed,  or  reasonably  inferred,  that  the  lands  are 
those  parts  of  the  earth's  rocky  crust  that  rise  above  the  seas, 
and  that  are  thereby  directly  exposed  to  sunshine,  to  at- 
mospheric action,  and  to  stream  work  (thus  being  strongly 
contrasted  with  the  sea  floors) ;  that  in  consequence  of  this 
exposure  the  land  surface  is  under  changing  conditions  of  light 
and  darkness,  of  heat  and  cold,  of  aridity  and  humidity,  of 
movement  and  rest,  of  chemical  and  organic  processes ;  that 
chief  among  the  consequences  of  these  activities  is  the  pro- 
gressive disintegration  of  the  surface  rocks,  thus  forming  rock 
waste  and  soil,  and  the  progressive  down-slope  removal  of  the 
waste  from  higher  to  lower  ground,  and  ultimately  to  the  ocean, 
—  or,  in  brief,  that  the  waste  of  the  land  is  the  gain  of  the  sea ; 
that  the  action  of  rain-,  snow-,  and  spring-fed  streams  is  particu- 
larly important  in  the  transportation  of  waste,  to  such  a  degree 
that  the  pathway  of  the  streams  is  usually  worn  down  below  the 
adjacent  land  surface,  just  as  a  much-used  and  poorly-cared-for 
road  is  worn  down,  but  with  the  notable  differences,  that  while 
the  road  may  go  uphill  and  downhill,  the  pathway  or  channel  of 


238  EDUCATIONAL  ESSAYS 

the  streams  is  always  downhill,  and  that  while  roads  may  run 
crosswise  and  form  a  network,  streams  tend  to  join  each  other 
and  thus  form  a  branchwork. 

While  local  observations  are  accumulating,  it  is  for  the 
teacher  to  emphasize  their  importance  by  telling  something  of 
the  results  of  observation  elsewhere.  Rocks,  weather,  soil, 
wash,  streams,  valleys,  and  hills  are  of  world-wide  distribution. 
They  all  vary  in  many  respects  from  place  to  place  over  the 
lands,  yet  they  all  maintain  their  essential  characteristics.  The 
capacity  to  see  facts  of  these  kinds  can  be  acquired  almost  any- 
where and  utilized  almost  everywhere.  It  is  of  the  utmost  im- 
portance that  this  aspect  of  home  field  study  and  its  relation  to 
the  study  of  the  world  should  be  appreciated.  Just  as  soon  as 
a  group  of  home  facts  is  well  apprehended  and  generalized,  let 
the  teacher  confirm  its  value  by  telling  something  of  the  wide 
distribution  of  such  facts  over  the  world,  instancing  examples 
where  their  value  is  greater  or  less  than,  or  equal  to,  their  value 
in  the  home  field.  Local  field  work  may  be  greatly  enriched  in 
this  way. 

During  the  establishment  of  the  fundamental  generalizations, 
special  attention  may  be  given  to  some  of  the  commoner  min- 
erals and  rocks  in  the  local  field,  and  to  the  manner  in  which 
they  are  disintegrated,  but  the  study  of  mineralogy  as  such 
should  be  set  aside  for  another  occasion.  Familiarity  should  be 
gained  with  the  processes  whereby  the  disintegrating  rock  waste 
creeps  and  washes  downhill  to  the  streams,  constantly  removed 
and  constantly  renewed,  and  whereby  the  streams  comminute 
the  waste  and  transport  it  along  their  valleys  toward  the  sea ; 
attention  should  be  given  to  the  forms  assumed  by  the  waste  of 
the  land  on  its  way  to  the  sea,  and  the  use  made  of  the  slowly 
moving  waste  by  plants  and  animals.  Gradually  the  great  gen- 
eralization may  be  reached  that  if  destructive  processes  of  these 
kinds  should  go  on  forever,  the  lands  would  in  time  be  worn  to 
nearly  featureless  lowlands,  close  to  sea-level,  and  that  this  re- 
sult would  already  have  been  reached  had  the  crust  of  the  earth 
stood  still  from  the  .beginning ;  and  then  follows  the  reasonable 
inference  that  inasmuch  as  the  lands  still  possess  abundant  re- 
lief, the  earth's  crust  cannot  always  have  stood  still :  it  must 


FIELD  WORK  IN  PHYSICAL  GEOGRAPHY  239 

have  changed  position,  perhaps  slowly  rising  and  falling,  now 
here,  now  there ;  and  then  it  dawns  upon  the  inquiring  student 
that  the  lands  possess  their  present  forms  because  they  have 
for  ages  been  the  theater  of  the  opposing  processes  of  deforma- 
tion and  denudation ;  that  every  part  of  the  lands  may  be  sup- 
posed to  owe  its  existing  form  to  the  stage  now  reached  by  the 
process  of  denudation  in  overcoming  the  work  of  deformation, 
and  that  no  better  way  of  describing  a  land  form  can  be  found 
than  to  explain  it  in  terms  of  its  origin.  Thus  the  essential  prin- 
ciple of  the  geographical  cycle  is  reached,  and  a  sound  founda- 
tion is  laid  for  all  further  work.  Truly,  it  still  remains  to 
demonstrate  the  correctness  of  all  these  inferences  and  sup- 
positions, but  real  demonstration  is,  I  fear,  not  to  be  accom- 
plished in  the  time  allowed  for  school  exercises,  and  with 
students  of  the  age  appropriate  to  the  exercises  here  con- 
sidered. Demonstration  may  be  quoted,  if  desired,  in  abun- 
dance, but  the  most  that  can  be  expected  in  the  way  of 
first-hand  work  is  to  show  that  the  conclusions  here  announced 
are  reasonable ;  and  on  this  foundation,  text-book  work  may 
proceed  with  good  effect  through  the  winter. 

It  should  be  clearly  understood  that  work  of  this  kind  is  not 
limited  merely  to  matters  of  observation  and  record.  These  are 
truly  the  first  steps,  but  they  must  be  followed  by  abundant 
thinking ;  indeed,  the  soul  of  the  work  is  gained  only  when  the 
thinking  that  is  inspired  by  the  observations  is  logical,  search- 
ing, critical.  It  is  chiefly  by  this  means  that  a  sound  disciplinary 
value  is  added  to  outdoor  exercises,  and  that  they  become  es- 
sentially scientific,  for  we  here  take  it  to  be  understood  that 
observation  is  by  no  means  the  whole  of  science,  although  it  is 
an  essential  part  thereof.  The  thought  as  well  as  the  facts 
should  be  written  out,  but  inference  and  argument  should  be 
carefully  separated  from  observation  and  generalization.  Thus 
the  work  may  be  macte  as  rigorous  as  is  desired,  and  its  educa- 
tional value  may  be  made  second  to  none ;  but  much  progress 
must  be  made  in  our  schools  before  this  ideal  is  reached. 

Let  it  be  here  noted  that  field  work  of  the  kind  above  suggested 
is  entirely  out  of  reach  of  a  teacher  inexperienced  in  the  field. 
It  is  nothing  more  than  a  travesty  of  observational  exercises 


240  EDUCATIONAL  ESSAYS 

that  is  gained  when  they  are  conducted  by  a  teacher  who  cannot 
"walk  alone"  in  comfort  out  of  doors.  Hence,  when  superin- 
tendents wish  to  introduce  work  of  this  kind,  it  is  incumbent 
upon  them  to  engage  a  teacher  who  is  competent  to  conduct  it. 
The  acceptance  of  an  unprepared  candidate  is  demoralizing  in 
more  ways  than  one  ;  not  only  will  the  educative  and  disciplinary 
elements  of  field  physiography  be  greatly  weakened,  but  those 
conscientious  students  who  are  preparing  themselves  to  teach  real 
physiography  by  devoting  a  good  share  of  time  to  the  study  of 
the  subject  will  be  discouraged  by  seeing  that  ill-prepared  can- 
didates gain  responsible  positions.  This  is  to-day  a  serious  diffi- 
culty, and  it  lies  more  with  superintendents  than  with  any  one 
else  to  correct  it. 

Let  it  be  further  noted  that  every  competent  teacher  should 
be  left  free  to  plan  field  work  with  due  regard  to  local  field  oppor- 
tunity, and  hence  that  field  exercises  must  vary  greatly  in  differ- 
ent schools,  and  that  they  should  not  be  submitted  to  any  uniform 
or  rigid  examination  set  by  a  state  board  of  education.  On  the 
seacoast  field  observations  may  be  directed  to  a  whole  series  of 
problems  that  are  reached  only  through  the  text-book  or  the 
laboratory  at  a  school  in  the  interior  of  the  country.  A  lowland 
district  in  a  dry  climate  suggests  different  exercises  from  a 
mountain  district  in>  a  wet  climate.  The  piedmont  district  of 
the  southern  Appalachians,  with  its  deep  weathered  soils  and  its 
normally  developed  drainage  systems,  could  be  more  simply 
treated  than  the  glaciated  uplands  of  New  England,  where  the 
irregularly  distributed  drift  and  the  many  special  or  abnormal 
drainage  features  will  require  a  very  ingenious  treatment  before 
the  best  advantage  can  be  taken  of  them  in  elementary  work. 
It  would  be  a  mistake  to  impose  a  detailed  outline  of  work  upon 
a  teacher  situated  in  any  one  of  these  districts,  for  real  success 
requires  that  every  competent  teacher  should  plan  local  field 
work  for  himself  ;  hence  the  following  outline  of  a  few  items  for 
autumn  work  in  a  Vermont  high  or  normal  school  should  be  taken 
as  a  suggestion  and  not  as  a  prescription ;  as  a  beginning,  and 
not  as  a  whole  course. 

Autumn.  General  characteristics  of  the  land.  i.  A  weath- 
ering ledge :  decomposition  of  certain  minerals,  action  of 


FIELD  WORK  IN  PHYSICAL  GEOGRAPHY  241 

temperature,  moisture  ;  products  of  disintegration ;  their  rapid 
removal,  chiefly  by  falling  from  steep  rock  faces  which  are 
thus  left  bare  for  continued  active  attack  of  the  weather ;  here 
only  lichens,  etc.,  grow;  the  accumulation  of  fine  waste  on 
little  rocky  shelves  which  are  thus  somewhat  protected  from 
the  weather ;  here  plants  of  higher  order  gain  a  root-hold  ;  yet 
even  here  slow  down-slope  movement  (creeping)  is  caused  by 
washing,  and  by  changes  of  temperature,  etc.  The  prevalent 
coarsely  crystalline  texture  of  the  rocks  and  the  frequent  oc- 
currence of  wrinkled  foliated  structures  may  be  at  once  intro- 
duced as  evidence  that  much  material  has  already  been  removed 
from  this  region  by  erosion ;  for  coarse  crystalline  texture  and 
wrinkled  foliated  structure  cannot  be  produced  by  any  known 
processes  that  operate  at  the  earth's  surface  ;  they  are  explained 
only  by  conditions  that  may  occur  at  depths  of  many  thousands 
of  feet  beneath  the  surface.  Hence  the  visibility  of  such  rock 
structures  suggests  that  the  surface  has  been  worn  down  to 
them  by  the  removal  of  rock  masses  that  once  covered  them, 
probably  to  the  depth  of  thousands  of  feet.  In  time  the  steep- 
faced  ledge  will  be  weathered  back  to  such  a  slope  that  its  waste 
will  form  a  continuous  cover  over  it ;  the  waste  will  be  cloaked 
over  with  plants,  which  delay  but  do  not  prevent  its  removal ; 
the  finer  particles  of  waste  directly  on  the  surface  will  wash  and 
creep  down  the  slope  fastest,  while  new  fragments  are  slowly 
weathered  off  the  ledge  beneath  the  soil  cover.  If  the  processes 
of  removal  are  very  weak,  so  that  less  is  removed  from  the  outer 
surface  than  is  added  by  weathering  the  rocks  beneath  the  under 
surface  of  the  waste  cover,  then  the  cover  increases  in  thickness 
and  thus  decreases  the  effectiveness  of  under-weathering ;  if 
removal  of  waste  at  the  surface  is  active,  the  waste  cover  is 
thinned  and  its  slope  is  decreased,  while  under- weathering  is 
accelerated  ;  thus  in  time  an  essential  balance  comes  to  be  struck 
between  supply  and  loss,  and  the  waste  cover  becomes  a  general 
and  permanent  feature  of  the  surface.  The  flatter  the  surface  is 
worn,  the  slower  the  removal  of  the  waste,  the  finer  its  surface 
particles,  and  the  greater  its  depth.  The  piedmont  district  of  the 
southern  Appalachians  exhibits  abundant  examples  of  this  condi- 
tion of  things ;  their  absence  in  Vermont  must  be  considered  later. 


242  EDUCATIONAL  ESSAYS 

2.  A  small  stream.  Explore  and  map  its  drainage  area  ;  note 
that  its  velocity  is  at  every  point  just  sufficient  to  dispose  of  the 
volume  received  ;  that  it  flows  faster  with  a  slender  current  on 
steeper  slopes,  and  slower  with  a  stouter  current  on  gentler 
slopes ;  that  in  a  cross  section  of  a  straight  channel  the  current 
is  fastest  near  the  middle  and  at  (or  very  close  to)  the  surface ; 
but  in  a  curved  channel  the  line  of  fastest  current  is  displaced 
from  the  middle  of  the  stream  toward  the  outer  side  of  the  curve 
(convex  side  of  stream,  or  concave  bank);  that  the  greater  depth 
of  the  channel  is  usually  nearly  under  the  line  of  fastest  current. 
Note  the  distribution  of  cobbles,  gravel,  sand,  silt,  along  the 
stream  bed.  How  are  these  materials  related  to  the  velocity  of 
the  stream  and  to  the  form  of  the  channel  ?  By  attentively 
watching  the  stream  bed,  particles  of  waste  may  be  seen  dragged 
along  the  bottom  ;  by  studying  the  bed  and  the  banks,  inferences 
may  be  made  as  to  the  progressive  action  of  the  stream  in  the 
past  and  the  future,  and  the  origin  of  its  present  channel  may 
be  discovered.  A  second  visit  should  be  made  just  after  a  rain, 
when  the  stream  is  swollen,  hurried,  and  turbid ;  this  is  the  time 
when  most  of  the  stream's  work  is  done ;  it  has  a  vacation  in 
fair  weather.  The  waste  is  first  received  in  great  part  from  the 
banks,  and  it  is  supplied  to  the  banks  by  washing  and  creeping 
from  the  adjoining  hillsides ;  a  very  small  part  of  its  load  of 
waste  comes  originally  from  its  bed  ;  but  once  in  the  power  of 
the  stream,  the  waste  is  slowly  washed  down  the  channel,  making 
many  stops  on  its  way  to  the  sea,  sometimes  being  laid  down  in 
a  bar,  sometimes  on  the  inner  bank  of  a  curve,  to  be  taken  up 
again  for  a  further  journey  at  some  later  time.  Especially  at 
time  of  flood  is  the  channel  scoured  and  the  waste  carried  for- 
ward ;  as  the  flood  subsides  and  the  current  weakens,  the  coarser 
waste  is  laid  down  first  and  the  finer  waste  later.  Trace  a  stream 
to  its  junction  with  another ;  note  that  the  two  streams  come 
together  at  accordant  grade.  This  is  an  almost  universal  rela- 
tion, and  is  one  of  the  chief  arguments  for  the  erosion  of  valleys 
by  the  streams  that  flow  along  them  (see  passage  from  Playfair, 
cited  in  Russell's  "  Rivers  of  North  America,"  p.  iii).  The  long- 
continued  action  of  streams  must  necessarily  produce  this  rela- 
tion ;  the  occurrence  of  the  relation  proves  the  long-continued 


FIELD  WORK  IN  PHYSICAL  GEOGRAPHY  243 

action  of  the  streams.  But  the  streams  alone  would  cut  vertical- 
walled  trenches.  The  widely  opened  form  of  the  valleys  preva- 
lent in  Vermont,  as  indicated  by  the  moderate  slopes  of  the  valley 
sides,  suggests  that  a  great  amount  of  material  must  have  been 
weathered  and  washed  from  them  down  to  the  streams,  and 
carried  by  the  streams  to  the  rivers  and  the  sea ;  and  thus  some 
confirmation  is  found  for  the  conclusion  already  stated,  based  on 
the  texture  of  the  rocks. 

Most  streams  in  New  England  exhibit  alternations  of  rushing 
rapids  on  rocky  ledges  and  slow-flowing  reaches  in  meadows. 
In  the  reaches,  the  depth  to  which  the  channel  is  cut  is  controlled 
by  the  ledge  at  the  rapids  next  down  the  valley ;  and  the  stream 
is  just  balanced  between  the  average  supply  and  removal  of  the 
waste.  Farther  deepening  of  the  balanced  channel  can  be  allowed 
only  as  the  controlling  ledge  is  slowly  worn  down.  So  delicate 
an  adjustment  of  the  balanced  stream  to  the  ledge  can  only  be 
the  result  of  the  stream's  own  action  on  its  original  valley.  If 
the  original  valley  upstream  from  the  ledge  had  too  gentle  a 
slope,  the  stream  would  have  run  slowly  through  it  (or  the 
stream  might  have  been  much  delayed,  as  in  a  lake  basin  occu- 
pying a  depression  in  the  general  path  of  the  valley)  and  the 
channel  (or  lake  basin)  would  have  been  filled  up  or  aggraded 
with  waste,  thus  producing  the  existing  balanced  slope.  If  the 
channel  were  originally  of  a  stronger  slope,  the  stream  would 
have  run  more  rapidly  and  would  have  worn  down  or  degraded 
its  bed  until  the  present  slope  was  gained.  A  channel  that  has 
a  balanced  slope  may  therefore  be  said  to  be  graded;  the  stream 
may  be  said  to  be  in  a  graded  condition,  or  at  grade ;  and  the  slope 
of  the  balanced  stream  may  be  described  (in  a  slightly  different 
sense  of  the  same  word)  as  having  a  steep  or  a  gentle  grade. 

The  ledge  at  the  rapids  is  slowly  worn  or  degraded  chiefly  by 
the  rasping  of  waste  over  it  at  time  of  flood.  Where  a  stream 
is  actively  deepening  its  channel  in  a  ledge  of  weak  rock  (a  rare 
condition  in  Vermont,  but  common  enough  in  New  York),  the 
channel  is  worn  chiefly  downward,  and  lateral  wearing  is  at  a 
minimum.  Where  a  stream  is  flowing  at  a  grade  through  a 
meadow,  downward  wearing  is  at  a  minimum,  and  lateral  wear- 
ing on  the  outer  bank  is  at  a  maximum  ;  as  a  result  the  meadow 


244  EDUCATIONAL  ESSAYS 

stream  is  constantly  changing  its  channel  by  wearing  away  the* 
outer  bank  and  laying  down  the  wash  thus  gained  on  the  inner 
bank  of  a  curve  farther  forward ;  a  meandering  channel  is  thus 
formed.  Where  the  curves  are  well  pronounced  it  may  be  noted 
that  the  wearing  action  of  the  stream  is  extended  forward  from 
the  concave  (outer)  bank  of  a  meander  so  as  to  include  some- 
thing of  the  up-valley  side  of  the  meadow  lobe  that  enters  the 
next  meander ;  and  that  the  depositing  action  is  extended  for- 
ward from  the  convex  (inner)  bank  of  a  meander  so  as  to  include 
something  of  the  down-valley  side  of  the  meadow  lobe ;  hence 
the  meander  system  is  migrating  downstream  at  the  same  time 
that  it  is  wandering  laterally.  Much  of  the  meadow  or  flood 
plain  may  have  been  worked  over  by  the  shifting  stream,  and 
hence  it  will  be  underlaid  by  stones  and  gravel  such  as  are  to-day 
found  in  the  stream  channel,  however  fine  may  be  the  silt  that 
is  strewn  over  its  surface  at  time  of  overflow. 

The  ledge  that  determines  a  rapid  serves  as  a  local  base-level 
to  the  graded  reach  next  upstream ;  that  is,  its  surface  deter- 
mines a  level  base,  to  which  the  stream  approaches  very  closely, 
but  which  it  cannot  quite  attain.  If  no  ledge  occurs  between 
the  point  of  observation  and  the  sea,  then  the  stream  will  be 
graded  with  respect  to  the  general  base-level  of  the  ocean  surface. 
Most  rivers  are  to-day  graded  with  respect  to  local  or  general 
base-levels  ;  it  is  chiefly  the  smaller  streams  that  are  detained  in 
ungraded  lakes  or  hurried  in  ungraded  torrents.  This  illustrates 
a  general  principle  of  wide  application.  Whenever  the  processes 
that  are  in  operation  upon  a  land  form  tend  to  change  it  to 
another  form,  then  it  cannot  endure  long,  as  the  earth  counts 
time ;  but  when  the  acting  processes  tend  to  maintain  the  form, 
then  it  endures  through  ages.  Lakes  and  rapids  soon  disappear 
by  the  action  of  their  streams  ;  streams  that  possess  such  fea- 
tures are  young,  as  the  earth  views  them.  Graded  reaches  per- 
sist, for  they  are  self-perpetuating;  streams  that  possess  them 
are  mature  or  old.  The  relatively  short  life  of  exposed  ledges 
on  hillsides  and  the  long  endurance  of  waste-covered  or  graded 
slopes  illustrate  the  same  principle. 

Local  illustrations  of  processes  and  principles,  such  as  these 
just  described,  should  be  supplemented  by  citation  of  similar 


FIELD  WORK  IN  PHYSICAL  GEOGRAPHY  245 

illustrations  in  other  parts  of  the  world.  The  teacher  should 
possess  a  mental  fund  of  such  parallel  illustrations,  ready  for 
instant  use.  He  should  also  possess  a  well-selected  series  of 
book  references,  many  of  them  representing  notes  made  in  his 
own  experience  of  reading,  to  which  the  more  assiduous  of  his 
students  may  be  referred  for  fuller  information.  Every  item 
encountered  in  the  local  field  may  thus  be  shown  to  have  its 
fellows  elsewhere  in  the  world,  and  the  value  of  the  local  field  is 
thus  greatly  increased.  In  this  way  every  local  item  comes  to  aid 
the  conception  of  an  ideal  type,  the  generalized  representative 
of  a  class  which  includes  many  distant  examples  as  well  as  the 
local  example  through  which  its  acquaintance  was  first  made. 
Field  work  thus  becomes  naturally  associated  with  book  work. 
As  before  noted,  field  work  remains  far  below  what  it  should  be 
if  it  is  limited  merely  to  the  observation  of  the  examples  that  it 
immediately  presents. 

3.  Drift.  The  hills  and  valleys  of  Vermont,  and  of  New  Eng- 
land in  general,  possess  abundant  deposits  of  unconsolidated 
rock  waste  known  as  drift.  Note  the  varied  composition  of  these 
deposits ;  they  frequently  contain  rock  fragments  unlike  the 
rock  in  the  neighboring  ledges.  The  rock  fragments  are  fre- 
quently firm  and  unweathered  ;  they  are  sometimes,  especially 
in  valleys,  rounded  as  if  waterworn ;  sometimes,  especially  on 
uplands,  roughly  faceted  and  striated,  as  if  dragged  under  heavy 
pressure.  The  structure  and  form  of  these  deposits  is  very 
varied.  Those  containing  faceted  and  striated  stones  or  bowlders 
are  compact  and  unstratified,  often  wrapped  over  the  rock  hills 
as  if  packed  upon  them ;  sometimes  reaching  greater  thickness 
and  rising  in  oval  hills  of  arched  profile,  independent  of  the  rock 
beneath.  Those  containing  rounded  cobbles  and  pebbles,  with 
sand,  are  stratified ;  they  sometimes  form  small  knolls  or  ser- 
pentine ridges  ;  sometimes  plains  or  terraces.  The  rock  beneath 
the  drift  is  usually  firm  and  unweathered ;  its  surface  is  often 
rounded  and  striated,  as  if  it  had  been  scoured  under  heavy 
pressure.  Evidently  the  normal  processes  of  weathering  have 
not  been  active  here,  as  they  have  been  in  the  southern  Appala- 
chians. In  place  of  the  regular  and  well-graded  slopes  of  gen- 
tle curvature,  cloaked  with  abundant  waste  derived  from  the 


246  EDUCATIONAL  ESSAYS 

underlying  rock  and  always  leading  down  to  an  elaborate  branch 
work  of  well-established  watercourses,  such  as  must  characterize 
regions  where  normal  weathering  has  long  been  in  progress,  the 
hills  and  valleys  of  Vermont  present  irregular  forms  ;  ledges  are 
exposed  here  and  there  in  disorder,  irregularly  distributed  drift 
deposits  of  varied  thickness,  structure,  and  form  lie  on  a  firm 
and  smoothed  foundation  of  unweathered  or  little-weathered 
rock ;  the  hillsides  descend  unevenly  to  water  courses  that  ex- 
hibit in  their  ponds  and  rapids  the  most  evident  signs  of  an  early 
stage  of  development.  All  these  abnormal  features  are  to  be 
attributed  to  glacial  action,  whose  geographical  consequences 
in  the  northern  states  are  so  numerous  and  so  important  that 
every  student  of  physiography  should  gain  an  early  acquaint- 
ance with  them. 

As  under  weathering  and  streams,  it  is  by  no  means  advisable 
that  every  student  should  be  expected  to  observe  all  the  items 
here  noted,  or  to  formulate  or  invent  for  himself  all  the  generali- 
zations and  explanations  here  quoted.  The  school  year  is  too 
short  for  that.  But  there  should  be  some  observation,  generali- 
zation, invention,  and  discussion  on  the  part  of  every  student, 
and  in  supplement  to  this  the  teacher  should  add  enough  to 
carry  the  class  through  a  carefully  prepared  course  in  the  ap- 
pointed time.  In  particular  is  it  necessary  that  the  various 
classes  of  facts  that  lead  to  the  most  important  generalizations 
and  that  call  for  the  most  frequent  fundamental  explanations 
should  be  illustrated  by  some  well-selected  examples,  and  that 
these  examples  should  become  familiar  to  the  students  by  direct 
observation.  The  students  should  thus  be  led  directly  to  dis- 
cover or  to  recognize  the  chief  principles  and  general  ideas  of 
land  physiography  —  gradation,  base-leveling,  etc.  —  while  in  the 
presence  of  the  facts  to  which  these  principles  apply.  Only  in 
this  way  can  abstract  principles  gain  real  and  serviceable  appli- 
cation. If  it  occur  to  any  readers  of  these  pages  that  the  topics 
here  suggested  for  field  observation  and  study  possess  some 
measure  of  difficulty,  more  perhaps  than  is  usually  associated 
with  work  on  geographical  excursions,  let  them  be  assured  that 
the  results  are  worth  the  effort  they  may  demand,  and  that  only 
as  physiography  gains  a  seriousness  of  work  comparable  to  that 


FIELD  WORK  IN  PHYSICAL  GEOGRAPHY  247 

in  classics  and  mathematics  will  it  acquire  the  educational  posi- 
tion that  it  deserves. 

Spring.  If  it  be  true  that  field  work  for  the  autumn  months 
must  be  planned  for  each  school  district,  it  is  still  more  true  for 
the  spring  months ;  for  attention  should  then  be  given  to  those 
topics  of  the  text-books  which  find  local  illustration  near  the 
school ;  not  merely  general  topics,  such  as  the  gradation  of  river 
courses,  but  particular  topics,  such  as  the  development  of  flood 
plains,  the  migration  of  divides,  and  the  evolution  of  certain  land 
forms.  Any  little  stream  that  possesses  a  flood  plain  between 
the  inclosing  side  slopes  of  its  valley  serves  to  review  and  to 
justify  everything  that  has  been  learned  about  flood  plains ;  the 
stage  attained  in  the  development  of  the  actual  flood  plain  should 
be  determined  with  respect  to  the  ideal  scheme  of  flood-plain 
development.  Every  divide  from  which  the  two  slopes  are  un- 
symmetrical  is  presumably  a  migrating  divide.  What  changes 
will  probably  be  brought  about  in  stream  courses  and  waste 
slopes  if  the  migration  continue  ?  What  examples  from  other 
parts  of  the  world  may  be  illustrated  by  the  observed  example  ? 
As  to  land  forms,  Vermont  has  an  abundance  of  subdued  moun- 
tains and  of  drift  deposits ;  Kentucky  illustrates  the  dissection 
of  plains  and  plateaus  in  various  stages  ;  central  Pennsylvania 
exhibits  a  beautiful  variety  of  mountain  ridges,  with  an  extraor- 
dinarily well-adjusted  drainage  system ;  the  Carolinas  possess 
a  beautiful  variety  of  coastal  features  ;  Mississippi  and  Louisiana 
share  the  great  flood  plain  of  the  "father  of  waters."  Surely 
there  is  no  lack  of  field  material !  Let  us  hear  from  the  teachers 
who  are  making  a  success  of  their  field  work  as  to  the  examples 
of  land  forms  that  they  are  actually  studying  outdoors. 

In  closing,  let  me  add  a  few  more  pieces  of  advice.  While 
the  field  work  in  the  fall  leads  up  from  various  particular  obser- 
vations to  several  broad  generalizations,  the  spring  work  should 
lead  down  from  a  broad  scheme  of  classification  to  various  par- 
ticular examples  that  come  under  the  scheme.  Every  observed 
fact  should  be  associated  with  the  class  to  which  it  belongs.  As  a 
member  of  this  class,  it  should  be  compared  with  other  members 
known  through  the  text-book,  or  through  outside  reading,  and 
representing  earlier  and  later  stages  of  development.  Particular 


248  EDUCATIONAL  ESSAYS 

effort  should  be  given  to  making  this  part  of  the  work  serious, 
definite,  and  accurate,  for  only  in  this  way  can  a  high  discipli- 
nary value  be  gained  for  field  exercises ;  otherwise  they  are  apt 
to  be  vague,  trifling,  and  uneducative.  Let  attention  be  fre- 
quently turned  at  all  stages  of  the  work  to  the  controls  exerted 
by  physiographic  factors  upon  organic  life,  both  high  and  low ; 
not  because  physical  geography  includes  biology,  but  because  it 
is  desirable  to  form  the  habit  of  recognizing  the  close  correlation 
that  surely  exists  between  inorganic  and  organic  nature.  Con- 
trols illustrated  in  the  field  may  be  verified  by  examples  from 
other  sources,  but  care  should  be  taken  to  avoid  petty  examples 
on  the  one  hand  and  doubtful  examples  on  the  other. 

Finally,  let  it  be  remembered  that  this  is  not  an  outline  of  a 
course  in  geography,  but  some  suggestions  for  one  part  (fall  and 
spring  field  work)  of  a  year's  course  on  one  division  (physical 
geography)  of  geography.  Other  parts  and  other  divisions 
deserve  equally  careful  and  serious  attention. 


UNIVERSITY  OF  CALIFORNIA 

DEPARTMENT  GEOGRAPHY 
PART   TWO 

PHYSIOGRAPHIC  ESSAYS 

XIII 
THE  GEOGRAPHICAL  CYCLE 

The  Genetic  Classification  of  Land  Forms,  All  the  varied  forms 
of  the  lands  are  dependent  upon — or,  as  the  mathematician  would 
say,  are  functions  of  —  three  variable  quantities,  which  may  be 
called  structure,  process,  and  time^  In  the  beginning,  when  the 
forces  of  deformation  and  uplift  determine  the  structure  and  atti- 
tude of  a  region,  the  form  of  its  surface  is  in  sympathy  with  its 
internal  arrangement,  and  its  height  depends  on  the  amount  of 
uplift  that  it  has  suffered.  If  its  rocks  were  unchangeable  under  , 
the  attack  of  external  processes,  its  surface  would  remain  unal- 
tered until  the  forces  of  deformation  and  uplift  acted  again  ;  and 
in  this  case  structure  would  be  alone  in  control  of  form.  But  no  , 
rocks  are  unchangeable  ;  even  the  most  resistant  yield  under  the 
attack  of  the  atmosphere,  and  their  waste  creeps  and  washes 
downhill  as  long  as  any  hills  remain  ;  hence  all  forms,  however 
high  and  however  resistant,  must  be  laid  low,  and  thus  destruc- 
tive process  gains  rank  equal  to  that  of  structure  in  determining 
the  shape  of  a  land  mass.  Process  cannot,  however,  complete 
its  work  instantly,  and  the  amount  of  change  from  initial  form 
is  therefore  a  function  of  time.  Time  thus  completes  the  trio  of 
geographical  controls,  and  is,  of  the  three,  the  one  of  the  most  ( 
frequent  application  and  of  a  most  practical  value  in  geograph- 
ical description. 

Structure  is  the  foundation  of  all  geographical  classifications 
in  which  the  trio  of  controls  is  recognized.   The  Allegheny  pla-  N 
teau  is  a  unit,  a  "  region,"  because  all  through  its  great  extent 
it  is  composed  of  widespread  horizontal  rock  layers.    The  Swiss 

249 


250  PHYSIOGRAPHIC  ESSAYS 

Jura  and  the  Pennsylvania  Appalachians  are  units,  for  they  con- 
sist of  corrugated  strata.  The  Laurentian  highlands  of  Canada 
are  essentially  a  unit,  for  they  consist  of  greatly  disturbed  crys- 
talline rocks.  These  geographical  units  have,  however,  no  such 
simplicity  as  mathematical  units  ;  each  one  has  a  certain  variety. 
The  strata  of  plateaus  are  not  strictly  horizontal,  for  they  slant 
or  roll  gently,  now  this  way,  now  that.  The  corrugations  of  the 
Jura  or  of  the  Appalachians  are  not  all  alike  ;  they  might,  indeed, 
be  more  truly  described  as  all  different,  yet  they  preserve  their 
essential  features  with  much  constancy.  The  disordered  rocks 
of  the  Laurentian  highlands  have  so  excessively  complicated  a 
structure  as  at  present  to  defy  description,  unless  item  by  item  ; 
yet,  in  spite  of  the  free  variations  from  a  single  structural  pat- 
tern, it  is  legitimate  and  useful  to  look  in  a  broad  way  at  such 
a  region,  and  to  regard  it  as  a  structural  unit.  The  forces  by 
which  structures  and  attitudes  have  been  determined  do  not 
come  within  the  scope  of  geographical  inquiry,  but  the  struc- 
tures acquired  by  the  action  of  these  forces  serve  as  the  essen- 
tial basis  for  the  genetic  classification  of  geographical  forms. 
For  the  purpose  of  this  article,  it  will  suffice  to  recognize  two 
great  structural  groups  :  first,  the  group  of  horizontal  structures, 
including  plains,  plateaus,  and  their  derivatives,  for  which  no 
single  name  has  been  suggested  ;  second,  the  group  of  disor- 
dered structures,  including  mountains  and  their  derivatives,  like- 
wise without  a  single  name.  The  second  group  may  be  more 
elaborately  subdivided  than  the  first. 

The  destructive  processes  are  of  great  variety,  —  the  chemical 
action  of  air  and  water,  and  the  mechanical  action  of  wind,  heat, 
and  cold,  of  rain  and  snow,  rivers  and  glaciers,  waves  and  cur- 
rents. But  as  most  of  the  land  surface  of  the  earth  is  acted  on 
chiefly  by  weather  changes  and  running  water,  these  will  be 
treated  as  forming  a  normal  group  of  destructive  processes,  while 
the  wind  of  arid  deserts  and  the  ice  of  frigid  deserts  will  be  con-  j 
sidered  as  climatic  modifications  of  the  norm,  and  set  apart  for 
particular  discussion  ;  a  special  chapter  will  be  needed  to  explain 
the  action  of  waves  and  currents  on  the  shore -lines  at  the  edge 
of  the  lands.  The  various  processes  by  which  destructive  work 
is  done  are  in  their  turn  geographical  features,  and  many  of  them 


THE  GEOGRAPHICAL  CYCLE  251 

are  well  recognized  as  such ;  for  example,  rivers,  falls,  and 
glaciers  ;  but  they  are  too  commonly  considered  by  geographers 
apart  from  the  work  that  they  do,  this  phase  of  the"ir  study 
being,  for  some  unsatisfactory  reason,  given  over  to  physical 
geology.  There  should  be  no  such  separation  of  agency  and  work 
in  physical  geography,  although  it  is  profitable  to  give  separate 
consideration  to  the  active  agent  and  to  the  inert  mass  on  which 
it  works. 

Time  as  an  Element  in  Geographical  Terminology,  The 
amount  of  change  caused  by  destructive  processes  increases 
with  the  passage  of  time,  but  neither  the  amount  nor  the  rate 
of  change  is  a  simple  function  of  time.  The  amount  of  change 
is  limited,  in  the  first  place,  by  the  altitude  of  a  region  above 
the  sea ;  for,  however  long  the  time,  the  normal  destructive 
forces  cannot  wear  a  land  surface  below  this  ultimate  base- 
level  of  their  action,  and  glacial  and  marine  forces  cannot 
wear  down  a  land  mass  indefinitely  beneath  sea-level.  The 
rate  of  change  under  normal  processes,  which  alone  will  be 
considered  for  the  present,  is  at  the  very  first  relatively  moder- 
ate ;  it  then  advances  rather  rapidly  to  a  maximum,  and  next 
slowly  decreases  to  an  indefinitely  postponed  minimum. 

Evidently  a  longer  period  must  be  required  for  the  complete 
denudation  of  a  resistant  than  for  that  of  a  weak  land  mass,  but 
no  measure  in  terms  of  years  or  centuries  can  now  be  given  to 
the  period  needed  for  the  effective  wearing  down  of  highlands 
to  featureless  lowlands.  All  historic  time  is  hardly  more  than  a 
negligible  fraction  of  so  vast  a  duration.  The  best  that  can  be 
done  at  present  is  to  give  a  convenient  name  to  this  unmeasured 
part  of  eternity,  and  for  this  purpose  nothing  seems  more  ap- 
propriate than  a  geographical  cycle.  When  it  is  possible  to  estab- 
lish a  ratio  between  geographical  and  geological  units,  there  will 
probably  be  found  an  approach  to  equality  between  the  duration 
of  an  average  cycle  and  that  of  Cretaceous  or  Tertiary  time,  as 
has  been  indicated  by  the  studies  of  several  geomorphologists. 

"  Theoretical"  Geography.  It  is  evident  that  a  scheme  of  geo- 
graphical classification  that  is  founded  on  structure,  process,  and 
time  must  be  deductive  in  a  high  degree.  This  is  intentionally 
and  avowedly  the  case  in  the  present  instance.  As  a  consequence, 


252  PHYSIOGRAPHIC  ESSAYS 

the  scheme  gains  a  very  "  theoretical  "  flavor  that  is  not  relished 
by  some  geographers,  whose  work  implies  that  geography,  un- 
like all  other  sciences,  should  be  developed  by  the  use  of  certain 
of  the  mental  faculties  only,  —  chiefly  observation,  description, 
and  generalization.  But  nothing  seems  to  me  clearer  than  that 
geography  has  already  suffered  too  long  from  the  disuse  of 
imagination,  invention,  deduction,  and  the  various  other  mental 
faculties  that  contribute  towards  the  attainment  of  a  well-tested 
explanation.  It  is  like  walking  on  one  foot,  or  looking  with  one 
eye,  to  exclude  from  geography  the  "  theoretical "  half  of  the 
brain  power,  upon  which  other  sciences  call  as  well  as  upon  the 
"  practical "  half.  Indeed,  it  is  only  as  a  result  of  misunder- 
standing that  an  antipathy  is  implied  between  theory  and  prac- 
tice ;  for  in  geography,  as  in  all  sound  scientific  work,  the  two 
advance  most  amiably  and  effectively  together.  Surely  the  full- 
est development  of  geography  will  not  be  reached  until  all  the 
mental  faculties  that  are  in  any  way  pertinent  to  its  cultivation 
are  well  trained  and  exercised  in  geographical  investigation. 

All  this  may  be  stated  in  another  way.  One  of  the  most 
effective  aids  to  the  appreciation  of  a  subject  is  a  correct  ex- 
planation of  the  facts  that  it  presents.  Understanding  thus 
comes  to  aid  the  memory.  But  a  genetic  classification  of  geo- 
graphical forms  is,  in  effect,  an  explanation  of  them ;  hence 
such  a  classification  must  be  helpful  to  the  traveling,  studying, 
or  teaching  geographer,  provided  only  that  it  is  a  true  and  nat- 
ural classification.  True  and  natural  a  genetic  classification 
may  certainly  be,  for  the  time  is  past  when  even  geographers 
can  look  on  the  forms  of  lands  as  "  ready-made."  Indeed,  geo- 
graphical definitions  and  descriptions  are  untrue  and  unnatural 
just  so  far  as  they  give  the  impression  that  the  forms  of  the 
lands  are  of  unknown  origin,  not  susceptible  of  rational  ex- 
planation. From  the  very  beginning  of  geography  in  the  lower 
schools  the  pupils  should  be  possessed  with  the  belief  that  geo- 
graphical forms  have  meaning,  and  that  the  meaning  or  origin 
of  so  many  forms  is  already  so  well  assured  that  there  is  every 
reason  to  think  that  the  meaning  of  all  the  others  will  be  dis- 
covered in  due  time.  The  explorer  of  the  earth  should  be  as 
fully  convinced  of  this  principle,  and  as  well  prepared  to  apply 


THE  GEOGRAPHICAL  CYCLE  253 

it,  as  the  explorer  of  the  sky  is  to  carry  physical  principles  to 
the  farthest  reach  of  his  telescope,  his  spectroscope,  and  his 
camera.  The  preparation  of  route  maps  and  the  determination 
of  latitude,  longitude,  and  altitude  for  the  more  important  points 
is  only  the  beginning  of  exploration,  which  has  no  end  till  all 
the  facts  of  observation  are  carried  forward  to  explanation. 

It  is  important,  however,  to  insist  that  the  geographer  needs  to 
know  the  meaning,  the  explanation,  and  the  origin  of  the  forms 
that  he  looks  at,  simply  because  of  the  aid  thus  received  when 
he  attempts  to  observe  and  describe  the  forms  carefully.  It  is 
necessary  clearly  to  recognize  this  principle,  and  constantly  to 
bear  it  in  mind,  if  we  would  avoid  the  error  of  confounding  the 
objects  of  geographical  and  geological  study.  The  latter  ex- 
amines the  changes  of  the  past  for  their  own  sake,  inasmuch  as 
geology  is  concerned  with  the  history  of  the  earth ;  the  former 
examines  the  changes  of  the  past  only  so  far  as  they  serve  to 
illuminate  the  present,  for  geography  is  concerned  essentially 
with  the  earth  as  it  now  exists.  Structure  is  a  pertinent  ele- 
ment of  geographical  study  when,  as  nearly  always,  it  influences 
form  ;  no  one  would  to-day  attempt  to  describe  the  Weald  with- 
out some  reference  to  the  resistant  chalk  layers  that  determine 
its  rimming  hills.  Process  is  equally  pertinent  to  our  subject, 
for  it  has  everywhere  been  influential  in  determining  form  to  a 
greater  or  less  degree,  and  it  is  everywhere  in  operation  to-day. 
It  is  truly  curious  to  find  geographical  text-books  which  accept 
the  movement  of  winds,  currents,  and  rivers  as  part  of  their  re- 
sponsibility, and  yet  which  leave  the  weathering  of  the  lands 
and  the  movement  of  land  waste  entirely  out  of  consideration. 
Time  is  certainly  an  important  geographical  element,  for  where 
the  forces  of  uplift  or  deformation  have  lately  (as  the  earth 
views  time)  initiated  a  cycle  of  change,  the  destructive  proc- 
esses can  have  accomplished  but  little  work,  and  the  land 
form  is  "young";  where  more  time  has  elapsed,  the  surface 
will  have  been  more  thoroughly  carved,  and  the  form  thus 
becomes  "  mature  "  ;  and  where  so  much  time  has  passed  that 
the  originally  uplifted  surface  is  worn  down  to  a  lowland  of 
small  relief,  standing  but  little  above  sea-level,  the  form  de- 
serves to  be  called  "  old."  A  whole  series  of  forms  must  be  in 


254  PHYSIOGRAPHIC  ESSAYS 

this  way  evolved  in  the  life  history  of  a  single  region,  and  all 
the  forms  of  such  a  series,  however  unlike  they  may  seem  at 
first  sight,  should  be  associated  under  the  element  of  time,  as 
merely  expressing  the  different  stages  of  development  of  a 
single  structure.  The  larva,  the  pupa,  and  the  imago  of  an 
insect,  or  the  acorn,  the  full-grown  oak,  and  the  fallen  old 
trunk,  are  no  more  naturally  associated  as  representing  the  dif- 
ferent phases  in  the  life  history  of  a  single  organic  species  than 
are  the  young  mountain  block,  the  maturely  carved  mountain 
peaks  and  valleys,  and  the  old  mountain  peneplain,  as  represent- 
ing the  different  stages  in  the  life  history  of  a  single  geographical 
group.  Like  land  forms,  the  agencies  that  work  upon  them 
change  their  behavior  and  their  appearance  with  the  passage  of 
time.  A  young  land  form  has  young  streams  of  torrential  activ- 
ity, while  an  old  form  would  have  old  streams  of  deliberate,  or 
even  of  feeble,  current,  as  will  be  more  fully  set  forth  below. 

The  Ideal  Geographical  Cycle.  The  sequence  in  the  develop- 
mental changes  of  land  forms  is,  in  its  own  way,  as  systematic 
as  the  sequence  of  changes  found  in  the  more  evident  develop- 
ment of  organic  forms.  Indeed,  it  is  chiefly  for  this  reason  that 
the  study  of  the  origin  of  land  forms  —  or  geomorphogeny,  as 
some  call  it  —  becomes  a  practical  aid,  helpful  to  the  geographer 
at  every  turn.  This  will  be  made  clearer  by  the  specific  con- 
sideration of  an  ideal  case,  and  here  a  graphic  form  of  expression 
will  be  found  of  assistance. 

In  Fig.  4  the  base  line  «o>  represents  the  passage  of  time, 
while  verticals  above  the  base  line  measure  altitude  above  sea- 
level.  At  the  epoch  I  let  a  region  of  whatever  structure  and 
form  be  uplifted,  B  representing  the  average  altitude  of  its 
higher  parts  and  A  that  of  its  lower  parts,  AB  thus  measuring 
its  average  initial  relief.  The  surface  rocks  are  attacked  by  the 
weather.  Rain  falls  on  the  weathered  surface  and  washes  some 
of  the  loosened  waste  down  the  initial  slopes  to  the  trough  lines, 
I  where  two  converging  slopes  meet ;  there  the  streams  are  formed, 
flowing  in  directions  consequent  upon  the  descent  of  the  trough 
lines.  The  machinery  of  the  destructive  processes  is  thus  put 
in  motion,  and  the  destructive  development  of  the  region  is  be- 
gun. The  larger  rivers,  whose  channels  initially  had  an  altitude 


THE  GEOGRAPHICAL  CYCLE  255 

A,  quickly  deepen  their  valleys,  and  at  the  epoch  2  have  reduced 
their  main  channels  to  a  moderate  altitude  represented  by  C. 
The  higher  parts  of  the  interstream  uplands,  acted  on  only  by 
the  weather  without  the  concentration  of  water  in  streams,  waste 
away  much  more  slowly,  and  at  epoch  2  are  reduced  in  height 
only  to  D.  The  relief  of  the  surface  has  thus  been  increased 
from  AB  to  CD.  The  main  rivers  then  deepen  their  channels 
very  slowly  for  the  rest  of  their  lives,  as  shown  by  the  curve  CEGJ, 
and  the  wasting  of  the  uplands,  much  dissected  by  branch  streams, 
comes  to  be  more  rapid  than  the  deepening  of  the  main  valleys, 
as  shown  by  comparing  the  curves  DFHK  and  CEGJ.  The 
period  3-4  is  the  time  of  the  most  rapid  consumption  of  the\ 
uplands,  and  thus  stands  in  strong  contrast  with  the  period  I-2J 
when  there  was  the  most  rapid  deepening  of  the  main  valleys.. 
In  the  earlier  period  the  relief  was  rapidly  increasing  in  value, 


FIG.  4 

as  steep-sided  valleys  were  cut  beneath  the  initial  troughs. 
Through  the  period  2-3  the  maximum  value  of  relief  is  reached, 
and  the  variety  of  form  is  greatly  increased  by  the  head  ward 
growth  of  side  valleys.  During  the  period  3-4  relief  is  decreas- 
ing faster  than  at  any  other  time,  and  the  slope  of  the  valley  sides 
is  becoming  much  gentler  than  before ;  but  these  changes  ad- 
vance much  more  slowly  than  those  of  the  first  period.  From 
epoch  4  onward  the  remaining  relief  is  gradually  reduced  to 
smaller  and  smaller  measures,  and  the  slopes  become  fainter 
and  fainter,  so  that  some  time  after  the  latest  stage  of  the  dia- 
gram the  region  is  only  a  rolling  lowland,  whatever  may  have 
been  its  original  height.  So  slowly  do  the  later  changes  advance 
that  the  reducfion  of  the  reduced  JK  to  half  of  its  value  might 
well  require  as  much  time  as  all  that  which  has  already 
elapsed  ;  and  from  the  gentle  slopes  that  would  then  remain, 
the  further  removal  of  waste  must  indeed  be  exceedingly  slow. 


256  PHYSIOGRAPHIC  ESSAYS 

The  frequency  of  torrential  floods  and  of  landslides  in  young 
and  in  mature  mountains,  in  contrast  to  the  quiescence  of  the 
sluggish  streams  and  the  slow  movement  of  the  soil  on  lowlands 
of  denudation,  suffices  to  show  that  rate  of  denudation  is  a 
matter  of  strictly  geographical  as  well  as  of  geological  interest. 

It  follows  from  this  brief  analysis  that  a  geographical  cycle 
may  be  subdivided  into  parts  of  unequal  duration,  each  one  of 
which  will  be  characterized  by  the  degree  and  variety  of  the 
relief,  and  by  the  rate  of  change,  as  well  as  by  the  amount  of 
change  that  has  been  accomplished  since  the  initiation  of  the 
cycle.  There  will  be  a  brief  youth  of  rapidly  increasing  relief, 
a  maturity  of  strongest  relief -and  greatest  variety  of  form,  a 
transition  period  of  most  rapidly  yet  slowly  decreasing  relief, 
and  an  indefinitely  long  old  age  'of  faint  relief,  in  which  further 
changes  are  exceedingly  slow.  There  are,  of  course,  no  breaks 
between  these  subdivisions  or  stages ;  each  one  merges  into  its 
successor,  yet  each  one  is  in  the  main  distinctly  characterized 
by  features  found  at  no  other  time. 

The  Development  of  Consequent  Streams.  The  preceding  sec- 
tion gives  only  the  barest  outline  of  the  systematic  sequence  of 
changes  that  run  their  course  through  a  geographical  cycle.  The 
outline  must  be  at  once  gone  over,  in  order  to  fill  in  the  more 
important  details.  In  the  first  place,  it  should  not  be  implied, 
as  was  done  in  Fig.  4,  that  the  forces  of  uplift  and  deformation 
act  so  rapidly  that  no  destructive  changes  occur  during  their 
operation.  A  more  probable  relation  at  the  opening  of  a  cycle 
of  change  places  the  beginning  of  uplift  at  O  (Fig.  4)  and  its 
end  at  I .  The  divergence  of  the  curves  OB  and  OA  then  implies 
that  certain  parts  of  the  disturbed  region  were  uplifted  more 
than  others,  and  that  from  a  surface  of  no  relief  at  sea-level  at 
epoch  <9,  an  upland  having  AB  relief  would  be  produced  at 
epoch  i.  But  even  during  uplift  the  streams  that  gather  in  the 
troughs  as  soon  as  they  are  defined  do  some  work,  and  hence 
young  valleys  are  already  incised  in  the  trough  bottoms  when 
epoch  i  is  reached,  as  shown  by  the  curve  OA.  The  uplands 
also  waste  more  or  less  during  the  period  of  disturbance,  and 
hence  no  absolutely  unchanged  initial  surface  should  be  found, 
even  for  some  time  anterior  to  epoch  i.  Instead  of  looking  for 


THE  GEOGRAPHICAL  CYCLE  257 

initial  divides,  separating  initial  slopes  which  descend  to  initial 
troughs,  followed  by  initial  streams,  such  as  were  implied  in 
Fig.  4  at  the  epoch  of  instantaneous  uplift,  we  must  always  ex- 
pect to  find  some  greater  or  less  advance  in  the  sequence  of 
developmental  changes,  even  in  the  youngest  known  land  forms. 
"  Initial "  is  therefore  a  term  adapted  to  ideal  rather  than  to 
actual  cases,  in  treating  which  the  term  "sequential"  and  its 
derivatives  will  be  found  more  appropriate.  All  the  changes^ 
which  directly  follow  the  guidance  of  the  ideal  initial  forms  may 
be  called  consequent ;  thus  a  young  form  would  possess  conse- 
quent divides,  separating  consequent  slopes,  which  descend  to 
consequent  valleys,  the  initial  troughs  being  changed  to  conse- 
quent valleys  in  so  far  as  their  form  is  modified  by  the  action 
of  the  consequent  drainage. 

The  Grade  of  Valley  Floors.  The  larger  rivers  soon  —  in  terms 
of  the  cycle  —  deepen  their  main  valleys,  so  that  their  channels 
are  but  little  above  the  base-level  of  the  region ;  but  the  valley 
floor  cannot  be  reduced  to  the  absolute  base-level,  because  the 
river  must  slope  down  to  its  mouth  at  the  seashore.  The  altitude 
of  any  point  on  a  well-matured  valley  floor  must  therefore  de- 
pend on  river  slope  and  distance  from  mouth.  Distance  from 
mouth  may  here  be  treated  as  a  constant,  although  a  fuller  state- 
ment would  consider  its  increase  in  consequence  of  delta  growth. 
River  slope  cannot  be  less,  as  engineers  know  very  well,  than  a 
certain  minimum  that  is  determined  by  volume  and  by  quantity 
and  , texture  of  detritus  or  load.  Volume  may  be  temporarily 
taken  as  a  constant,  although  it  may  easily  be  shown  to  suffer 
important  changes  during  the  progress  of  a  normal  cycle.  Load 
is  small  at  the  beginning  and  rapidly  increases  in  quantity  and 
coarseness  during  youth,  when  the  region  is  intrenched  by  steep- 
sided  valleys  ;  it  continues  to  increase  in  quantity,  but  probably 
not  in  coarseness,  during  early  maturity,  when  ramifying  valleys 
are  growing  by  headward  erosion  and  are  thus  increasing  the 
area  of  wasting  slopes  ;  but  after  full  maturity,  load  continually 
decreases  in  quantity  and  in  coarseness  of  texture,  and  during 
old  age  the  small  load  that  is  carried  must  be  of  very  fine  tex- 
ture or  else  must  go  off  in  solution.  Let  us  now  consider  how 
the  minimum  slope  of  a  main  river  will  be  determined. 


258  PHYSIOGRAPHIC  ESSAYS 

In  order  to  free  the  problem  from  unnecessary  complications, 
let  it  be  supposed  that  the  young  consequent  rivers  have  at  first 
slopes  that  are  steep  enough  to  make  them  all  more  than  com- 
petent to  carry  the  load  that  is  washed  into  them  from  the  wast- 
ing surface  on  either  side,  and  hence  competent  to  intrench 
themselves  beneath  the  floor  of  the  initial  troughs.  This  is  the 
condition  tacitly  postulated  in  Fig.  4,  although  it  evidently  de- 
parts from  those  cases  in  which  deformation  produces  basins 
where  lakes  must  form  and  where  deposition  (negative  denuda- 
tion) must  take  place,  and  also  from  those  cases  in  which  a 
main-trough  stream  of  moderate  slope  is,  even  in  its  youth,  over- 
supplied  with  detritus  by  active  side  streams  that  descend  steep 
and  long-wasting  surfaces ;  but  all  these  more  involved  cases 
may  be  set  aside  for  the  present. 

If  a  young  consequent  river  be  followed  from  end  to  end,  it 
may  be  imagined  as  everywhere  deepening  its  valley,  unless  at 
the  very  mouth.  Valley  deepening  will  go  on  most  rapidly  at 
some  point,  probably  nearer  head  than  mouth.  Above  this  point 
the  river  will  find  its  slope  increased  ;  below,  decreased.  Let 
the  part  upstream  from  the  point  of  most  rapid  deepening  be 
called  the  headwaters,  and  the  part  downstream  the  lower  course 
or  trunk.  In  consequence  of  the  changes  thus  systematically 
brought  about,  the  lower  course  of  the  river  will  find  its  slope 
and  velocity  decreasing  and  its  load  increasing,  that  is,  its 
ability  to  do  work  is  becoming  less,  while  the  work  that  it  has 
to  do  is  becoming  greater.  The  original  excess  of  ability  over 
work  will  thus  in  time  be  corrected,  and  when  an  equality  of 
"^  these  two  quantities  is  brought  about,  the  river  is  graded,  this 
being  a  simple  form  of  expression,  suggested  by  Gilbert,  to  re- 
place the  more  cumbersome  phrases  that  are  required  by  the 
use  of  "  profile  of  equilibrium  "  of  French  engineers.  When  the 
graded  condition  is  reached,  alteration  of  slope  can  take  place 
only  as  volume  and  load  change  their  relation ;  and  changes  of 
this  kind  are  very  slow. 

In  a  land  mass  of  homogeneous  texture  the  graded  condition 

of  a  river  would  be,  in  such  cases  as  are  above  considered,  first 

attained  at  the  mouth,  and  would  then  advance  retrogressively 

'  upstream.    When  the  trunk  streams  are  graded,  early  maturity 


THE  GEOGRAPHICAL  CYCLE 


259 


is  reached  ;  when  the  smaller  headwaters  and  side  streams  are 
also  graded,  maturity  is  far  advanced  ;  and  when  even  the  wet- 
weather  rills  are  graded,  old  age  is  attained.  In  a  land  mass  of 
heterogeneous  texture  the  rivers  will  be  divided  into  sections 
by  the  belts  of  weaker  and  stronger  rocks  that  they  traverse ; 
each  section  of  weaker  rocks  will  in  due  time  be  graded  with 
reference  to  the  section  of  harder  rock  next  downstream,  and 
thus  the  river  will  come  to  consist  of  alternating  quiet  reaches 
and  hurried  falls  or  rapids.  The  less  resistant  of  the  harder 
rocks  will  be  slowly  worn  down  to  grade  with  respect  to  the 
more  resistant  ones  that  are  farther  downstream  ;  thus  the  rapids 
will  decrease  in  number,  and  only  those  on  the  very  strongest 
rocks  will  long  survive.  Even  these  must  vanish  in  time,  and 
the  graded  condition  will  then  be  extended  from  mouth  to  head. 
The  slope  that  is  adopted  when  grade  is  assumed  varies  inversely 
with  the  volume  ;  hence  rivers  retain  steep  headwaters  long  after 
their  lower  course  is  worn  down  almost  level ;  but  in  old  age 
even  the  headwaters  must  have  a  gentle  declivity  and  moderate 
velocity,  free  from  all  torrential  features.  The  so-called  "normal 
river,"  with  torrential  headwaters  and  well-graded  middle  and 
lower  course,  is  therefore  simply  a  maturely  developed  river. 
A  young  river  may  normally  have  falls, .even  in  its  lower  course, 
and  an  old  river  must  be  free  from  rapid  movement  even  near 
its  head. 

If  an  initial  consequent  stream  is  for  any  reason  incompetent 
to  carry  away  the  load  that  is  washed  into  it,  it  cannot  degrade 
its  channel,  but  must  aggrade  instead  (to  use  an  excellent  term 
suggested  by  Salisbury).  Such  a  river  then  lays  down  the  coarser 
part  of  the  offered  load,  thus  forming  a  broadening  flood  land, 
building  up  its  valley  floor,  and  steepening  its  slope  until  it  gains 
sufficient  velocity  to  do  the  required  work.  In  this  case  the 
graded  condition  is  reached  by  filling  up  the  initial  trough  in- 
stead of  by  cutting  it  down.  Where  basins  occur,  consequent 
lakes  rise  in  them  to  the  level  of  the  outlet  at  the  lowest  point 
of  the  rim.  As  the  outlet  is  cut  down,  it  forms  a  sinking,  local 
base-level,  with  respect  to  which  the  basin  is  aggraded  ;  and  as 
the  lake  is  thus  destroyed,  it  forms  a  sinking  base-level,  with 
respect  to  which  the  tributary  streams  grade  their  valleys;  but, 


260  PHYSIOGRAPHIC  ESSAYS 

as  in  the  case  of  falls  and  rapids,  the  local  base-levels  of  outlet 
and  lake  are  temporary  and  lose  their  control  when  the  main 
drainage  lines  are  graded  with  respect  to  absolute  base-level  in 
early  or  late  maturity. 

The  Development  of  River  Branches.  Several  classes  of  side- 
streams  may  be  recognized.  Some  of  them  are  denned  by  slight 
initial  depressions  in  the  side  slopes  of  the  main  river  troughs  ; 
these  form  lateral  or  secondary  consequents,  branching  from  a 
main  consequent ;  they  generally  run  in  the  direction  of  the  dip 
of  the  strata.  Others  are  developed  by  headward  erosion  under 
the  guidance  of  weak  sub-structures  that  have  been  laid  bare  on 
the  valley  walls  of  the  consequent  streams  ;  they  follow  the  strike 
of  the  strata  and  are  entirely  regardless  of  the  form  of  the  initial 
land  surface  ;  they  may  be  called  subsequent,  this  term  having 
been  used  by  Jukes  in  describing  the  development  of  such 
streams.  Still  others  develop  here  and  there,  to  all  appearance 
by  accident,  seemingly  independent  of  systematic  guidance ; 
they  are  common  in  horizontal  or  massive  structures.  While 
waiting  to  learn  just  what  their  control  may  be,  their  independ- 
ence of  apparent  control  may  be  indicated  by  calling  them  iri; 
sequent.  Additional  classes  of  streams  are  well  known,  but  cannot 
be  described  here  for  lack  of  space. 

Relation  of  River  Ability  and  Load.  As  the  dissection  of  a 
land  mass  proceeds  with  the  fuller  development  of  its  consequent, 
subsequent,  and  insequent  streams,  the  area  of  steep  valley 
sides  greatly  increases  from  youth  into  early  and  full  maturity. 
The  waste  that  is  delivered  by  the  side  branches  to  the  main 
stream  comes  chiefly  from  the  valley  sides,  and  hence  its  quan- 
tity increases  with  the  increase  of  strong  dissection,  reaching  a 
maximum  when  the  formation  of  new  branch  streams  ceases,  or 
when  the  decrease  in  the  slope  of  the  wasting  valley  sides  comes 
to  balance  their  increase  of  area.  It  is  interesting  to  note  in 
this  connection  the  consequences  that  follow  from  two  contrasted 
relations  of  the  date  for  the  maximum  discharge  of  waste  and  of 
that  for  the  grading  of  the  trunk  streams.  If  the  first  is  not 
later  than  the  second,  the  graded  rivers  will  slowly  assume  gen- 
tler slopes  as  their  load  lessens ;  but  as  the  change  in  the  dis- 
charge of  waste  is  almost  infinitesimal  compared  to  the  amount 


THE  GEOGRAPHICAL  CYCLE  261 

discharged  at  any  one  time,  the  rivers  will  essentially  preserve 
their  graded  condition  in  spite  of  the  minute  excess  of  ability 
over  work.  On  the  other  hand,  if  the  maximum  of  load  is  not 
reached  until  after  the  first  attainment  of  the  graded  condition 
by  the  trunk  rivers,  then  the  valley  floors  will  be  aggraded  by 
the  deposition  of  a  part  of  the  increasing  load,  and  thus  a  steeper 
slope  and  a  greater  velocity  will  be  gained  whereby  the  remainder 
of  the  increase  can  be  borne  along.  The  bottom  of  the  V-shaped 
valley,  previously  carved,  is  thus  slowly  filled  with  a  gravelly 
flood  plain,  which  continues  to  rise  until  the  epoch  of  the  maxi- 
mum load  is  reached,  after  which  the  slow  degradation  above 
stated  is  entered  upon.  Early  maturity  may  therefore  witness 
a  slight  shallowing  of  the  main  valleys  instead  of  the  slight 
deepening  (indicated  by  the  dotted  line  CE  in  Fig.  4) ;  but  late 
maturity  and  all  old  age  will  be  normally  occupied  by  the  slow 
continuation  of  valley  erosion  that  was  so  vigorously  begun 
during  youth. 

The  Development  of  Divides,  There  is  no  more  beautiful 
process  to  be  found  in  the  systematic  advance  of  a  geographical 
cycle  than  the  definition,  subdivision,  and  rearrangement  of  the 
divides  (water  partings)  by  which  the  major  and  minor  drainage 
basins  are  separated.  The  forces  of  crustal  upheaval  and  defor- 
mation act  in  a  much  broader  way  than  the  processes  of  land 
sculpture ;  hence  at  the  opening  of  a  cycle  one  would  expect  to 
find  a  moderate  number  of  large  river  basins,  somewhat  in- 
definitely separated  on  the  flat  crests  of  broad  swells  or  arches 
of  land  surface,  or  occasionally  more  sharply  limited  by  the 
raised  edge  of  faulted  blocks.  The  action  of  the  lateral  con- 
sequent streams  alone  would,  during  youth  and  early  maturity, 
sharpen  all  the  vague  initial  divides  into  well-defined  consequent 
divides,  and  the  -further  action  of  insequent  and  subsequent 
streams  would  split  up  many  consequent  drainage  slopes  into 
subordinate  drainage  basins,  separated  by  subdivides,  either  inse- 
quent or  subsequent.  Just  as  the  subsequent  valleys  are  eroded 
by  their  streams  along  weak  structural  belts,  so  the  subsequent 
divides  or  ridges  stand  up  where  maintained  by  strong  struc- 
tural belts.  However  imperfect  the  division  of  drainage  areas 
and  the  discharge  of  rainfall  may  have  been  in  early  youth,  both 


262  PHYSIOGRAPHIC  ESSAYS 

are  well  developed  by  the  time  full  maturity  is  reached.  Indeed, 
the  more  prompt  discharge  of  rainfall  that  may  be  expected  to 
result  from  the  development  of  an  elaborate  system  of  sub- 
divides, and  of  slopes  from  divides  to  streams,  should  cause  an 
increased  percentage  of  run-off ;  and  it  is  possible  that  the  in- 
crease of  river  volume  thus  brought  about  from  youth  to  maturity 
may  more  or  less  fully  counteract  the  tendency  of  increase  in 
river  load  to  cause  aggradation.  But,  on  the  other  hand,  as  soon 
as  the  uplands  begin  to  lose  height,  the  rainfall  must  decrease, 
for  it  is  well  known  that  the  obstruction  to  wind  movement 
caused  by  highlands  is  an  effective  cause  of  precipitation.  While 
it  is  a  gross  exaggeration  to  maintain  that  the  Quaternary  Alpine 
glaciers  caused  their  own  destruction  by  reducing  the  height  of 
the  mountains  on  which  their  snows  were  gathered,  it  is  perfectly 
logical  to  deduce  a  decrease  of  precipitation  as  an  accompani- 
ment of  loss  of  height  from  the  youth  to  the  old  age  of  a  land 
mass.  Thus  many  factors  must  be  considered  before  the  life 
history  of  a  river  can  be  fully  analyzed. 

The  growth  of  subsequent  streams  and  drainage  areas  must 
be  at  the  expense  of  the  original  consequent  streams  and  conse- 
quent drainage  areas.  All  changes  of  this  kind  are  promoted  by 
the  occurrence  of  inclined  instead  of  horizontal  rock  layers,  and 
hence  are  of  common  occurrence  in  mountainous  regions,  but 
rare  in  strictly  horizontal  plains.  The  changes  are  also  favored 
by  the  occurrence  of  strong  contrasts  in  the  resistance  of  adja- 
cent strata.  In  consequence  of  the  migration  of  divides  thus 
caused,  many  streams  come  to  follow  valleys  that  are  worn 
down  along  belts  of  weak  strata,  while  the  divides  come  to  occupy 
the  ridges  that  stand  up  along  the  belts  of  stronger  strata ;  in 
other  words,  the  simple  consequent  drainage  of  youth  is  modified 
by  the  development  of  subsequent  drainage  lines,  so  as  to  bring 
about  an  increasing  adjustment  of  streams  to  structures,  which 
is  highly  characteristic  of  the  mature  stage  of  the  geographical 
cycle.  Not  only  so ;  adjustments  of  this  kind  form  one  of  the 
strongest,  even  if  one  of  the  latest,  proofs  of  the  erosion  of  val- 
leys by  the  streams  that  occupy  them,  and  of  the  long-continued 
action  in  the  past  of  the  slow  processes  of  weathering  and 
washing  that  are  in  operation  to-day. 


THE  GEOGRAPHICAL  CYCLE 


263 


There  is  nothing  more  significant  of  the  advance  in  geograph- 
ical development  than  the  changes  thus  brought  about.  The 
processes  here  involved  are  too  complicated  to  be  now  presented 
in  detail,  but  they  may  be  briefly  illustrated  by  taking  the  drain- 
age of  a  denuded  arch,  suggested  by  the  Jura  mountains,  as  a 
type  example.  AB  (Fig.  5)  is  a  main  longitudinal  consequent 
stream,  following  a  trough  whose  floor  has  been  somewhat  ag- 
graded by  the  waste  actively  supplied  by  the  lateral  consequents 
CD,  LO,  EF,  etc.  At  an  earlier  stage  of  denudation,  before  the 
hard  outer  layer  was  worn  away  from  the  crown  of  the  moun- 
tain arch,  all  the  lateral  consequents  headed  at  the  line  of  the 


FIG.  5 

mountain  crest.  But  guided  by  a  weak  understratum,  subsequent 
streams  77?  and  MS  have  been  developed  as  the  branches  of 
certain  lateral  consequents  £F  and  Z<9,  and  thus  the  hard  outer 
layer  has  been  undermined  and  partly  removed,  and  many  small 
lateral  consequents  have  been  beheaded.  To-day  many  of  the 
laterals,  like  JK,  have  their  source  on  the  crest  of  the  lateral 
ridge  VJQ,  and  the  headwaters,  such  as  GH,  that  once  belonged 
to  them,  are  now  diverted  by  the  subsequent  streams  to  swell 
the  volume  of  the  more  successful  laterals,  like  EF.  Similar 
changes  having  taken  place  on  the  farther  slope  of  the  moun- 
tain arch,  we  now  find  the  original  consequent  divide  of  the 
arch  crest  supplemented  by  the  subsequent  divides  formed  by 


264  PHYSIOGRAPHIC  ESSAYS 

v  the  lateral  ridges.    A  number  of  short  streams,  like  JH>  belong- 
ing to  a  class  not  mentioned  above,  run  down  the  inner  faoe 
of  the  lateral  ridges  to  a  subsequent  stream  RT.    These  short 
^streams  have  a  direction  opposite  to  that  of  the  original  con- 

\  sequents,  and  may  therefore  be  called  ohspq1  rents  As  denuda- 
tion progresses,  the  edge  of  the  lateral  ridge  will  be  worn  farther 
from  the  arch  crest ;  in  other  words,  the  subsequent  divide  will 
migrate  towards  the  main  valley,  and  thus  a  greater  length  will 
be  gained  by  the  diverted  consequent  headwaters  GH,  and  a 
greater  volume  by  the  subsequents  SM  and  RT.  During  these 
changes  the  inequality  that  must  naturally  prevail  between  ad- 
jacent successful  consequents  EF  and  LO  will  eventually  allow 
the  subsequent  branch  RT  of  the  larger  consequent  EF  to  cap- 
ture the  headwaters  ZJ/ and  SM  of  the  smaller  consequent  LO. 
In  late  maturity  the  headwaters  of  so  many  lateral  consequents 
may  be  diverted  to  swell  the  volume  of  EF  that  the  main  longi- 
tudinal consequent  above  the  point  F  may  be  reduced  to  relatively 
small  volume. 

The  Development  of  River  Meanders.    It  has  been  thus  far 

.  implied  that  rivers  cut  their  channels  vertically  downward,  but 
this  is  far  from  being  the  whole  truth.  Every  turn  in  the  course 
of  a  young  consequent  stream  causes  the  stronger  currents  to 
press  toward  the  outer  bank,  and  each  irregular,  or  perhaps  sub- 
angular,  bend  is  thus  rounded  out  to  a  comparatively  smooth 
curve.  The  river  therefore  tends  to  depart  from  its  irregular 
initial  path  (background  block  of  Fig.  6)  towards  a  serpentine 
course,  in  which  it  swings  to  right  and  left  over  a  broader  belt 
than  at  first.  As  the  river  cuts  downwards  and  outwards  at  the 
same  time,  the  valley  slopes  become  unsymmetrical  (middle  block 
of  Fig.  6),  being  steeper  on  the  side  toward  which  the  current  is 
urged  by  centrifugal  force.  The  steeper  valley  side  thus  gains 
the  form  of  a  half-amphitheater,  into  which  the  gentler-sloping 
side  enters  as  a  spur  of  the  opposite  uplands. 

When  the  graded  condition  is  attained  by  the  stream,  down- 
ward cutting  practically  ceases,  but  outward  cutting  continues ; 
a  normal  flood  plain  is  then  formed  as  the  channel  is  withdrawn 
from  the  gently  sloping  side  of  the  valley  (foreground  block  of 
Fig.  6).  Flood  plains  of  this  kind  are  easily  distinguished  in 


THE  GEOGRAPHICAL  CYCLE 


265 


their  early  stages  from  those  already  mentioned  (formed  by 
aggrading  the  flat  courses  of  incompetent  young  rivers,  or  by 
aggrading  the  graded  valleys  of  overloaded  rivers  in  early  ma- 
turity); for  these  occur  in  detached  lunate  areas,  first  on  one 
side,  then  on  the  other  side,  of  the  stream,  and  always  system- 
atically placed  at  the  foot  of  the  gentler-sloping  spurs.  But 
as  time  passes,  the  river  impinges  on  the  upstream  side  and 
withdraws  from  the  downstream  side  of  every  spur,  and  thus 
the  spurs  are  gradually  consumed ;  they  are  first  sharpened, 
so  as  better  to  deserve  their  name ;  they  are  next  reduced  to 
short  cusps ;  then  they  are  worn  back  to  blunt  salients ;  and, 
finally,  they  are  entirely  consumed,  and  the  river  wanders  freely 
on  its  open  flood  plain,  occasionally  swinging  against  the  valley 


FIG.  6 


side,  now  here,  now  there.  By  this  time  the  curves  of  youth  are 
changed  into  systematic  meanders,  of  radius  appropriate  to  river 
volume ;  and  for  all  the  rest  of  an  undisturbed  life  the  river 
persists  in  the  habit  of  serpentine  flow.  The  less  the  slope  of 
the  flojDjd  jDlain  becomes  in  advancing  old  age,  the  larger  the 
arc  of  each  meander,  and  hence  the  longer  the  course  of  the 
river  from  any  point  to  its  mouth.  Increase  of  length  from  this 
cause  must  tend  to  diminish  fall,  and  thus  to  render  the  river 
less  competent  than  it  was  before  ;  and  the  result  of  this  tend- 
ency will  be  to  retard  the  already  slow  process  by  which  a 
gently  sloping  flood  plain  is  degraded,  so  as  to  approach  coin- 
cidence with  a  level  surface ;  but  it  is  not  likely  that  old  rivers 
often  remain  undisturbed  long  enough  for  the  full  realization  of 
these  theoretical  conditions. 


266  PHYSIOGRAPHIC  ESSAYS 

The  migration  of  divides  must  now  and  then  result  in  a  sud- 
den increase  in  the  volume  of  one  river  and  in  a  correspondingly 
sudden  decrease  of  another.  After  such  changes,  accommodation 
to  the  changed  volume  must  be  made  in  the  meanders  of  each 
river  affected.  The  one  that  is  increased  will  call  for  enlarged 
dimensions  ;  it  will  usually  adopt  a  gentler  slope,  thus  terracing 
its  flood  plain,  and  demand  a  greater  freedom  of  swinging,  thus 
widening  its  valley.  The  one  that  is  decreased  will  have  to  be 
satisfied  with  smaller  dimensions ;  it  will  wander  aimlessly  in 
relatively  minute  meanders  on  its  flood  plain,  and  from  increase 
of  length,  as  well  as  from  loss  of  volume,  it  will  become  incom- 
petent to  transport  the  load  brought  in  by  the  side  streams, 
and  thus  its  flood  plain  must  be  aggraded.  There  are  beautiful 
examples  known  of  both  of  these  peculiar  conditions. 

The  Development  of  Graded  Valley  'Sides.  When  the  migra- 
tion of  divides  ceases  in  late  maturity,  and  the  valley  floors  of 
the  adjusted  streams  are  well  graded,  even  far  toward  the  head- 
waters, there  is  still  to  be  completed  another  and  perhaps  even 
more  remarkable  sequence  of  systematic  changes  than  any  yet 
described  :  this  is  the  development  of  graded  waste  slopes  on 
the  valley  sides.  ( It  is  briefly  stated  that  valleys  are  eroded  by 
their  rivers,  yet  there  is  a  vast  amount  of  work  performed  in 
the  erosion  of  valleys  in  which  rivers  have  no  part.  It  is  true 
that  rivers  deepen  the  valleys  in  the  youth  and  widen  the  val- 
ley floors  during  the  maturity  and  old  age  of  a  cycle,  and  that 
they  carry  to  the  sea  the  waste  denuded  from  the  land  ;  it  is 
this  work  of  transportation  to  the  sea  that  is  peculiarly  the 
function  of  rivers,  but  the  material  to  be  transported  is  sup- 
plied chiefly  by  the  action  of  the  weather  on  the  steeper  conse- 
quent slopes  and  on  the  valley  sides.  The  transportation  of  the 
weathered  material  from  its  source  to  the  stream  in  the  valley 
bottom  is  the  work  of  various  slow-acting  processes,  such  as 
the  surface  wash  of  rain,  the  action  of  ground  water,  changes 
of  temperature,  freezing  and  thawing,  chemical  disintegration 
and  hydration,  the  growth  of  plant  roots,  the  activities  of  bur- 
rowing animals.  All  these  cause  the  weathered  rock  waste  to 
wash  and  creep  slowly  downhill,  and  in  the  motion  thus  ensuing 
there  is  much  that  is  analogous  to  the  flow  of  a  river.  Indeed, 


THE  GEOGRAPHICAL  CYCLE.  267. 

when  considered  in  a  very  broad  and  general  way,  a  river  is 
seen  to  be  a  moving  mixture  of  water  and  waste  in  variable 
proportions,  but  mostly  water ;  while  a  creeping  sheet  of  hill- 
side waste  is  a  moving  mixture  of  waste  and  water  in  variable 
proportions,  but  mostly  waste.  Although  the  river  and  the  hill- 
side waste  sheet  do  not  resemble  each  other  at  first  sight,  they 
are  only  the  extreme  members  of  a  continuous  series,  and  when 
this  generalization  is  appreciated,  one  may  fairly  extend  the 
"river  "  all  over  its  basin  and  up  to  its  very  divides.  Ordinarily 
treated,  the  river  is  like  the  veins  of  a  leaf ;  broadly  viewed,  it 
is  like  the  entire  leaf.  The  verity  of  this  comparison  may  be 
more  fully  accepted  when  the  analogy,  indeed  the  homology,  of 
waste  sheets  and  water  streams  is  set  forth. 

In  the  first  place,  a  waste  sheet  moves  fastest  at  the  surface 
and  slowest  at  the  bottom,  like  a  water  stream.  A  graded  waste 
sheet  may  be  defined  in  the  very  terms  applicable  to  a  graded 
water  stream  ;  it  is  one  in  which  the  ability  of  the  transporting 
forces  to  do  work  is  equal  to  the  work  that  they  have  to  do. 
This  is  the  condition  that  obtains  on  those  evenly  slanting, 
waste-covered  mountain  sides  which  have  been  reduced  to  a 
slope  that  engineers  call  "  the  angle  of  repose,"  because  of  the 
apparently  stationary  condition  of  the  creeping  waste,  but  that 
should  be  called,  from  the  physiographic  standpoint,  "the  angle 
of  first-developed  grade."  The  rocky  cliffs  and  ledges  that 
often  surmount  graded  slopes  are  not  yet  graded  ;  waste  is  re- 
moved from  them  faster  than  it  is  supplied  by  local  weathering 
and  by  creeping  from  still  higher  slopes,  and  hence  the  cliffs 
and  ledges  are  left  almost  bare ;  they  correspond  to  falls  and 
rapids  in  water  streams,  where  the  current  is  so  rapid  that  its 
cross  section  is  much  reduced.  A  hollow  on  an  initial  slope 
will  be  filled  to  the  angle  of  grade  by  waste  from  above ;  the 
waste  will  accumulate  until  it  reaches  the  lowest  point  on  the 
rim  of  the  hollow,  and  then  outflow  of  waste  will  balance  in- 
flow ;  and  here  is  the  evident  homologue  of  a  lake. 

In  the  second  place,  it  will  be  understood,  from  what  has 
already  been  said,  that  rivers  normally  grade  their  valleys  retro- 
gressively  from  the  mouth  head  wards,  and  that  small  side 
streams  may  not  be  graded  till  long  after  the  trunk  river  is 


268  PHYSIOGRAPHIC  ESSAYS 

graded.  So  with  waste  sheets  ;  they  normally  begin  to  establish 
a  graded  condition  at  their  base  and  then  extend  it  up  the 
slope  of  the  valley  side  whose  waste  they  "  drain."  When  rock 
masses  of  various  resistance  are  exposed  on  the  valley  side,  each 
one  of  the  weaker  is  graded  with  reference  to  the  stronger  one 
next  downhill,  and  the  less  resistant  of  the  stronger  ones  are 
graded  with  reference  to  the  more  resistant,  or  with  reference  to 
the  base  of  the  valley  side ;  this  is  perfectly  comparable  to  the 
development  of  graded  stretches  and  to  the  extinction  of  falls 
and  rapids  in  rivers.  Ledges  remain  ungraded  on  ridge  crests  and 
on  the  convex  front  of  hill  spurs  long  after  the  graded  condi- 
tion is  reached  in  the  channels  of  wet-weather  streams  in  the 
ravines  between  the  spurs  ;  this  corresponds  nicely  with  the 
slower  attainment  of  grade  in  small  side  streams  than  in  large 
trunk  rivers.  ^But  as  late  maturity  passes  into  old  age,  even 
the  ledges  on  ridge  crests  and  spur  fronts  disappear,  all  being 
concealed  in  a  universal  sheet  of  slowly  creeping  waste.  From 
any  point  on  such  a  surface  a  graded  slope  leads  the  waste 
down  to  the  streams.  At  any  point  the  agencies  of  removal  are 
just  able  to  cope  with  the  waste  that  is  there  weathered  plus 
that  which  comes  from  farther  uphill.  This  wonderful  condition 
is  reached  in  certain  well-denuded  mountains,  now  subdued 
from  their  mature  vigor  to  the  rounded  profiles  of  incipient  old 
age.  When  the  full  meaning  of  their  graded  form  is  appre- 
hended, it  constitutes  one  of  the  strongest  possible  arguments 
for  the  sculpture  of  the  lands  by  the  slow  processes  of  weather- 
ing long  continued.  To  look  upon  a  landscape  of  this  kind 
without  any  recognition  of  the  labor  expended  in  producing  it, 
or  of  the  extraordinary  adjustments  of  streams  to  structures 
and  of  waste  to  weather,  is  like  visiting  Rome  in  the  ignorant 
belief  that  the  Romans  of  to-day  have  had  no  ancestors. 

Just  as  graded  rivers  slowly  degrade  their  courses  after  the 
period  of  maximum  load  is  past,  so  graded  waste  sheets  adopt 
gentler  and  gentler  slopes  when  the  upper  ledges  are  consumed 
and  coarse  waste  is  no  longer  plentifully  shed  to  the  valley  sides 
below.  A  changing  adjustment  of  a  most  delicate  kind  is  here 
discovered.  When  the  graded  slopes  are  first  developed  they 
are  steep,  and  the  waste  that  covers  them  is  coarse  and  of 


THE  GEOGRAPHICAL  CYCLE  269 

•moderate  thickness ;.  here  the  strong  agencies  of  removal  have 
all  they  can  do  to  dispose  of  the  plentiful  supply  of  coarse  waste 
from  the  strong  ledges  above,  and  the  no  less  plentiful  supply 
of  waste  that  is  weathered  from  the  weaker  rocks  beneath  the 
thin  cover  of  detritus.  In  a  more  advanced  stage  of  the  cycle 
the  graded  slopes  are  moderate,  and  the  waste  that  covers  them 
is  of  finer  texture  and  greater  depth  than  before;  here  the 
weakened  agencies  of  removal  are  favored  by  the  slower 
weathering  of  the  rocks  beneath  the  thickened  waste  cover,  and 
by  the  greater  refinement  (reduction  to  finer  texture)  of  the 
loose  waste  during  its  slow  journey.  In  qld_age,  when  all  the 
slopes  are  very  gentle,  the  agencies  of  waste  removal  must 
everywhere  be  weak,  and  their  equality  with  the  processes  of 
waste  supply  can  be  maintained  only  by  the  reduction  of  the 
latter  to  very  low  values.  The  waste  sheet  then  assumes  a  great 
thickness,  —  even  fifty  or  a  hundred  feet,  —  so  that  the  progress 
of  weathering  is  almost  nil;  at  the  same  time,  the  surface  waste 
is  reduced  to  extremely  fine  texture,  so  that  some  of  its  particles 
may  be  moved  even  on  faint  slopes.  Hence  the  occurrence  of 
deep  soils  is  an  essential  feature  of  old  age,  just  as  the  occurrence 
of  bare  ledges  is  of  youth.  The  relationships  here  obtaining  are 
as  significant  as  those  which  led  Playfair  to  his  famous  statement 
concerning  the  origin  of  valleys  by  the  rivers  that  drain  them. 

Old  Age.  Maturity  is  passed  and  old  age  is  fully  entered 
upon  when  the  hilltops  and  the  hillsides,  as  well  as  the  valley 
floors,  are  graded.  No  new  features  are  now  developed,  and 
those  that  have  been  earlier  developed  are  weakened  or  even 
lost.  The  search  for  weak  structures  and  the  establishment  of 
valleys  along  them  has  already  been  thoroughly  carried  out ; 
now  the  larger  streams  meander  freely  in  open  valleys  and  begin 
to  wander  away  from  the  adjustments  of  maturity.  The  active 
streams  of  the  time  of  greatest  relief  now  lose  their  headmost 
branches,  for  the  rainfall  is  lessened  by  the  destruction  of  the 
highlands,  and  the  run-off  of  the  rain  water  is  retarded  by  the 
flat  slopes  and  deep  soils.  The  landscape  is  slowly  tamed  from 
its  earlier  strength  and  presents  only  a'  succession  of  gently 
rolling  swells  alternating  with  shallow  valleys,  a  surface  every- 
where open  to  occupation.  As  time  passes,  the  relief  becomes 


270  PHYSIOGRAPHIC  ESSAYS 

less  and  less ;  whatever  the  uplifts  of  youth,  whatever  the  dis- 
order and  hardness  of  the  rocks,  an  almost  featureless  plain 
(a  peneplain),  showing  little  sympathy  with  structure,  and  con- 
trolled only  by  a  close  approach  of  base-level,  must  characterize 
the  penultimate  stage  of  the  uninterrupted  cycle ;  and  the  ulti- 
mate stage  would  be  a  plain  without  relief. 

Some  observers  have  doubted  whether  even  the  penultimate 
stage  of  a  cycle  is  ever  reached,  so  frequently  do  movements  in 
the  earth's  crust  cause  changes  in  its  position  with  respect  to 
base-level.  But,  on  the  other  hand,  there  are  certain  regions  of 
greatly  disordered  structure  whose  small  relief  and  deep  soils 
cannot  be  explained  without  supposing  them  to  have,  in  effect, 
passed  through  all  the  stages  above  described  —  and  doubtless 
many  more,  if  the  whole  truth  were  told  —  before  reaching  the 
penultimate,  whose  features  they  verify.  In  spite  of  the  great 
disturbances  that  such  regions  have  suffered  in  past  geological 
periods,  they  have  afterwards  stood  still  so  long,  so  patiently, 
as  to  be  worn  down  to  peneplains  over  large  areas,  only  here 
and  there  showing  residual  reliefs  where  the  most  resistant 
rocks  still  stand  up  above  the  general  level.  Thus  verification 
is  found  for  the  penultimate,  as  well  as  for  many  earlier  stages, 
of  the  ideal  cycle.  Indeed,  although  the  scheme  of  the  cycle  is 
here  presented  only  in  theoretical  form,  the  progress  of  develop- 
mental changes  through  the  cycle  has  been  tested  over  and 
over  again  for  many  structures  and  for  various  stages ;  and  on 
recognizing  the  numerous  accordances  that  are  discovered  when 
the  consequences  of  theory  are  confronted  with  the  facts  of 
observation,  one  must  feel  a  growing  belief  in  the  verity  and 
value  of  the  theory  that  leads  to  results  so  satisfactory. 

It  is  necessary  to  repeat  what  has  already  been  said  as  to  the 
practical  application  of  the  principles  of  the  geographical  cycle. 
Its  value  to  the  geographer  is  not  simply  in  giving  explanation 
to  land  forms  ;  its  greater  value  is  in  enabling  him  to  see  what 
he  looks  at  and  to  say  what  he  sees.  His  standards  of  com- 
parison, by  which  the  unknown  are  likened  to  the  known,  are 
greatly  increased  over  the  short  list  included  in  the  terminology 
of  his  school  days.  Significant  features  are  consciously  sought 
for ;  exploration  becomes  more  systematic  and  less  haphazard. 


THE  GEOGRAPHICAL  CYCLE  271 

"A  hilly  region"  of  the  unprepared  traveler  becomes  (if  such 
it  really  be)  "a  maturely  dissected  upland"  in  the  language  of 
the  better-prepared  traveler ;  and  the  reader  of  travels  at  home 
gains  greatly  by  the  change.  "A  hilly  region"  brings  no 
definite  picture  before  the  mental  eyes.  "A  maturely  dissected 
upland  "  suggests  a  systematic  association  of  well-defined  fea- 
tures ;  all  the  streams  at  grade,  except  the  small  headwaters  ; 
the  larger  rivers  already  meandering  on  flood-plained  valley 
floors ;  the  upper  branches  ramifying  among  spurs  and  hills, 
whose  flanks  show  a  good  beginning  of  graded  slopes  ;  the  most 
resistant  rocks  still  cropping  out  in  ungraded  ledges,  whose  ar- 
rangement suggests  the  structure  of  the  region.  The  practical 
value  of  this  kind  of  theoretical  study  seems  to  me  so  great 
that,  among  various  lines  of  work  that  may  be  encouraged  by 
the  councils  of  the  great  geographical  societies,  I  believe  there 
is  none  that  would  bring  larger  reward  than  the  encouragement 
of  some  such  method  as  is  here  outlined  for  the  systematic 
investigation  of  land  forms. 

Some  geographers  urge  that  it  is  dangerous  to  use  the  theo- 
retical or  explanatory  terminology  involved  in  the  practical  ap- 
plication of  the  principles  of  the  geographical  cycle ;  mistakes 
may  be  made,  and  harm  would  thus  be  done.  There  are  various 
sufficient  answers  to  this  objection.  A  very  practical  answer  is 
that  suggested  by  Penck,  to  the  effect  that  a  threefold  terminol- 
ogy should  be  devised,  — one  set  of  terms  being  purely  empirical, 
as  "  high,"  "  low,"  "  cliff,"  "  gorge,"  "  lake,"  "  island  "  ;  another 
set  being  based  on  structural  relations,  as  "monoclinal  ridge," 
"transverse  valley,"  "  lava-capped  mesa";  and  the  third  being 
reserved  for  explanatory  relations,  as  "  mature  dissection,"  "  ad- 
justed drainage,"  "  graded  slopes."  Another  answer  is  that  the 
explanatory  terminology  is  not  really  a  novelty,  but  only  an  at- 
tempt to  give  a  complete  and  systematic  expansion  to  a  rather 
timid  beginning  already  made  :  a  sand  dune  is  not  simply  a  hill- 
ock of  sand,  but  a  hillock  heaped  by  the  wind  ;  a  delta  is  not 
simply  a  plain  at  a  river  mouth,  but  a  plain  formed  by  river 
action ;  a  volcano  is  not  simply  a  mountain  of  somewhat  conical 
form,  but  a  mountain  formed  by  eruption.  It  is  chiefly  a  matter 
of  experience  and  temperament  where  a  geographer  ceases  to 


272  PHYSIOGRAPHIC  ESSAYS 

apply  terms  of  this  kind.  But  little  more  than  half  a  century 
ago  the  erosion  of  valleys  by  rivers  was  either  doubted  or  not 
thought  of  by  the  practical  geographer ;  to-day  the  mature  ad- 
justment of  rivers  to  structures  is  in  the  same  position ;  and 
here  is  the  third,  and  to  my  mind  the  most  important,  answer 
to  those  conservatives  who  would  maintain  an  empirical  posi- 
tion for  geography  instead  of  pressing  forward  toward  the 
rational  and  explanatory  geography  of  the  future.  It  cannot 
be  doubted,  in  view  of  what  has  already  been  learned  to-day, 
that  an  essentially  explanatory  treatment  must  in  the  next 
century  be  generally  adopted  in  all  branches  of  geographical 
study ;  it  is  full  time  that  an  energetic  beginning  should  be 
made  toward  so  desirable  an  end. 

Interruptions  of  the  Ideal  Cycle.  One  of  the  first  objections 
that  might  be  raised  against  a  terminology  based  on  the  se- 
quence of  changes  through  the  ideal  uninterrupted  cycle  is 
that  such  a  terminology  can  have  little  practical  application  on 
an  earth  whose  crust  has  the  habit  of  rising  and  sinking  fre- 
quently during  the  passage  of  geological  time.  To  this  it  may 
be  answered  that  if  the  scheme  of  the  geographical  cycle  were 
so  rigid  as  to  be  incapable  of  accommodating  itself  to  the  actual 
condition  of  the  earth's  crust,  it  would  certainly  have  to  be  aban- 
doned as  a  theoretical  abstraction ;  but  such  is  by  no  means  the 
case.  Having  traced  the  normal  sequence  of  events  through  an 
ideal  cycle,  our  next  duty  is  to  consider  the  effects  of  any  and 
all  kinds  of  movements  of  the  land  mass  with  respect  to  its 
base-level.  Such  movements  must  be  imagined  as  small  or 
great,  simple  or  complex,  rare  or  frequent,  gradual  or  rapid, 
early  or  late.  Whatever  their  character,  they  will  be  called 
"  interruptions,"  because  they  determine  a  more  or  less  com- 
plete break  in  processes  previously  in  operation,  by  beginning  a 
new  series  of  processes  with  respect  to  the  new  base-level. 
Whenever  interruptions  occur,  the  preexistent  conditions  that 
they  interrupt  can  be  understood  only  after  one  has  analyzed 
them  in  accordance  with  the  principles  of  the  cycle,  and  herein 
lies  one  of  the  most  practical  applications  of  what  at  firs't  seems 
remotely  theoretical.  A  land  mass,  uplifted  to  a  greater  altitude 
than  it  had  before,  is  at  once  more  intensely  attacked  by  the 


THE  GEOGRAPHICAL  CYCLE  273 

denuding  processes  in  the  new  cycle  thus  initiated  ;  but  the 
forms  on  which  the  new  attack  is  made  can  only  be  under- 
stood by  considering  what  had  been  accomplished  in  the  pre- 
ceding cycle  previous  to  its  interruption.  It  will  be  possible 
here  to  consider  only  one  or  two  specific  examples  from  among 
the  multitude  of  interruptions  that  may  be  imagined. 

Let  it  be  supposed  that  a  maturely  dissected  land  mass  is 
evenly  uplifted  five  hundred  feet  above  its  former  position. 
All  the  graded  streams  are  hereby  revived  to  new  activities, 
and  proceed  to  intrench  their  valley  floors,  in  order  to  develop 
graded  courses  with  respect  to  the  new  base-level.  The  larger 
streams  first  show  the  effect  of  the  change;  the  smaller  streams 
follow  suit  as  rapidly  as  possible.  Falls  reappear  for  a  time  in 
the  river  channels  and  then  are  again  worn  away.  Adjustments 
of  streams  to  structures  are  carried  farther  in  the  second  effort 
of  the  new  cycle  than  was  possible  in  the  single  effort  of 
the  previous  cycle.  Graded  hillsides  are  undercut ;  the  waste 
washes  and  creeps  down  from  them,  leaving  a  long,  even  slope 
of  bare  rock ;  the  rocky  slope  is  hacked  into  an  uneven  face  by 
the  weather  until  at  last  a  new  graded  slope  is  developed.  Cliffs 
that  had  been  extinguished  on  graded  hillsides  in  the  previous 
cycle  are  thus  for  a  time  brought  to  life  again,  like  the  falls  in  the 
rivers,  only  to  disappear  in  the  late  maturity  of  the  new  cycle. 

The  combination  of  topographical  features  belonging  to  two 
cycles  may  be  called  comrjQsite-tapDgraph^,  and  many  examples 
could  be  cited  in  illustration  of  this  interesting  association.  In 
every  case,  description  is  made  concise  and  effective  by  employ- 
ing a  terminology  derived  from  the  scheme  of  the  cycle.  For 
example,  Normandy  is  an  uplifted  peneplain,  hardly  yet  in  the 
mature  stage  of  its  new  cycle ;  thus  stated,  explanation  is  con- 
cisely given  to  the  meandering  course  of  the  rather  narrow  valley 
of  the  Seine,  for  this  river  has  carried  forward  into  the  early 
stages  of  the  new  cycle  the  habit  of  swinging  in  strong  meanders 
that  it  had  learned  in  the  later  stages  of  the  former  cycle.  - 

If  the  uplift  of  a  dissected  region  be  accompanied  by  a  gentle 
tilting,  then  all  the  water  streams  and  waste  streams  whose  slope 
is  increased  will  be  revived  to  new  activity,  while  all  those  whose 
slope  is  decreased  will  become  less  active.  The  divides  will 


274  PHYSIOGRAPHIC  ESSAYS 

migrate  into  the  basins  of  the  less  active  streams,  and  the  revived 
streams  will  gain  length  and  drainage  area.  If  the  uplift  be  in 
the  form  of  an  arch,  some  of  the  weaker  streams  whose  course 
is  across  the  axis  of  the  arch  may  be,  as  it  were,  "  broken  in 
half  "  ;  a  reversed  direction  of  flow  may  thus  be  given  to  one 
part  of  the  broken  stream  ;  but  the  stronger  rivers  may  still  per- 
severe across  the  rising  arch  in  spite  of  its  uplift,  cutting  down 
their  channels  fast  enough  to  maintain  their  direction  of  flow  un- 
changed ;  and  such  rivers  are  known  as  antecedent  rivers. 

The  changes  introduced  by  an  interruption  involving  depres- 
sion are  easily  deduced.  Among  their  most  interesting  features 
is  the  invasion  of  the  lower  valley  floors  by  the  sea,  thus  "  drown- 
ing "  the  valleys  to  a  certain  depth  and  converting  them  into 
bays.  Movements  that  tend  to  produce  trough-like  depres- 
sions across  the  course  of  a  river  usually  give  birth  to  a  lake 
of  water  or  waste  in  the  depressed  part  of  the  river  valley.  In 
mountain  ranges  frequent  and  various  interruptions  occur  dur- 
ing the  long  period  of  deformation ;  the  Alps  show  so  many 
recent  interruptions  that  a  student  there  would  find  little  use 
for  the  ideal  cycle ;  but  in  mountain  regions  of  ancient  de- 
formation the  disturbing  forces  seem  to  have  become  almost 
extinct,  and  there  the  ideal  cycle  is  almost  realized.  Central 
France  gives  good  illustration  of  this  principle.  It  is  manifest 
that  one  might  imagine  an  endless  number  of  possible  combina- 
tions among  the  several  factors  of  structure,  stage  of  develop- 
ment at  time  of  interruption,  character  of  interruption,  and 
time  since  interruption ;  but  space  cannot  be  here  given  to 
their  further  consideration. 

Accidental  Departures  from  the  Ideal  Cycle.  Besides  the  in- 
terruptions that  involve  movements  of  a  land  mass  with  respect 
to  base-level,  there  are  two  other  classes  of  departure  from  the 
normal  or  ideal  cycle  that  do  not  necessarily  involve  any  such 
movements  :  these  are  changes  of  climate  and  volcanic  erup- 
tions, both  of  which  occur  so  arbitrarily  as  to  place  and  time 
that  they  may  be  called  accidents.  Changes  of  climate  may 
vary  from  the  normal  toward  the  frigid  or  the  arid,  each  change 
causing  significant  departures  from  normal  geographical  develop- 
ment. If  a  reverse  change  of  climate  brings  back  more  normal 


THE  GEOGRAPHICAL  CYCLE  275 

conditions,  the  effects  of  the  abnormal  accident  may  last  for 
some  small  part  of  a  cycle's  duration  before  they  are  obliterated. 
It  is  here  that  features  of  glacial  origin  belong,  so  common  in 
northwestern  Europe  and  northeastern  America.  Judging  by 
the  present  analysis  of  glacial  and  interglacial  epochs  during 
Quaternary  time,  or  of  humid  and  arid  epochs  in  the  Great  j 
Salt  Lake  region,  it  must  be  concluded  that  accidental  changes 
may  occur  over  and  over  again  within  a  single  cycle. 

In  brief  illustration  of  the  combined  interruptions  and  acci- 
dents, it  may  be  said  that  southern  New  England  is  an  old 
mountain  region  which  had  been  reduced  to  a  pretty  good 
peneplain  when  further  denudation  was  interrupted  by  a  slant- 
ing uplift,  with  gentle  descent  to  the  southeast;  that  in  the 
cycle  thus  introduced  the  tilted  peneplain  was  denuded  to  a 
sub-mature  or  late-mature  stage  (according  to  the  strength  or 
weakness  of  its  rocks) ;  and  that  the  maturely  dissected  region 
was  then  glaciated  and  slightly  depressed  so  recently  that  little 
change  has  happened  since.  An  instructive  picture  of  the  region 
may  be  conceived  from  this  brief  description. 

Many  volcanic  eruptions  produce  forms  so  large  that  they  de- 
serve to  be  treated  as  new  structural  regions,  but  when  viewed 
in  a  more  general  way,  a  great  number  of  eruptions,  if  not  the 
greater  number,  produce  forms  of  small  dimensions  compared 
to  those  of  the  structures  on  which  they  are  superposed  ;  the 
volcanoes  of  central  France  are  good  instances  of  this  relation. 
Thus  considered,  volcanoes  and  lava  flows  are  so  arbitrarily 
placed  in  time  and  space  that  their  classification  under  the  head 
of  accidents  is  warranted.  Still  further  ground  for  this  classi- 
fication is  found  when  the  effects  of  a  volcanic  eruption  on  the 
preexistent  processes  of  land  sculpture  are  examined.  A  valley 
may  be  blockaded  by  a  growing  cone  and  its  lava  flows  ;  lakes 
may  form  in  the  upstream  portion  of  such  a  valley,  even  if  it  be 
mature  or  old.  If  the  blockade  be  low,  the  lake  will  overflow  to 
one  side  of  the  barrier,  and  thus  the  river  will  be  locally  displaced 
from  its  former  course,  however  well  adjusted  to  a  weak  struc- 
ture that  course  may  have  been.  If  the  blockade  be  higher  than 
some  points  on  the  headwater  divides,  the  lake  will  overflow 
"  backward  "  and  the  upper  part  of  the  river  system  will  become 


276  PHYSIOGRAPHIC  ESSAYS 

tributary  to  an  adjacent  system.  The  river  must  cut  a  gorge 
across  the  divide,  however  hard  the  rocks  are  there  ;  thus  sys- 
tematic adjustments  to  structure  are  seriously  interfered  with, 
and  accidental  relations  are  introduced.  The  form  of  the  volcanic 
cone  and  the  sprawling  flow  of  its  lava  streams  are  quite  out  of 
accord  with  the  forms  that  characterize  the  surrounding  region. 
The  cone  arbitrarily  forms  a  mountain,  even  though  the  subjacent 
rocks  may  be  weak ;  the  lava  flows  aggrade  valleys  that  should 
be  degraded.  During  the  dissection  of  the  cone,  a  process  that  is 
systematic  enough  if  considered  for  itself  alone,  a  radial  arrange- 
ment of  spurs  and  ravines  will  be  developed  ;  in  long  future  time 
the  streams  of  such  ravines  may  cut  down  through  the  volcanic 
structures  and  thus  superpose  themselves  most  curiously  on  the 
underlying  structures.  The  lava  flows,  being  usually  more  resist- 
ant than  the  rocks  of  the  district  that  they  invade,  gain  a  local 
relief  as  the  adjoining  surface  is  lowered  by  denudation  ;  thus  an 
inversion  of  topography  is  brought  about,  and  a  "  table  moun- 
tain" comes  to  stand  where  formerly  there  had  been  the  valley 
that  guided  the  original  course  of  the  lava  flow.  The  table  moun- 
tain may  be  quite  isolated  from  its  volcanic  source,  where  the 
cone  is  by  this  time  reduced  to  a  knob  or  butte.  But  although 
these  various  considerations  seem  to  me  to  warrant  the  classi- 
fication of  volcanic  forms  as  accidental,  in  contrast  to  the 
systematic  forms  with  which  they  are  usually  associated,  great 
importance  should  not  be  attached  to  this  method  of  arrange- 
ment ;  it  should  be  given  up  as  soon  as  a  more  truthful  or  more 
convenient  classification  is  introduced. 

The  Forms  assumed  by  Land  Waste.  An  extension  of  the 
subject  treated  in  the  section  on  "  Graded  Valley  Sides  "  would 
lead  to  a  general  discussion  of  the  forms  assumed  by  the  waste 
of  the  land  on  the  way  to  the  sea,  —  one  of  the  most  interesting 
and  profitable  topics  for  investigation  that  has  come  under  my 
notice.  Geographers  are  well  accustomed  to  giving  due  consid- 
eration to  the  forms  assumed  by  the  water  drainage  of  the  land 
on  the  way  to  the  sea,  and  a  good  terminology  is  already  in  use 
for  naming  them  ;  but  much  less  consideration  is  given  to  the 
forms  assumed  by  the  waste  that  slowly  moves  from  the  land 
to  the  sea.  They  are  seldom  presented  in  their  true  relations ; 


THE  GEOGRAPHICAL  CYCLE  277 

many  of  them  have  no  generally  accepted  names,  —  for  example, 
the  long  slopes  of  waste  that  reach  forward  from  the  mountains 
into  the  desert  basins  of  Persia.  Forms  as  common  as  alluvial 
fans  are  unmentioned  in  all  but  the  most  recent  schoolbooks ; 
and  such  features  as  till  plains,  moraines,  and  drumlins  are  usu- 
ally given  over  to  the  geologist,  as  if  the  geographer  had  nothing 
to  do  with  them  !  There  can  be  no  question  of  the  great  impor- 
tance of  waste  forms  to  the  geographer,  but  it  is  not  possible 
here  to  enter  into  their  consideration.  Suffice  it  to  say  that  waste 
forms  constitute  a  geographical  group  which,  like  water  forms, 
stand  quite  apart  from  such  groups  as  mountains  and  plateaus. 
The  latter  are  forms  of  structure,  and  should  be  classified  accord- 
ing to  the  arrangement  of  their  rocks  and  to  their  age  or  stage 
of  development  The  former  are  forms  of  process,  and  should 
be  classified  according  to  the  processes  involved  and  to  the  stage 
that  they  have  reached.  The  application  of  this  general  principle 
gives  much  assistance  in  the  description  of  actual  landscapes. 

Lack  of  space  prevents  due  consideration  here  of  the  develop- 
ment of  shore-lines,  a  subject  not  less  interesting,  suggestive, 
and  helpful  than  the  development  .of  inland  forms ;  but  I  shall 
hope  to  return  on  some  later  occasion  to  a  discussion  of  shore 
features,  when  it  may  be  found  that  much  of  the  terminology 
already  introduced  is  again  applicable.  In  closing  this  article  I 
must  revert,  even  though  for  a  third  time,  to  the  practical  side  of 
the  theoretical  cycle,  with  its  interruptions  and  accidents.  It  can- 
not be  too  carefully  borne  in  mind  that  the  explanation  of  the 
origin  of  land  forms  is  not  for  its  own  sake  added  to  the  study 
of  geography,  but  for  the  sake  of  the  aid  that  explanation  gives 
to  the  observation  and  description  of  existing  geographical  fea- 
tures. The  sequence  of  forms  developed  through  the  cycle  is  not 
an  abstraction  that  one  leaves  at  home  when  he  goes  abroad ;  it 
is  literally  a  vade  mecum  of  the  most  serviceable  kind.  During 
my  visits  in  Europe  the  scheme  and  the  terminology  of  the  cycle 
have  been  of  the  greatest  assistance  in  my  studies.  Application  of 
both  scheme  and  terminology  is  found  equally  well  in  the  minute 
and  infantile  coastal  plains  that  border  certain  stretches  of  the 
Scotch  shore-line  in  consequence  of  the  slight  post-glacial  eleva- 
tion of  the  land,  and  in  the  broad  and  aged  central  plateau  of 


278  PHYSIOGRAPHIC  ESSAYS 

France,  where  the  young  valleys  of  to-day  result  from  the  uplift 
of  the  region  and  the  revival  of  its  rivers  after  they  had  sub- 
maturely  dissected  a  preexistent  peneplain.  The  adjustments  of 
streams  to  structures  brought  about  by  the  interaction  of  the 
waxing  Severn  and  the  waning  Thames  prove  to  be  even  more 
striking  than  when  I  first  noticed  them  in  1894.  The  large 
ancient  delta  of  the  Var,  between  Nice  and  Cannes,  now  uplifted 
more  than  two  hundred  meters  and  maturely  dissected,  must 
come  to  be  the  type  example  of  this  class  of  forms.  The  Italian 
Riviera,  west  of  Genoa,  may  be  concisely  described  as  a  region 
of  subdued  mountains  that  has  been  partly  submerged  and  that 
is  now  approaching  maturity  of  shore -line  features  in  the  cycle 
thus  initiated  ;  one  may  picture,  from  this  brief  statement,  the 
mountain  spurs  with  well-graded  slopes,  limited  by  a  very  irreg- 
ular shore-line  when  first  depressed,  but  now  fronting  in  a  com- 
paratively simple  shore-line  of  cliffed  headlands  and  filled  bays. 
The  peninsula  of  Sorrento,  on  its  northern  side,  once  resembled 
the  Riviera,  but  it  has  now  been  elevated  fifty  meters,  and  its 
uplifted  bay  plains  have  cliffed  fronts.  The  lower  Tiber,  whose 
mature  valley  floor  is  somewhat  wider  than  its  meander  belt,  is 
consequent  upon  a  volcanic  accident,  for  it  follows  the  trough  be- 
tween the  slopes  of  the  Bracciano  volcanic  center  on  the  north- 
west and  the  Alban  center  on  the  southeast;  farther  upstream,  as 
far  as  Orvieto,  the  river  as  a  rule  follows  a  trough  between  the 
Apennines  and  the  three  volcanic  centers  of  Bolsena,  Vico,  and 
Bracciano.  The  Lepini  mountains  have  along  a  part  of  their  north- 
eastern base  a  young  fault  cliff,  by  which  the  graded  slopes  of  the 
spurs  and  ravines  are  abruptly  cut  off ;  the  fault  cliff  is  easily 
recognized  from  the  train  on  the  line  between  Rome  and  Naples. 
Botanists  and  zoologists  know  very  well  that  a  trained  observer 
can  easily  recognize  and  describe  many  small  items  of  form  that 
pass  without  notice  from  the  untrained  observer.  It  is  the  same 
in  geography,  and  the  only  question  is,  How  can  the  desired 
training  be  secured  ?  Of  the  many  methods  of  geographical 
training  I  believe  that,  as  far  as  the  forms  of  the  land  are  con- 
cerned, no  method  can  equal  the  value  of  one  in  which  explanation 
is  made  an  essential  feature  along  with  observation,  for  there  is 
no  other  in  which  so  many  mental  faculties  are  exercised. 


XIV 

COMPLICATIONS  OF  THE  GEOGRAPHICAL 
CYCLE 

Modern  Geography.  In  earlier  times,  when  it  was  thought  that 
the  past  history  of  the  earth  was  of  a  different  order  from  the 
present,  it  was  natural  enough  that  the  geography  of  the  lands 
should  be  studied  independently  of  geological  methods.  Now  that 
it  has  been  in  more  recent  times  recognized  that  the  yesterdays 
of  geology  closely  resemble  the  to-day  of  geography,  and  that 
the  land  forms  of  the  present  are  the  natural  outcome  of  the  past, 
it  savors  of  an  unnecessary  conservatism  to  hold  to  empirical 
methods  in  geography  instead  of  adopting  the  natural  methods 
of  geology.  The  rational  and  modernized  treatment  of  geograph- 
ical problems  demands  that  land  forms,  like  organic  forms,  shall 
be  studied  in  view  of  their_evolution.  and  that  in  so  far  as  this 
method  of  study  requires,  the  geographer  shall  be  a  geologist.  ^ 

It  is  not  enough,  however,  simply  to  see  that  land  forms  have 
been  evolved  by  the  interaction  of  internal  and  external  agencies, 
—  that  is,  of  forces  that  deform  the  earth's  crust  and  of  forces 
that  carve  its  surface  :  it  must  be  noted  also  that  the  processes 
of  evolution  are  in  the  main  orderly,  and  that  the  evolved  prod- 
ucts are  systematically  related ;  for  however  disorderly  the  action 
of  internal  forces  may  be,  the  forces  that  carve  the  surface  carry 
on  their  work  in  a  regular  fashion  and  thereby  produce  a  system- 
atic sequence  of  surface  forms.  The  forms  that  we  see  are  all 
members  of  this  sequence,  and  are  therefore  fittingly  described 
in  its  terms. 

Ideal  Cycle.  In  the  scheme  of  the  ideal  geographical  cycle  a 
complete  sequence  of  land  forms  of  one  kind  or  another  may  be 
traced  out.  The  cycle  begins  with  crustal  movements  that  place 
a  given  land  mass  in  a  certain  attitude  with  respect  to  base-level. 
The  surface  forms  thus  produced  are  called  initial.  Destructive 
processes  set  to  work  upon  the  initial  forms,  carving  a  whole 

279 


280  PHYSIOGRAPHIC  ESSAYS 

series  of  sequential  forms,  and  finally  reducing  the  surface  to  its 
ultimate  form,  —  a  low  plain  of  imperceptible  relief.  The  sequen- 
tial forms  thus  constitute  a  normal  series  by  which  the  initial 
and  the  ultimate  forms  are  connected.  As  a  result,  the  sequen- 
tial forms  existing  at  any  one  moment  are  so  largely  dependent 
on  the  amount  of  work  that  has  been  done  upon  them  that  they 
are  susceptible  of  systematic  description  in  terms  of  the  stage  of 
the  cycle  which  they  have  reached.  Moreover,  the  correlation 
of  all  the  separate  forms  appropriate  to  any  one  stage  of  the  cycle 
is  so  intimate  and  systematic  that  any  single  form  may  be  des- 
ignated in  an  appropriate  and  consistent  terminology  as  a 
member  of  the  group  of  related  forms  to  which  it  belongs,  and 
thus,  better  than  in  any  other  way,  the  features  of  the  lands  may 
be  systematically  and  effectively  described. 

Geographers  do  not  as  a  rule  recognize  the  correlation  of  forms 
here  referred  to,  and  as  a  result  they  do  not  use  the  principle  of 
correlation  as  an  aid  in  observation  and  description.  This  is  the 
more  to  be  regretted  when,  it  is  noted  that  the  failure  to  take 
advantage  of  the  principle  does  not  arise  from  any  objection  to 
its  correctness,  but  rather  from  inattention  to  it. 

A  statement  of  the  scheme  of  the  cycle  in  its  simplest  form 
was  presented .  before  the  Seventh  International  Geographical 
Congress  at  Berlin  in  1899.  I  desire  here  first  to  consider 
briefly  a  few  objections  that  have  been  urged  against  it,  and 
second  to  set  forth  some  of  the  modifications  by  which  the 
ideally  simple  scheme  may  be  adapted  to  meet  the  complications 
of  nature. 

The  Term  "  Cycled  Objection  has  been  made  by  some  German 
writers  to  the  term  "  cycle,"  because  the  scheme  is  not  concerned 
with  anything  circular.  It  is  a  matter  of  relative  indifference 
what  term  is  used  ;  and  if  any  other  word  would  be  more  gener- 
ally acceptable  than  "  cycle,"  priority  of  usage  of  this  term  and 
whatever  currency  it  has  already  gained  ought  not  to  prevent 
the  adoption  of  its  belated  superior.  In  any  case,  it  is  the  scheme 
and  not  its  name  that  is  important,  and  it  is  a  matter  of  regret 
that  criticism  of  the  latter  should  apparently  detract  from  the 
discussion  or  the  use  of  the  former.  If  the  name  is,  however,  to 
be  seriously  reconsidered,  it  should  be  noted  that  there  is  in  the 


COMPLICATIONS  OF  GEOGRAPHICAL  CYCLE       281 

English  meaning  of  the  word  "  cycle  "  a  sufficient  reason  for  its 
being  used  as  the  name  of  the  scheme  here  considered.  Webster 
defines  it  as  follows  : 

1.  An  imaginary  circle  or  orbit  in  the  heavens. 

2.  An  interval  of  time  in  which  a  certain  succession  of  events  or  phe- 
nomena is  completed,  and  then  returns  again  and  again,  uniformly  and 
continuously  in  the  same  order ;  a  periodical  space  of  time  marked  by  the 
recurrence  of  something  peculiar. 

The  ideal  cycle,  uninterrupted  till  its  end,  and  then  ready  to 
run  its  course  again,  comes  as  near  to  its  dictionary  definition 
as  need  be.  The  actual  and  incomplete  cycles,  of  which  the 
lands  give  so  many  examples,  depart  from  the  ideal  in  the 
various  ways  to  be  considered  below,  and  yet  constantly,  so 
long  as  they  endure,  hold  fast  to  the  essential  features  of  the 
ideal  cycle. 

Some  geographers  have  felt  objection  to  the  term  "  cycle  " 
because  the  first  member  of  the  sequence  of  events  that  it 
includes  is  thought  to  be  unlike  the  last.  As  far  as  plains  and 
plateaus  are  concerned,  this  objection  does  not  hold,  for  they 
begin  and  end  their  ideal  cycle  of  changes  as  low,  featureless 
expanses  ;  and  if  the  views  now  coming  into  vogue  regarding 
certain  mountain  chains  prove  generally  applicable,  as  seems  > 
more  and  more  likely  to  be  the  case,  then  mountains  will  also  as  /  , 
a  rule  have  low-lying  plains  for  their  initial  and  ultimate  forms. 
In  any  event  this  objection  to  the  term  is  based  on  a  subordi- 
nate feature  of  the  scheme  ;  its  greater  feature  of  orderly  prog- 
ress through  a  long  period  of  time,  repeated  with  every  uplift, 
is  the  real  warrant  for  the  name. 

Deductive  Nature  of  the  Cycle.  The  suggestion  has  been  some- 
times made  that  a  scheme  having  a  less  proportion  of  imagined 
or  deduced  elements  and  a  greater  number  of  actual  examples 
would  be  more  generally  acceptable  to  geographers.  In  reply  it 
may  be  said  that  the  scheme  of  the  cycle  is  not  meant  to  include 
any  actual  examples  at  all,  because  it  is  by  intention  a  scheme  of 
the  imagination  and  not  a  matter  of  observation ;  yet  it  should 
be  accompanied,  tested,  and  corrected  by  a  collection  of  actual 
examples  that  match  just  as  many  of  its  elements  as  possible. 
It  may  be  added  that  the  fear  expressed  by  some  that  deduction 


282  .        PHYSIOGRAPHIC  ESSAYS 

here  goes  too  far  is  an  illustration  of  a  feeling  which  comes  from 
adopting  a  very  different  point  of  view  from  that  occupied  by 
those  who  find  profit  in  using  the  scheme  of  the  cycle.  Deduc- 
tion may  go  wrong  if  it  be  illogical,  careless,  or  incomplete,  but 
if  correct  it  cannot  go  too  far.  It  seems  to  me  that  it  would  be 
just  as  appropriate  to  say,  "  In  that  work,  observation  goes  too 
far,"  as  to  say,  "  In  that  scheme,  deduction  goes  too  far."  The 
two  processes  are  entirely  distinct,  and  their  results  should  never 
be  confused.  It  is  as  desirable  to  complete  the  one  as  the  other. 
Each  process  may  supplement  or  reenforce  the  other,  but  neither 
one  can  wholly  replace  the  other,  and  neither  one  should  stop 
until  it  has  covered  the  whole  ground  open  to  its  advance.  From 
the  very  difference  between  observation  and  deduction  as  to 
methods  and  fesults,  it  is  essential  that  any  science  which 
attempts  to  explain  the  seen  by  the  unseen  should  employ  both 
these  mental  processes  as  fully  as  possible.  For  my  own  part,  it 
is  just  as  much  a  desire  to  carry  the  scheme  of  the  cycle  farther 
toward  completion  by  the  free  use  of  accurate  deductive  methods 
as  it  is  to  carry  the  collection  of  actual  facts  farther  toward  com- 
pletion by  the  free  use  of  accurate  observational  methods.  It 
cannot  be  too  strongly  urged  that,  while  the  results  of  the  two 
methods  should  be  carefully  held  apart,  the  two  methods  them- 
selves should  go  hand  in  hand.  Conscious  cultivation  of  each 
method  is  a  most  desirable  preparation  for  physiographic  inves- 
tigation, just  as  it  is  for  physics  or  astronomy,  and  observation 
is  greatly  aided  by  thorough  deduction,  just  as  deduction  is  aided 
by  thorough  observation.  To  object  to  the  scheme  of  the  cycle 
because  it  is  too  deductive  seems  to  me  nothing  less  than  a  mis- 
apprehension as  to  the  logic  of  the  case  —  as  well  object  to  a 
report  on  field  work  because  it  is  too  observational. 

Supposed  Rigidity  of  the  Cycle.  It  has  been  urged  that  the 
scheme  of  the  cycle  is  so  rigid  and  arbitrary  that  it  cannot  be  of 
service  in  describing  the  manifold  phenomena  of  nature.  This 
criticism  is  a  result  of  regarding  the  ideal  cycle  alone,  without 
going  on  to  the  modifications  by  which  it  is  easily  adapted  to 
natural  conditions ;  and  as  this  misconception  may  have  arisen 
either  from  inattention  to  the  more  advanced  view  of  the  scheme, 
or  from  too  great  an  emphasis  on  the  elementary  statement  of 


COMPLICATIONS  OF  GEOGRAPHICAL  CYCLE       283 

the  scheme  in  the  article  above  mentioned,  it  is  all  the  more  de- 
sirable now  to  present  the  scheme  more  fully  and  to  consider  the 
modifications  by  which  it  is  so  easily  made  to  meet  the  compli- 
cated examples  found  in  nature. 

Elementary  Postulates  and  their  Modifications.  The  elemen- 
tary presentation  of  the  ideal  cycle  usually  postulates  a  rapidjoplift 
of  a  land  mass,  followed  by  a  prolonged  stillstand.  The  land  mass 
may  have  any  structure,  but  the  simplest  is  that  of  horizontal 
layers ;  the  uplift  may  be  of  any  kind  and  rate,  but  the  simplest 
is  one  of  uniform  amount  and  rapid  completion  ;  hence  plains 
and  plateaus  have  an  early  place  in  a  systematic  classification  of 
land  forms ;  but  all  sorts  of  structures  and  all  sorts  of  uplifts 
must  be  considered  before  the  scheme  is  completely  worked  out. 
In  my  own  treatment  of  the  problem  the  postulate  of  rapid  uplift 
is  largely  a  matter  of  convenience,  in  order  to  gain  ready  entrance 
to  the  consideration  of  sequential  processes  and  of  the  successive 
stages  of  development,  — young,  mature,  and  old,  —  in  terms  of 
which  it  is  afterwards  so  easy  to  describe  typical  examples  of 
land  forms.  Instead  of  rapid  uplift^gradual  uplift  may  be  postu- 
lated with  equal  fairness  to  the  scheme,  but  with  less  satisfac- 
tion to  the  student  who  is  then  first  learning  it ;  forjjradual 
^uplift  requires  the  consideration  of  erosion  during  uplift.  It  is 
therefore  preferable  to  speak  of  rapid  uplift  in  the  first  presen- 
tation of  the  problem,  and  afterwards  to  modify  this  elementary 
and  temporary  view  by  a  nearer  approach  to  the  probable  truth ; 
and  this  has  been  for  some  years  past  my  habitual  method  in 
teaching. 

A  special  case  necessitating  explanation  by  slow  uplift  maybe 
easily  imagined.  If  an  even  upland  of  resistant  rocks  be  inter- 
rupted by  broadly  open  valleys,  whose  gently  sloping,  evenly 
graded  sides  descend  to  the  stream  banks,  leaving  no  room  for 
flood  plains,  it  would  suggest  slow  uplift ;  the  absence  of  flood 
plains  would  show  that  the  streams  have  not  yet  ceased  deepen- 
ing their  valleys,  and  the  graded  valley  sides  would  show  that 
the  downward  corrasion  by  the  streams  has  not  been  so  rapid 
that  the  relatively  slow  processes  of  slope  grading  could  not  keep 
pace  with  it.  In  such  a  case  there  would  have  been  no  early 
stage  of  dissection  in  which  the  streams  were  inclosed  in  narrow 


284  PHYSIOGRAPHIC  ESSAYS 

valleys  with  steep  and  rocky  walls ;  the  stage  of  youth  would 
have  been  elided  and  that  of  maturity  would  have  prevailed  from 
the  beginning,  but  with  constantly  increasing  relief  as  long  as 
uplift  continued.  Examples  of  this  kind  must  be  rare ;  it  is 
nearly  always  the  case  that  a  beginning  of  flood-plain  develop- 
ment is  made  before  the  valley  sides  are  completely  graded  to 
even,  waste-covered  slopes ;  and  hence  the  usual  supposition  of 
rapid  uplift  —  rapid  as  the  earth  views  time  —  is  probably  essen- 
tially correct.  Moreover,  it  should  not  be  forgotten  that  uplift 
must  usually  be  much  faster  than  the  downwear  of  general  sub- 
aerial  erosion,  however  nearly  it  may  be  equaled  by  the  corrasion 
of  large  rivers.  The  original  postulate  of  rapid  uplift  therefore 
requires  only  a  moderate  amount  of  modification  to  bring  it  into 
accord  with  most  of  the  land  forms  that  we  have  to  consider. 

The  postulate  of  a  stillstanding  land,  unmoved  until  it  is  worn 
down  to  a  plain,  is  like  the  postulate  of  rapid  uplift,  a  matter  of 
convenience  for  first  presentation  ;  but  it  is  also  something  more. 
It  is  essential  to  the  analysis  of  the  complete  scheme  because 
only  in  the  ideal  case  of  a  land  mass  that  stands  still  after  its 
uplift  can  one  trace  out  the -normal  series  of  sequential  events  in 
which  the  real  value  of  the  cycle  scheme  consists,  and  thus  learn 
the  systematic  correlation  of  forms  that  characterizes  each  stage 
of  the  cycle.  It  is  only  after  the  normal  series  has  been  analyzed 
that  the  peculiar  combinations  of  forms  which  result  from  two 
or  more  cycles  of  erosion  can  be  understood.  The  recognition  of 
the  systematic  correlation  of  individual  forms  appropriate  to  any 
given  stage  of  the  cycle  constitutes  a  marked  advance  over  that 
earlier  stage  of  physical  geography  in  which  the  various  elements 
of  form  were  described  as  if  they  had  nothing  to  do  with  one 
another.  One  of  the  most  notable  features  of  this  advance  is 
the  great  increase  in  the  interest  that  attaches  to  the  study.  The 
increase  of  interest  is,  however,  a  most  natural  result  of  the 
newer  method,  for  interest  is  always  aroused  by  closer  approach 
to  the  true  nature  of  things  and  by  the  perception  that  what  had 
been  mistaken  for  meaningless,  inert  forms  are  in  reality  actively 
engaged  in  a  great  series  of  meaningful  changes.  The  marvelous 
interdependence  of  the  various  parts  of  a  maturely  organized 
drainage  system  must,  indeed,  when  fully  apprehended,  awaken 


COMPLICATIONS  OF  GEOGRAPHICAL  CYCLE        285 

wonder  as  well  as  interest ;  but  it  is  only  under  the  supposition 
of  an  essentially  stillstanding  land  that  the  mature  organization 
of  drainage  systems  can  be  reached.  Hence,  however  improbable 
a  prolonged  stillstand  of  a  land  mass  may  seem,  the  consequences 
of  such  a  condition  should  be  followed  out  with  care  as  furnish- 
ing the  norm  of  the  scheme,  and  hence  as  forming  the  essential 
introduction  to  all  manner  of  complications  that  follow.  Only 
after  the  norm  has  been  established  can  the  effects  of  various 
movements  —  uplift,  depression,  warping,  breaking  —  be  duly 
considered. 

Interruptions  of  the  Cycle.  Movements  of  the  land  mass  may 
evidently  occur  at  any  stage  in  the  advance  of  the  cycle.  They 
then  interrupt  the  further  progress  of  sculpturing  processes  with 
respect  to  the  former  base-level  by  placing  the  land  mass  in  a 
new  attitude  as  referred  to  the  sea.  The  previous  cycle  is  thus 
cut  short  and  a  new  cycle  is  entered  upon.  Such  movements  are 
given  the  semi-technical  name  of  interruptions,  and  the  partial 
cycles  thus  separated  are  by  ellipsis  spoken  of  simply  as  cycles. 
The  effects  of  interruption  are  chiefly  observable  in  cases  where 
the  newly  opened  cycle  has  reached  a  less  advanced  stage  than 
that  of  the  previous  cycle  at  the  time  of  the  interruption,  —  as, 
for  example,  in  western  Germany,  where  the  young  or  sub-mature 
valley  of  the  Rhine  is  carved  in  the  old  torso  or  peneplain  of  the 
Schiefergebirge  ;  or  in  western  Pennsylvania,  where  the  sub-ma- 
ture valley  of  the  Monongahela  is  incised  in  the  floor  of  an  older  \  \j 
valley  in  the  much-dissected  Allegheny  plateau.  If  the  opposite 
relation  obtains,  the  more  advanced  work  of  the  new  cycle  will  j 
obliterate  the  less  advanced  work  of  the  previous  cycle.  It  is  in  ' 
connection  with  interruptions  that  such  terms  as  " revived,"  "re- 
juvenated," and  "  drowned  "  have  come  into  use ;  they  are  so  con- 
venient that,  once  adopted,  they  are  not  likely  to  be  given  up. 
Certain  it  is  that  the  conception  of  cycles  and  interruptions  has 
been  extremely  fertile  ;  it  has  led  to  the  recognition  and  ready 
description  of  features  that  previously  passed  unnoticed,  as  in 
the  case  of  the  Pennsylvania  Appalachians. 

Interruptions  due  to  simple  uplift  or  depression  have  been  most 
commonly  considered,  but  tilting  has  been  shown  by  Campbell 
to  have  appropriate  consequences  in  drainage  modifications  in 


286  PHYSIOGRAPHIC  ESSAYS 

the  eastern  United  States ;  the  discussion  of  block  faulting  has 
been  opened  by  Gilbert  and  Russell  for  the  Great  Basin  region 
of  Utah  and  Nevada ;  folding  has  been  considered  for  the  Alps, 
the  Jura,  and  the  Appalachians,  and  if  the  Jura  mountains  must 
now  be  withdrawn  from  the  class  of  a  one-cycle  folded  range, 
they  will  only  join  the  majority  as  an  example  of  a  region  of 
disordered  structure  once  worn  down  and  now  broadly  uplifted 
and  maturely  dissected  in  a  second  cycle  of  erosion. 

Certain  it  is  that  when  various  kinds  and  degrees  of  interrup- 
tion at  various  stages  in  a  cycle  have  been  considered,  the  variety 
of  possible  combinations  becomes  so  great  that  there  is  no  diffi- 
culty whatever  in  matching  the  variety  of  nature.  The  difficulty 
is' indeed  reversed  ;  there  are  not  enough  kinds  of  observed  facts 
on  the  small  earth  in  the  momentary  present  to  match  the  long 
list  of  deduced  elements  of  the  scheme.  A  notable  example  of 
the  deficiency  of  observation  may  be  pointed  out  in  connection 
with  belted  coastal  plains.  A  number  of  examples  are  known  in 
which  the  upland  belt  or  cuesta  is  separated  from  the  oldland  by 
a  continuous  inner  lowland,  with  appropriate  drainage  by  longi- 
tudinal subsequent  streams,  diverted  consequent  headwaters, 
short  obsequents  running  down  the  infacing  slope  of  the  cuesta, 
and  beheaded  consequents  on  the  outlooking  slope.  The  elastic 
scheme  of  the  cycle  easily  matches  these  facts  of  observation, 
but  there  are  no  known  examples  of  belted  plains  in  earlier 
stages  to  match  the  several  deduced  phases  of  cuesta  develop- 
ment which  are  familiarly  included  in  the  scheme  of  the  cycle. 
Rigidity  and  deficient  variety  can  therefore  hardly  be  regarded 
as  defects  of  the  elaborated  scheme  of  the  geographical  cycles. 

Educational  Value  of  the  Elaborated  Scheme.  It  is  perhaps 
true  that  those  who  have  already  formed  habits  of  study  which 
do  not  include  the  apparently  overlong  deductive  consideration 
of  a  scheme  for  the  treatment  of  land  forms  may  become  impatient 
at  what  they  regard  as  a  too  elaborative  series  of  unpractical  ab- 
stractions, and  that  they  may  prefer  to  treat  each  actual  case  in 
such  a  way  as  seems  appropriate  when  the  case  arises,  and  thus 
allow  a  scheme  of  treatment  to  grow  in  the  irregular  order  of 
accidental  accumulation  rather  than  in  the  more  systematic  order 
of  deductive  development.  But,  on  the  other  hand,  those  who 


COMPLICATIONS  OF  GEOGRAPHICAL  CYCLE       287 

are  now  forming  their  habits  of  study  gain  great  advantage  from 
the  more  thorough  consideration  that  the  scheme  of  the  cycle 
gives  as  compared  with  the  less  systematic  methods  of  treatment. 
Beginners  thus  take  up  the  study  of  land  forms  in  their  natural, 
genetic  relations,  and  discover  a  fullness  and  continuity  and 
reasonableness  of  meaning  where  explanation  would  otherwise 
be  fragmentary  or  wanting.  Moreover,  even  the  preliminary  pres- 
entation of  the  ideal  cycle  need  not  be  wholly  deductive  or 
abstract ;  it  may  be  enlivened  by  the  frequent  introduction  of 
actually  observed  examples  which  confirm  its  deductions  at  every 
stage  of  progress  ;  the  method  of  presentation  may  be  at  any 
time  changed  from  deductive  to  inductive,  and  a  group  of  ob- 
served facts  for  which  the  scheme  as  then  developed  has  no 
match  may  be  empirically  described  as  a  means  of  exciting  the 
further  extension  of  the  scheme.  The  only  essential  is  that  not 
merely  the  rigid  ideal  conception  of  a  single  cycle,  but  many 
combinations  of  interrupted  cycles,  should  be  familiarized  by  dis- 
cussion and  illustration  until  they  are  easily  carried  in  the  mind ; 
for,  as  in  the  case  of  the  Greek  alphabet,  of  musical  notation,  or 
of  contoured  maps,  so  in  the  case  of  the  cycle,  it  is  only  to  those 
who  reach  the  point  of  facility  in  using  its  complications  that  the 
scheme  becomes  of  practical  service  in  physiographic  work. 

Verity  of  the  Cycle.  Although  it  is  thus  shown  that  the  com- 
plications arising  from  interruptions  are  of  great  practical  impor- 
tance, it  is  not  true  that  the  ideal  cycle  is  only  an  abstraction. 
It  is  true  that  the  consideration  of  actual  examples  frequently 
shows  repeated  earth  movements  or  interruptions  which  result 
in  a  succession  of  partial  cycles,  some  of  which  may  be  so  short 
as  to  be  merely  brief  episodes  in  an  otherwise  long  history.  It 
must  not,  however,  be  forgotten  that  cycles  of  erosion  have  in 
some  cases  reached  at  least  the  penultimate  stage,  without  sig- 
nificant interruption,  for  the  explanation  of  certain  uplands  as 
now  uplifted  and  partly  dissected  peneplains  is  supported  by  a 
large  array  of  strong  evidence.  However  many  interruptions  the 
earlier  history  of  such  districts  may  have  witnessed,  a  long  cycle 
of  untroubled  calm  seems  afterwards  to  have  settled  upon  them, 
in  whose  advanced  progress  all  traces  of  previous  cycles  have 
been  obliterated.  However  rare  it  may  be  to  find  peneplains  still 


288  PHYSIOGRAPHIC  ESSAYS 

holding  to-day  the  attitude  with  respect  to  base-level  that  they 
must  have  held  while  they  were  slowly  worn  down,  the  facts  of 
observation  on  partly  dissected  uplands  find  no  explanation  save 
that  which  carries  them  all  uninterruptedly  through  the  stages 
of  short  youth  and  longer  maturity  far  into  very  long  old  age. 
Thus  in  these  cases  at  least  there  is  full  warrant  for  the  original 
postulate  of  a  stillstanding  land  mass.  The  verity  of  low-lying 
undissected  peneplains  to-day,  and  the  reasonable  inference  of 
their  more  common  occurrence  in  the  past,  belong  with  historical 
geology,  where  they  are  destined  to  play  an  important  part  in 
terrestrial  physics,  along  with  such  matters  as  marine  trans- 
gressions of  widespread  occurrence,  like  that  of  the  Cambrian 
and  Cretaceous  seas. 

Normal  and  Special  Agencies.  Thus  far  it  has  been  tacitly 
implied  that  land  sculpture  is  effected  by  the  familiar  processes 
of  rain  and  rivers,  of  weather  and  water.  It  is  certainly  true  that 
the  greater  part  of  the  land  surface  has  been  carved  by  these 
agencies,  which  may  therefore  be  called  the  prevailing  or  normal 
agencies ;  but  it  is  important  to  consider  the  peculiar  work  of 
other  special  agencies,  namely  ice  and  wind.  It  is  not  to  be 
implied  that  any  special  agency  ever  works  alone,  but  that  it 
dominates  in  its  time  and  place,  as  ice  does  in  Greenland,  as 
wind  does  in  certain  deserts,  and  as  the  rain  and  rivers  do  in 
better-favored  lands  ;  it  is  indeed  important  to  recognize  that  the 
various  agencies  work  to  a  certain  extent  in  combination,  for 
frosty  weathering  and  the  active  washing  of  rainy  thaws  on  the 
higher  peaks  and  ridges  is  a  characteristic  accompaniment  of 
glacial  erosion  in  mountain  regions ;  and  even  in  deserts  occa- 
sional cloudbursts  may  provide  short-lived  but  strenuous  streams 
that  develop  and  maintain  valley  systems,  with  their  well-organ- 
ized downhill  lines,  in  defiance  of  the  ^prevalent  winds,  which 
could  never  alone  produce  any  such  system  of  coordinated  and 
ramifying  slopes.  It  is  only  recently  that  the  conception  of  a 
whole  cycle  of  glacial  erosion  has  been  discussed,  and  a  whole 
cycle  of  wind  erosion  is  as  yet  a  relatively  neglected  consider- 
ation ;  yet  it  cannot  be  doubted  that  both  of  these  special  ideal 
cycles  deserve  deliberate  analysis,  for  until  such  analysis  is  made 
the  next  step,  and  one  of  more  frequent  application,  cannot  be 


COMPLICATIONS  OF  GEOGRAPHICAL  CYCLE        289 

safely  taken,  namely,  the  combination  in  a  single  cycle,  uninter- 
rupted by  land  movements,  of  a  succession  of  normal  and  special 
agencies.  Thus  we  come  to  the  important  complication  of  cli- 
matic changes. 

Normal  and  Accidental  Climatic  Changes.  The  normal  ideal 
cycle  postulates  no  climatic  change  except  such  as  accompanies 
the  decrease  of  surface  temperatures  and  the  increase  of  pre- 
cipitation caused  by  the  initial  (relatively)  rapid  uplift,  and  the 
gradual  rise  of  surface  temperatures  and  decrease  of  precipita- 
tion that  accompanies  the  slow  wearing  down  of  the  region  to  a 
lowland  plain.  That  such  climatic  changes  have  taken  place 
seems  fanciful  at  first,  but  more  deliberate  consideration  must 
change  the  fancy  into  matter  of  fact.  It  was  a  wild  flight  of  the 
scientific  imagination  by  which  Tyndall  was  led  to  the  brilliant 
suggestion  that  Alpine  glaciation  had  decreased  because  the 
glaciers  had  worn  the  Alps  down.  The  famous  physicist  mistook 
a  short-lived  climatic  accident  for  a  large  part  of  a  cycle.  Yet  it 
cannot  be  doubted  that  many  mountain  ranges  of  earlier  geologi- 
cal times  have  been  worn  down  in  some  way  or  other,  and  that 
the  climate  of  their  region  has  experienced  changes  appropriate 
to  such  changes  in  the  topography.  The  distribution  and  indeed 
the  specific  modification  of  land  plants  and  land  animals  must 
have  repeatedly  been  influenced  by  such  changes  in  land  forms, 
for  while  short  climatic  accidents,  like  the  several  glacial  epochs 
of  post-Tertiary  time,  were  rapid  enough  to  cause  migration  or 
extinction  of  organic  forms,  the  vastly  slower  change  of  climate 
normal  to  the  ideal  cycle  may  only  provoke  adaptations  to  new 
conditions. 

It  thus  appears  that  climatic  changes  of  the  kind  that  have 
been  most  discussed  in  geographical  literature  are  independent 
of  the  ideal  cycle.  Whether  they  are  marked  by  changes  from 
non-glacial  to  glacial,  or  from  sub-arid  to  arid  conditions,  they 
occur  at  any  stage  of  a  cycle,  and  are  therefore  noted  by  the 
semi-technical  term  "  accidents."  The  delicate  shore -lines  of 
lake  Bonneville  on  the  elaborately  carved  slopes  of  the  Wasatch 
mountain  block  in  Utah,  or  the  relatively  small  terminal  moraine 
that  crosses  the  Cretaceous  sky  lines,  the  Tertiary  slopes  and 
valley  floors,  and  the  post-Tertiary  trenches  in  the  Pennsylvania 


2QO  PHYSIOGRAPHIC  ESSAYS 

Appalachians,  suffice  to  show  how  brief  climatic  accidents  are  in 
comparison  with  the  cycles  of  erosion  that  wear  down  mountains. 

Volcanic  Accidents.  Volcanic  eruptions  are  accidents  of  an- 
other kind.  They  occur  at  any  stage  of  a  cycle  and  at  any  part 
of  a  surface,  entirely  irrelevant  to  the  normal  development  and 
distribution  of  surface  culture.  They  may  reach  so  large  a  scale 
as  to  deserve  the  name  of  revolutions,  as  in  Oregon  or  western 
India,  but  when  of  smaller  dimensions,  as  in  central  France,  the 
haphazard  or  accidental  manner  in  which  they  interfere  with  the 
orderly  sequence  of  normal  processes  is  well  illustrated. 

The  Cycle  of  the  Shore-Line.  There  is  still  to  be  considered 
the  work  of  the  ocean  on  the  shore-line  of  the  lands ;  but  here, 
as  before,  the  scheme  includes  an  initial  stage,  when  a  movement 
of  the  earth's  crust  gives  a  new  position  to  the  shore -line,  and  a 
systematic  series  of  normal  sequential  changes  to  an  ultimate 
stage,  in  which  all  the  land  is  worn  away.  This  embraces  all  the 
possibilities  of  the  ideal  case.  Like  the  processes  of  surface 
carving,  the  processes  of  shore-line  development  are  subject  to 
variation  with  climate,  from  the  work  of  the  ice  foot  in  polar 
regions  to  the  work  of  coral  reefs  and  mangrove  swamps  in  the 
torrid  zone. 

One  significant  peculiarity  of  the  development  of  the  shore- 
line is  its  immediate  recognition  of  changes  of  level  or  interrup- 
tions ;  not  only  changes  in  the  local  land  mass,  in  which  case  the 
change  is  shown  in  its  full  measure,  but  in  any  part  of  the  sea- 
bottom  or  sea-border,  in  which  case  every  seashore  line  is  also 
affected  in  some  degree.  This  contrast  leads  to  the  inference 
that  the  product  of  long-continued  work  of  the  shore-line  forces 
on  a  fixed  level  or  on  a  uniformly  changing  level  is  less  likely  to 
be  found  than  the  product  of  long-continued  work  in  an  inland 
region,  where  a  series  of  small  and  frequent  interruptions  (eleva- 
tions and  depressions)  might  hardly  make  themselves  felt.  The 
contrast  is  still  more  marked  between  the  sensitive  and  fluctuat- 
ing shore-line  and  the  relatively  fixed  local  base-level  of  a  large 
interior  drainage  basin,  which  knows  nothing  of  elevations  and 
depressions  except  in  the  climatic  variations  they  may  cause, 
and  which  is  subject  to  significant  change  only  by  warping  or 
by  the  development  of  a  drainage  outlet  to  the  sea.  A  case  of 


COMPLICATIONS  OF  GEOGRAPHICAL  CYCLE       291 

the  latter  kind  seems  now  to  be  in  progress  where  the  upper 
branches  of  Indian  rivers  are  gnawing  headward  through  the 
Himalayas  and  giving  discharge  to  previously  inclosed  Tibetan 
basins. 

The  sensitiveness  of  a  local  shore -line  to  changes  in  the  ocean 
basin  or  border  all  around  the  world  makes  extensive  plains  of 
marine  abrasion  of  improbable  occurrence ;  but  the  chief  reason 
for  interpreting  as  sub-aerial  peneplains  those  areas  that  were 
formerly  explained  as  the  work  of  the  seashore  waves  is  that  the 
unconsumed  residual  mountains,  by  which  peneplains  are  so  often 
adjoined,  have  no  appearance  of  a  sea  cliff  along  their  border, 
and  have  every  appearance  of  the  frayed-out  base-line  that  sub- 
aerial  erosion  would  necessarily  produce.  This  is  admirably 
shown  along  the  inner  border  of  the  Piedmont  peneplain  in 
North  Carolina  and  Georgia,  where  the  residual  mountains  of 
the  southern  Appalachians  give  forth  rambling,  sprawling  spurs, 
that  interlock  with  wide-open,  flat-floored,  ramifying  valleys. 
Mighty  as  are  the  destructive  processes  of  the  shore -line,  they 
seem  to  have  been  too  seldom  allowed  continued  effort  at  a 
given  level  long  enough  to  accomplish  the  great  work  of  which 
they  are  undoubtedly  capable.  Richter  was  right  in  calling  the 
coast  plain  of  Norway,  first  explained  by  Reusch,  the  greatest 
single  piece  of  shore-line  work  of  which  we  as  yet  have  definite 
knowledge. 

Passive  Masses,  Active  Agencies,  Creeping  Waste.  The  fully 
developed  .scheme  of  the  cycle  recognizes  the  passive  mass  of 
the  earth  crust,  raised  here  and  there,  and  thus  exposed  to  the 
destructive  processes  ;  the  various  destructive  processes  or  agen- 
cies by  which  the  passive  crustal  mass  is  systematically  carved  ; 
and  the  waste  or  "  chips  "  that  result  from  the  carving  processes. 
The  waste  is  much  less  active  in  its  creeping  and  washing  move- 
ments than  are  rivers,  glaciers,  or  winds  in  their  flow,  and  yet 
the  waste  is  much  more  active  in  its  down-slope  movements  than 
is  the  passive  mass  on  which  it  rests.  The  cloak  of  creeping 
rock  waste  that  covers  a  graded  hillside  is  as  much  deserving  of 
systematic  description  as  is  the  great  rock  mass  of  the  hill  as  a 
whole,  or  the  slender  thread  of  the  stream  in  the  valley ;  and  the 
suggestive  correlations  that  result  from  giving  a  definite  place 


292  PHYSIOGRAPHIC  ESSAYS 

in  systematic  physiography  to  the  "  forms  assumed  by  the  waste 
of  the  land  on  the  way  to  the  sea  "  are  sufficient  warrant  for  this 
element  of  the  scheme. 

Terminology  of  the  Cycle.    It  thus  appears  that  the  scheme 

*-©f  the  simple  ideal  cycle  may  be  gradually  and  systematically 

modified  until  its  deductions  cover  all  manner  of   structures, 

agencies,  waste  forms,  interruptions,  and  accidents.  ^When  thus 

conceived  it  is  a  powerful  instrument  of  research,  an  invaluable 

equipment  for  the  explorer.    It  is  not  arbitrary  or  rigid,  but 

J  elastic  and  adaptable.    It  is  a  compendium  of  all  the  pertinent 

results  of  previous  investigations. 

A  very  natural  accompaniment  of  the  systematic  development 
and  elaboration  of  the  scheme,  along  with  the  general  advance 
of  geology  and  geography,  has  been  the  introduction  of  a  cer- 
tain number  of  terms  with  which  to  name  certain  ideas  as  well  as 
certain  land  forms  of  special  importance.  Cycle,  stage  ;  initial, 
sequential,  ultimate  ;  young,  mature,  old  ;  interruption,  accident ; 
consequent,  grade,  adjustment,  revived,  drowned,  and  so  on,  are 
examples  of  ordinary  nouns  and  .adjectives  thus  used  in  a  more 
or  less  new  and  special  sense.  The  extension  of  the  meaning  of 
some  of  these  words  beyond  their  ordinary  definitions  is  perfectly 
in  accord  with  the  normal  growth  of  languages  as  an  accompani- 
ment to  the  growth  of  experience.  "  The  ordinary  processes  by 
which  words  change  their  meanings  are,  then,  essentially  the  same 
as  the  devices  of  poetry  ;  or,  to  express  the  fact  more  accurately, 
the  figurative  language  of  poetry  differs  from  the  speech  of  com- 
mon life  mainly  in  employing  fresher  figures,  or  in  revivifying 
those  which  have  lost  their  freshness  from  age  and  constant 
use.  Language  is  fossilized  poetry  which  is  constantly  being 
worked  over  for  the  uses  of  speech.  Our  commonest  words 
are  worn-out  metaphors." 

Other  terms  are  new-made,  in  the  absence  of  any  satisfactory 
existing  words.  Such  are  base-level,  peneplain,  obsequent,  inse- 
quent,  and  a  very  few  more.  It  is  curious  to  note  the  disturb- 
ance that  these  few  words  have  occasioned.  Some  go  so  far  as 
to  say  that  every  new  term  is  a  positive  detriment  to  science,  as 
if  it  were  possible  to  hold  the  new  wine  of  discovery  in  the  old 
bottles  of  ignorance.  Others  complain  that  they  find  it  difficult 


COMPLICATIONS  OF  GEOGRAPHICAL  CYCLE        293 

to  remember  the  different  meanings  of  similar  terms,  such  as 
subsequent  and  resequent,  consequent  and  obsequent ;  but 
so  far  as  I  have  looked  into  this  difficulty,  it  is  based  on  un- 
familiarity  with  the  ideas  here  concerned  rather  than  with  the 
words  by  which  the  ideas  are  named,  and  the  sufficient  cure 
for  the  difficulty  is  to  give  a  more  serious  and  sustained  atten- 
tion to  the^ubject  in  which  the  terms  are  employed.  Even  so 
serviceable  a  term  as  "  monadnock  "  has  been  objected  to  be- 
cause it  is  not  English ;  and  yet  the  objector  may  complacently 
accept  meander  and  atoll  and  a  host  of  other  foreigners  without 
noting  that  they  may  have  once  seemed  as  strange  and  bar- 
barous to  his  predecessors  as  monadnock  now  seems  to  him. 
"  Islandmountain,"  literally  translated  from  the  term  which  Ger- 
man physiographers  use  for  "  monadnock,"  is  not  likely  to  be 
acceptable  in  English  usage.  Peneplain  has  been  unjustly  con- 
demned as  a  badly  formed  hybrid,  apparently  on  the  ground  that 
the  Latin  "pene"  and  the  English  "plain"  ought  not  to  be  joined; 
yet  this  word  was  approved  by  expert  philologists  before  it  was 
announced,  and  it  has  a  host  of  accepted  analogues.  If  we  hap- 
pen to  have  kept  the  root  in  its  Latin  form  in  peninsula,  we  have 
not  in  promontory;  peneplain  is  just  as  good  as  penult  or  prom- 
ontory, in  both  of  which  the  root  is  given  in  Anglicized  form, 
while  the  Latin  form  of  the  prefix  is  kept  unchanged. 

With  regard  to  all  this  matter  of  terminology,  I  allow  myself 
here  the  pleasure  of  reciting  a  personal  incident.  An  experienced 
geographer  expressed  to  me  on  a  certain  occasion  about  ten  years 
ago  his  regret  that  so  many  new  and  unnecessary  terms  had  been 
introduced  into  the  study  of  physiography.  I  replied  that  the 
terms  did  not  seem  to  me  unnecessary  or  unduly  numerous. 
Some  months  later  my  friend  wrote  that  he  had  looked  more 
fully  into  the  matter,  and  added  : 

It  gives  me  pleasure  to  tell  you  that  I  now  fully  value  the  use  of  the  exact 
terminology  .  .  .  and  I  beg  of  you  kindly  to  excuse  the  remarks  which  I 
was  too  prompt  to  make*.  .  .  against  the  introduction  of  new  terms. 

Relation  of  Geology  and  Geography.  Some  have  urged  that 
the  scheme  of  the  cycle  is  nothing  more  than  a  part  of  physical 
geology,  and  have  thereby  thought  to  criticise  the  scheme 


294  PHYSIOGRAPHIC  ESSAYS 

unfavorably.  They  are  essentially  right  as  to  the  geological 
quality  of  the  scheme,  but  this  is,  to  my  mind,  a  high  merit. 
Yet,  although  largely  geological,  the  scheme  of  the  cycle  is  at 
once  something  less  and  something  more  than  physical  geology. 
It  is  avowedly  and  necessarily  geological  in  the  sense  stated  at 
the  beginning  of  this  essay,  because  the  time  is  now  passed 
when  the  existing  forms  of  the  land  can  be  considered  apart 
from'  those  of  the  past  or  apart  from  the  processes  and  the 
changes  that  have  accompanied  the  past  into  the  present  on 
the  way  to  the  future.  It  is  an  obsolescent  system  of  the 
sciences  that  would  set  geography  apart  from  geology,  and  it 
is  a  confused  system  that  fails  to  recognize  the  relations  and 
distinctions  between  the  two.  Geology  is  in  fact  made  up  of 
a  countless  number  of  geographies,  horizontally  stratified  in 
relation  to  the  vertical  time  line ;  geography  is,  therefore,  only 
one  day's  issue  of  the  world  journal  whose  complete  file  con- 
stitutes geology.  Geology  is,  moreover,  particularly  concerned 
with  changes  recorded  in  the  order  of  their  time  sequence,  — 
that  is,  with  the  historical  element  of  earth  science ;  geography 
is  concerned  chiefly  with  momentary  views,  and  has,  therefore, 
to  do  with  the  distribution  of  phenomena  over  the  earth's  sur- 
face at  one  time  rather  than  with  phenomena  in  their  order  of 
occurrence  through  the  passing  ages.  Every  epoch  or  moment 
of  the  past  has  had  its  own  geography ;  if  we  associate  this  name 
chiefly  with  the  present,  it  is  not  so  much  because  the  geography 
of  the  present  is  inherently  more  important  than  the  geographies 
of  earlier  times  as  because  it  is  existent  and  visible. 

The  scheme  of  the  cycle,  by  which  land  forms  may  be 
described,  is,  therefore,  properly  of  a  geological  nature.  It  is, 
however,  less  than  physical  geology  in  that  it  does  not  study 
phenomena  in  their  time  sequence  for  the  purpose  of  learning 
the  history  through  which  they  have  passed,  but  for  the  pur- 
pose of  using  this  history  in  order  to  describe  their  present 
state.  The  geographer  employs  as  much  of  geological  methods 
as  serves  his  needs  in  giving  accurate  statement  of  his  facts  ; 
yet  he  remains  a  geographer.  In  the  same  way  the  chemist 
employs  physical  methods  in  weighing  his  precipitates,  yet  he 
remains  a  chemist. 


COMPLICATIONS  OF  GEOGRAPHICAL  CYCLE        295 

The  scheme  of  the  cycle  is  more  than  physical  geology  in 
that  it  attaches  great  importance  to  form  as  the  product  of 
process,  and  to  the  systematic  correlation  of  normally  asso- 
ciated forms,  while  physical  geology,  as  ordinarily  treated,  is 
largely  contented  with  the  more  independent  and  local  study 
of  process  and  product.  It  is  obvious,  however,  that  the  scheme 
of  the  cycle  may  be  used  interchangeably  as  a  means  of  geo- 
logical investigation  or  as  a  means  of  physiographic  description. 
The  upland  of  southern  New  England  may,  on  the  one  hand, 
be  described  as  an  uplifted  and  maturely  dissected  peneplain; 
or,  on  the  other  hand,  through  the  forms  thus  described,  de- 
termination may  be  made  of  a  regional  uplift  that  might  other- 
wise elude  recognition. 

Practical  Value  of  the  Cycle.  The  elaborated  scheme  of  the 
cycle  provides  a  systematic,  rational,  genetic  classification  for 
land  forms ;  the  possession  of  such  a  classification  promotes 
the  collection  and  the  description  of  observable  facts ;  the 
understanding  of  the  classification  greatly  assists  the  trained 
reader  in  appreciating  the  descriptions  of  the  trained  explorer. 


XV 

THE  GEOGRAPHICAL  CYCLE  IN  AN  ARID 
CLIMATE 

Normal  and  Special  Cycles.  The  scheme  of  the  geographical 
cycle  is  usually  developed  with  respect  to  a  land  surface  under 
ordinary  climatic  conditions,  not  so  dry  but  that  all  parts  of  the 
surface  have  continuous  drainage  to  the  sea,  nor  so  cold  but  that 
the  snow  of  winter  all  disappears  in  summer.  The  term  "  normal 
climate"  has  been  applied  to  such  conditions,  and  "normal  cycle" 
to  the  scheme  that  embodies  them.  It  is  chiefly  this  scheme 
that  I  have  elsewhere  treated  on  various  occasions  (#,  &,  c,  //). 

The  general  scheme  of  the  geographical  cycle  needs  adapta- 
tion to  two  special  climates  :  one,  glacial ;  the  other,  arid.  The 
glacial  cycle  received  brief  attention  in  my  essay  on  "  Glacial 
Erosion  in  France,  Switzerland,  and  Norway,"  but  now  needs 
supplement  in  view  of  the  later  studies  by  Richter,  de  Martonne, 
Lawson,  and  others,  as  to  the  forms  of  glaciated  mountains,  and 
in  view  of  the  theory  announced  by  Gilbert  that  glaciers  are  not 
buoyed  up  while  they  rest  on  the  sea-bottom,  and  that  they  may 
therefore  erode  their  channels  deep  below  sea-level.  The  arid 
cycle  has  not  been  considered  as  a  whole,  although  special  studies 
of  desert  conditions  have  been  made  by  various  observers,  notably 
by  Walther.  The  following  general  considerations  are  based  on 
the  work  of  others  as  well  as  on  my  own  observations  in  the  arid 
regions  of  the  western  United  States  and  of  western  Asia ;  they 
are  presented  for  the  most  part  in  an  intentionally  and  avowedly 
deductive  manner,  but  they  are  checked  by  facts  from  stage  to 
stage.  My  especial  indebtedness  to  Passarge  is  stated  below. 

The  Arid  Climate.  The  essential  features  of  the  arid  climate, 
as  it  is  here  considered,  are  :  so  small  a  rainfall  that  plant  growth 
is  scanty,  that  no  basins  of  initial  deformation  are  filled  to  over- 
flowing, that  no  large  trunk  rivers  are  formed,  and  hence  that 
the  drainage  does  not  reach  the  sea. 

296 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE      297 

The  agencies  of  sculpture  and  their  opportunities  for  work  in 
arid  regions  are  peculiar  in  several  respects.  The  small  rainfall 
and  the  dry  air  reduce  the  ground  water  to  a  minimum.  In  its 
absence,  weathering  is  almost  limited  to  the  surface,  and  is  more 
largely,  physical  than  chemical.  The  streams  are  usually  shorter 
than  the  slopes,  and  act  as  discontinuously  at  their  lower  as  at 
their  upper  ends.  The  scarcity  of  plant  growth  leaves  the  surface 
relatively  free  to  the  attack  of  the  winds  and  of  the  intermittent 
waters.  Hence,  in  the  production  of  fine  waste,  the  splitting, 
flaking,  and  splintering  of  local  weathering  are  supplemented 
rather  by  the  rasping  and  trituration  that  go  with  transportation 
than  by  the  chemical  disintegration  that  characterizes  a  plant- 
bound  soil. 

No  special  conditions  need  be  postulated  as  to  the  initiation 
of  the  arid  cycle.  The  passive  earth's  crust  may  be  (relatively) 
uplifted  and  offered  to  the  sculpturing  agencies  with  any  struc- 
ture, any  form,  and  any  altitude,  in  dry  as  well  as  in  moist 
regions. 

Initial  Stage.  Let  consideration  be  given  to  an  uplifted  region 
of  large  extent  over  which  an  arid  climate  prevails.  Antecedent 
rivers,  persisting  from  a  previous  cycle  against  the  deformations 
by  which  the  new  cycle  is  introduced,  must  be  rare,  because  such 
rivers  should  be  large,  and  large  rivers  are  unusual  in  an  arid 
region.  Consequent  drainage  must  prevail.  The  initial  slopes  in 
each  basin  will  lead  the  wash  of  local  rains  toward  the  central 
depression,  whose  lowest  point  serves  as  the  local  base-level  for 
the  district.  There  will  be  as  many  independent  centripetal  sys- 
tems as  there  are  basins  of  initial  deformation,  for  no  basin  can 
contain  an  overflowing  lake,  whose  outlet  would  connect  two 
centripetal  systems ;  the  centripetal  streams  will  not  always 
follow  the  whole  length  of  the  centripetal  slopes ;  most  of  the 
streams  of  each  basin  system  will  wither  away  after  descending 
from  the  less  arid  highlands  to  the  more  arid  depressions.  Each 
basin  system  will  therefore  consist  of  many  separate  streams, 
which  may  occasionally,  in  time  of  flood  or  in  the  cooler  season 
of  diminished  evaporation,  unite  in  an  intermittent  trunk  river, 
and  even  form  a  shallow  lake  in  the  basin  bed,  but  which  will  ordi- 
narily exist  independently  as  disconnected  headwater  branches. 


298  PHYSIOGRAPHIC  ESSAYS 

Youthful  Stage.  In  the  early  stage  of  a  normal  cycle  the  relief 
is  ordinarily  and  rapidly  increased  by  the  incision  of  consequent 
valleys  by  the  trunk  rivers  that  flow  to  the  sea.  In  the  early 
stage  of  the  arid  cycle  the  relief  is  slowly  diminished  by  the 
removal  of  waste  from  the  highlands,  and  its  deposition  on  the 
lower  gentler  slopes  and  on  the  basin  beds  of  all  the  separate 
centripetal  drainage  systems.  Thus  all  the  local  base-levels  rise. 
The  areas  of  removal  are  in  time  dissected  by  valleys  of  normal 
origin;  if  the  climate  is  very  arid,  the  uplands  and  slopes  of 
these  areas  are  either  swept  bare,  or  left  thinly  veneered  with 
angular  stony  waste,  from  which  the  finer  particles  are  carried 
away  almost  as  soon  as  they  are  weathered ;  if  a  less  arid  climate 
prevails  on  the  uplands  and  highlands,  the  plants  that  they  sup- 
port will  cause  the  retention  of  a  larger  proportion  of  finer  waste 
on  the  slopes.  The  areas  of  deposition  are,  on  the  other  hand, 
given  a  nearly  level  central  floor  of  fine  waste,  with  the  varied 
phenomena  of  shallow  lakes,  playas,  and  salinas,  surrounded  with 
graded  slopes  of  coarser  waste.  The  deposits  thus  accumulated 
will  be  of  variable  composition  and,  toward  the  margin,  of  irreg- 
ular structure.  The  coarser  deposits  will  exhibit  a  variety  of 
materials,  mechanically  comminuted,  but  not  chemically  disinte- 
grated, and  hence  in  this  respect  unlike  the  less  heterogeneous 
deposits  of  humid  climates  from  which  the  more  easily  soluble 
or  decomposable  minerals  have  been  largely  removed.  The  finer 
deposits  will  vary  from  sand  and  clay  to  salt  and  gypsum.  The 
even  strata  that  are  supposed  to  characterize  lake  deposits  may 
follow  or  precede  irregular  or  cross-bedded  strata,  as  the  lake 
invades  or  is  invaded  by  the  deposits  of  streams  or  winds. 
While  many  desert  deposits  may  be  altogether  devoid  of  organic 
remains,  others  may  contain  the  fossils  of  land,  stream,  or  lake 
organisms. 

The  Basin  range  province  of  the  western  United  States  gives 
examples  of  dissected  mountains  from  which  descend  many 
withering  streams  that  belong  to  separate  drainage  systems  of 
the  kind  above  described,  and  of  basins  aggraded  with  the 
waste  from  the  dissected  mountains.  Trunk  streams  are  rare. 
The  initial  relief  has  been  decreased,  although  the  basin  floors 
are  from  three  thousand  to  five  thousand  feet  above  sea-level. 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     299 

Persia  and  Tibet  give  further  illustrations  of  the  same  relation. 
In  the  latter  region  the  intermontane  basins  often  contain  saline 
lakes  ;  but  the  stage  of  development  there  reached  is  not  yet 
clear,  because  the  origin  of  the  ranges  and  basins  is  not,  as  a 
rule,  considered  by  Tibetan  explorers.  It  should  not,  however, 
be  inferred  that  the  separation  of  the  many  drainage  systems  in 
regions  such  as  those  of  Persia  and  Tibet  is  the  result  of  any 
special  peculiarity  in  the  initial  deformation  of  the  surface  essen- 
tially unlike  the  deformation  of  other  regions  of  normal  climate 
where  large  unified  drainage  systems  are  the  rule.  The  latter 
regions  may  initially  have  had  as  many  basins  of  deformation  as 
the  former,  but  the  more  plentiful  rainfall  of  normal  climate  has 
enabled  their  rivers  to  cut  down  the  basin  rims.  This  principle 
has  been  pointed  out  by  Penck  (a,  87 ;  b,  169)  and  others.  The 
initial  relief  may  be  of  coarse  pattern,  as  in  central  Asia,  where 
the  vast  aggraded  plains  of  eastern  and  western  Turkestan  are 
separated  by  a  broadly  uplifted  and  deeply  dissected  mountainous 
area;  or  of  finer  pattern,  as  in  the  Basin  range  province  just 
mentioned,  where  many  small  ranges  separate  nearly  as  many 
small  basins.  The  progress  of  evolution  through  the  cycle,  and 
the  arrangement  of  forms  at  successive  stages,  will  be  much 
affected  by  these  unlike  initial  conditions. 

Streams,  floods,  and  lakes  are  the  chief  agencies  in  giving 
form  to  the  aggraded  basin  floors,  as  well  as  to  the  dissected 
basin  margins  in  the  early  stages  of  the  cycle ;  but  the  winds 
also  are  of  importance  :  they  do  a  certain  share  of  erosion  by 
sand-blast  action;  they  do  a  more  important  work  of  transporta- 
tion by  sweeping  the  grariular  waste  from  exposed  uplands  and 
depositing  it  in  more  sheltered  depressions,  and  by  raising  the 
finer  dust  high  in  the  air  and  carrying  it  far  and  wide  before  it 
is  allowed  to  settle.  Wind  action  is,  moreover,  peculiar  in  not 
being  guided  by  the  slopes  or  restrained  by  the  divides  which 
control  streams  and  stream  systems.  It  is  true  that  the  winds, 
like  the  streams,  tend  in  a  very  general  way  to  wear  down  the 
highlands  and  to  fill  up  the  basins  ;  but  sand  may  be  drifted  up- 
hill,—  dunes 'may  be  seen  climbing  strong  slopes  and  escarp- 
ments in  Arizona  and  Oregon,  —  while  fine  dust  carried  aloft 
in  whirlwinds  and  dust  storms  is  spread  about  by  the  upper 


300  PHYSIOGRAPHIC  ESSAYS 

currents  with  little  regard  to  the  slopes  of  the  land  surface  far 
below.  Sand  may  be  drifted,  and  dust  may  be  in  this  way  carried 
outside  of  the  arid  region  from  which  it  was  derived.  Wind 
erosion  may,  furthermore,  tend  to  produce  shallow  depressions 
or  hollows ;  for  the  whole  region  is  the  bed  of  the  wind,  and  is 
therefore  to  a  certain  extent  analogous  to  the  bed  of  a  river, 
where  hollows  are  common  enough ;  but  in  the  early  stages  of  the 
cycle  in  a  region  where  the  initial  relief  was  strong,  the  action 
of  the  wind  is  not  able  to  make  hollows  on  the  original  slopes 
that  are  actively  worked  upon,  and  for  a  time  even  steepened, 
by  streams  and  floods.  Hence  in  the  youthful  stage  wind-blown 
hollows  are  not  likely  to  be  formed. 

•  It  is  important  to  notice  that  a  significant,  though  small,  share 
of  wind-swept  or  wind-borne  waste  may  be  carried  entirely  out- 
side of  or  "  exported  "  from  an  arid  region.  It  may  be  deposited 
on  neighboring  lands,  where  it  will  be  held  among  the  grass  of  a 
less  arid  climate,  as  long  ago  suggested  by  Richthofen  ;  it  may 
even  be  held  down  on  coastal  lands  by  the  dew,  as  has  been 
suggested  for  certain  districts  in  Morocco  by  Fischer;  it  may 
fall  into  the  sea,  as  is  proved  by  the  sand  that  gives  a  ruddy 
tinge  to  the  sails  of  vessels  in  the  Atlantic  to  leeward  of  the 
Sahara,  and  by  the  sand  grains  that  are  dredged  up  with  true 
pelagic  deposits  from  the  bottom  of  that  part  of  the  Atlantic. 
It  may  therefore  be  expected  that  the  progress  of  erosion  and 
waste  exportation  in  a  desert  region  will  be  associated  with  the 
deposit  of  fine  waste,  as  in  loess  sheets,  on  the  neighboring  less 
arid  regions,  especially  down  the  course  of  the  prevailing  winds. 
In  regions  of  weak  and  variable  winds  the  process  of  sand  and 
dust  exportation  must  be  extremely  slow ;  in  regions  of  steady 
winds  it  must  still  be  vastly  slower  than  the  ordinary  rate  of 
waste  removal  in  young  or  mature  regions  of  plentiful  rainfall 
and  normal  rivers.  Yet  it  is  by  this  slow  process  of  exportation 
that  the  mean  altitude  of  an  arid  region,  such  as  is  here  con- 
sidered, will  be  continually  decreased ;  hence  the  earlier  stages 
of  the  arid  cycle  are  expectably  longer  than  the  corresponding 
stages  of  the  normal  cycle. 

In  the  normal  cycle  the  youthful  stage  is  characterized  by  the 
headward   growth   of  many  subsequent   streams,  chiefly  along 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     301 

belts  of  weak  structures  that  are  laid  bare  on  the  valley  sides  of 
the  larger  consequent  streams.  In  the  arid  cycle  subsequent 
streams  have  a  smaller  opportunity  for  development ;  first,  be- 
cause all  the  belts  of  weak  structure  under  the  basin  deposits 
are  buried  out  of  reach ;  second,  because  in  the  absence  of  deep- 
cutting  trunk  rivers,  many  belts  of  weak  structure  are  but  little 
exposed.  In  so  far,  however,  as  the  highlands  are  dissected  by 
their  headwater  consequent  streams,  subsequent  branches  may 
grow  out  and  diversify  the  slopes  and  rearrange  the  drainage. 

Mature  Stage.  Continued  erosion  of  the  highlands  and  divides, 
and  continued  deposition  in  the  basins,  may  here  and  there  pro- 
duce a  slope  from  a  higher  basin  floor  across  a  reduced  part 
of  its  initial  rim  to  a  lower  basin  floor.  Headward  erosion  by 
the  consequent  or  subsequent  streams  of  the  lower  basin  will 
favor  this  change,  which  might  then  be  described  as  a  capture 
of  the  higher  drainage  area.  Aggradation  of  the  higher  basin  is 
equally  important,  and  a  change  thus  effected  might  be  described 
as  an  invasion  of  the  lower  basin  by  waste  from  the  higher  one ; 
this  corresponds  in  a  belated  way  to  the  overflow  of  a  lake  in  a 
normal  cycle.  There  may  still  be  no,  persistent  stream  connect- 
ing the  two  basins,  but  whenever  rain  falls  on  the  slope  that 
crosses  the  original  divide,  the  wash  will  carry  waste  from  the 
higher  to  the  lower  basin.  Thus  the  drainage  systems  of  two 
adjacent  basins  coalesce,  and  with  this  a  beginning  is  made  of 
the  confluence  and  integration  of  drainage  lines  which,  when 
more  fully  developed,  characterize  maturity.  The  intermittent 
drainage  that  is  established  across  the  former  divide  may  have 
for  a  time  a  rather  strong  fall ;  as  this  is  graded  down  to  an 
even  slope,  an  impulse  of  revival  and  deeper  erosion  makes  its 
way,  wave-like,  across  the  floor  of  the  higher  basin  and  up  all  its 
centripetal  slopes.  The  previously  aggraded  floor  will  thus  for 
a  time  be  dissected.with  a  bad-land  expression  and  then  smoothed 
at  a  lower  level ;  the  bordering  waste  slopes  will  be  trenched 
and  degraded.  At  the  same  time  the  lower  basin  floor  will  be 
more  actively  aggraded.  If  there  is  a  sufficient  difference  of  alti- 
tude between  the  two  basins,  all  the  waste  that  had  been,  in  a 
preliminary  or  youthful  view  of  the  case,  gathered  in  the  higher 
basin,  will  in  time  be  transferred  to  the  lower  basin;  and  thus  a 


302  PHYSIOGRAPHIC  ESSAYS 

larger  relation  of  drainage  lines,  a  longer  distance  of  intermittent 
transportation,  a  more  continuous  area  of  bed  rock  in  the  higher 
areas,  and  a  more  general  concentration  of  waste  in  the  lowest 
basins  will  be  established.  The  higher  local  base-levels  are  thus, 
by  a  process  of  slow,  inorganic  natural  selection,  replaced  by  a 
smaller  and  smaller  number  of  lower  and  lower  base-levels ;  and 
with  all  this  goes  a  headward  extension  of  graded  piedmont 
slopes,  a  deeper  dissection  of  the  highlands,  and  a  better  devel- 
opment of  their  subsequent  and  adjusted  drainage.  The  proc- 
esses of  drainage  adjustment  are,  however,  at  the  best,  of  less 
importance  here  than  in  the  normal  cycle,  because  of  the. ab- 
sence of  main  valleys,  deep-cut  by  trunk  rivers,  and  the  result- 
ing deficient  development  of  deep-set  subsequent  streams,  as  has 
already  been  suggested. 

Some  changes  of  this  kind  have  probably  taken  place  in  the 
Basin-range  province  of  Utah  and  Nevada,  but  more  field  work 
will  be  needed  before  they  can  be  safely  pointed  out.  Indeed, 
it  seems  to  be  the  case  that  certain  changes  of  an  opposite  kind 
have  taken  place ;  the  long  intermontane  troughs  appear  to  be 
here  and  there  subdivided  into  separate  basins  by  the  undue 
growth  of  certain  detrital  fans  where  large  valleys  have  been 
opened  in  the  neighboring  ranges  ;  but  this  condition  of  things 
will  pass  when  the  mountains  are  worn  lower  and  the  waste  is 
discharged  from  them  less  actively. 

As  the  coalescence  of  basins  and  the  integration  of  stream 
systems  progress,  the  changes  of  local  base-levels  will  be1  fewer 
and  slower  and  the  obliteration  of  the  uplands,  the  development 
of  graded  piedmont  slopes,  and  the  aggradation  of  the  chief 
basins  will  be  more  and  more  extensive.  The  higher  parts  of 
the  piedmont  slopes  may  be  rock  floors,  thinly  and  irregularly 
veneered  with  waste,  as  has  been  described  by  Keyes  for  certain 
basins  (bolsons)  in  New  Mexico ;  here,  as  well  as  upon  the 
aggraded  slopes  and  plains,  sheet-flood  action  will  prevail,  as 
explained  by  McGee.  The  area  occupied  during  early  maturity 
by  the  three  different  kinds  of  surface  —  dissected  highlands 
or  mountains,  graded  piedmont  slopes  of  rock  or  waste,  and 
aggraded  central  plains  with  playas,  salinas,  or  lakes  —  will  de- 
pend on  the  initial  relief,  on  the  rock  structure  and  its  relation 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE      303 

to  desert  weathering,  on  the  percentage  of  material  exported 
by  the  winds,  and  on  the  climate  itself. 

It  is  worth  noting  that,  although  the  activity  of  streams  and 
floods  decreases  with  the  decrease  of  relief  and  of  slope,  the 
activity  of  the  winds  is  hardly  affected  as  maturity  advances. 
The  winds  do  not  depend  on  the  gradient  of  the  land  surface 
for  their  gravitative  acceleration ;  they  may  blow  violently  and 
work  efficiently  on  a  level  surface.  Whirlwinds  are,  indeed,  most 
active  on  true  plains.  It  may  be  that  smooth  plains  are  never 
swept  by  winds  so  violent  as  the  blasts  which  attack  highlands 
and  mountains ;  but  it  is  probable  that  the  effective  action  of 
the  winds  is  greater  on  a  generally  plain  surface  than  on  one  of 
strong  relief,  where  the  salient  ridges  and  peaks  consist  largely 
of  firm  rock,  and  where  the  loose  waste  is  sheltered  in  reentrant 
valleys.  Moreover,  it  is  in  very  great  part  on  the  plains  that  the 
winds  of  ordinary  strength  drift  the  sand  about,  and  from  the 
plains  that  whirlwinds  and  dust  storms  raise  the  finest  waste 
high  enough  for  exportation.  It  may  therefore  be  concluded 
that  the  work  of  the  winds  is  but  little,  if  any,  impaired  by  the 
general  decrease  of  relief  that  characterizes  advancing  maturity, 
and  hence  that  their  relative  importance  increases.  Moreover, 
the  scanty  rainfall  of  an  arid  region  will  be  decreased  as  its  ini- 
tial highlands,  which  originally  acted  as  rain  provokers,  are  worn 
down ;  hence,  as  the  relief  weakens,  the  winds  will  more  and 
more  gain  the  upper  hand  in  the  work  of  transportation.  It  is 
conceivable  that  the  rate  of  exportation  of  sand  and  dust  by 
the  winds  in  maturity  and  all  the  later  stages  of  an  arid  cycle  is 
more  rapid  than  the  removal  of  fine  soil,  partly  or  largely  in 
solution,  from  a  plant-covered  peneplain  in  the  later  stages  of 
a  normal  cycle  ;  thus  the  slower  work  of  the  earlier  stages  of 
an  arid  cycle  may  be  partly  made  good  by  the  relatively  more 
active  work  in  the  later  stages. 

As  the  processes  thus  far  described  continue  through  geo- 
logical periods,  the  initial  relief  will  be  .extinguished  even  under 
the  slow  processes  of  desert  erosion,  and  there  will  appear  in- 
stead large  rock-floored  plains  sloping  toward  large  waste-floored 
plains ;  the  plains  will  be  interrupted  only  where  parts  of  the 
initial  highlands  and  masses  of  unusually  resistant  rocks  here 


304  PHYSIOGRAPHIC  ESSAYS 

and  there  survive  as  isolated  residual  mountains.  At  the  same 
time,  deposits  of  loess  may  be  expected  to  accumulate  in  increas- 
ing thickness  on  the  neighboring  less  arid  regions.  The  altitude 
at  which  the  desert  plain  will  stand  is  evidently  independent  of 
the  general  base-level  —  or  sea-level  —  and  dependent  only  on 
the  original  form  and  altitude  of  the  region,  and  on  the  amount 
of  dust  that  it  has  lost  through  wind  transportation. 

The  most  perfect  maturity  will  be  reached  when  the  drainage 
of  all  the  arid  region  becomes  integrated  with  respect  to  a  single 
aggraded  basin  base-level,  so  that  the  slopes  lead  from  all  parts 
of  the  surface  to  a  single  area  for  the  deposition  of  the  waste. 
The  lowest  basin  area  which  thus  comes  to  have  a  monopoly  of 
deposition  may  receive  so  heavy  a  body  of  waste  that  some  of 
its  ridges  may  be  nearly  or  quite  buried.  Strong  relief  may  still 
remain  in  certain  peripheral  districts,  but  large  plain  areas  will 
by  this  time  necessarily  have  been  developed.  In  so  far  as  the 
plains  are  rock-floored,  they  will  truncate  the  rocks  without 
regard  to  their  structure. 

There  is  rfo  novelty  in  the  idea  that  a  mountainous  region  of 
interior  drainage  may  be  reduced  to  a  plain  by  the  double  proc- 
ess of  wearing  down  the  ranges  and  filling  up  the  basins,  and 
that  the  plain  thus  formed,  consisting  partly  of  worn-down  rock 
and  partly  of  built-up  waste,  will  not  stand  in  any  definite  rela- 
tion to  the  general  base-level  of  the  ocean  surface ;  yet  the  idea 
has  seldom  been  applied  in  the  interpretation  of  uplifts  by  the 
physiographic  method.  In  the  case  of  the  plateaus  that  are  now 
trenched  by  the  Colorado  river  in  northern  Arizona,  for  example, 
it  has  usually  been  tacitly  postulated  that  the  base-level  with 
respect  to  which  they  were  widely  denuded  in  the  pre-canon 
cycle  was  the  normal  base-level  of  the  ocean,  and  from  this  pos- 
tulate it  has  been  argued  that  the  cycle  of  canon  erosion  was 
introduced  by  a  strong  uplift.  My  own  opinion  has  agreed  with 
that  of  Button  and  others  in  this  respect.  Yet  it  is  not  to-day 
easily  demonstrated  that  the  Arizona  plateaus  had  exterior 
drainage  at  the  time  of  their  wide  denudation;  and  until  ex- 
terior drainage  is  shown  to  have  obtained,  the  altitude  of  the 
plateau  region  during  its  denudation  must  remain  uncertain. 
There  are,  however,  several  facts  which  point  to  the  correctness 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     305 


of  the  generally  accepted  view  :  the  course  of  the  Colorado  river 
through  the  Kaibab  cannot  easily  be  explained  as  having  origi- 
nated in  the  present  cycle ;  it  appears  to  have  been  established 
earlier ;  and  it  is  doubtful  whether  there  are  late  Tertiary  basin 
deposits  within  the  desert  area,  or  wind-carried  sand  and  loess 
deposits  in  the  area  to  the  eastward  (leeward)  of  sufficient 
volume  to  represent  the  great  volume  of  material  removed  in 
the  degradation  of  the  plateaus. 

In  the  case  of  truncated  uplands  elsewhere  —  that  is,  uplands 
whose  surface  truncates  their  structure,  as  in  the  central  plateau 
of  France  —  it  is  generally  a  tacit  postulate,  if  not  a  proved  con- 
clusion, that  the  climate  during  their  truncation  was  not  arid, 
and  hence  it  is  inferred  that  they  were  worn  down  as  peneplains 
with  respect  to  normal  base-level,  and  that  they  have  been  up- 
lifted since ;  this  aspect  of  the  problem  will  be  considered 
further  on.  In  the  meantime,  there  is  another  aspect  of  erosion 
in  arid  regions  which  has  not,  to  my  knowledge,  until  recently, 
received  attention. 

The  Beginning  of  Old  Age.  During  the  advances  of  drainage 
integration  the  exportation  of  wind-borne  waste  is  continued. 
At  the  same  time  the  tendency  of  wind  action  to  form  hollows 
wherever  the  .rocks  weather  most  rapidly  to  a  dusty  texture 
would  be  favored  by  the  general  decrease  of  surface  slopes,  and 
by  the  decrease  of  rainfall  and  of  stream  action  resulting  from 
the  general  wearing-down  of  the  highlands.  Thus  it  may  well 
happen  that  wind-blown  hollows  are  produced  here  and  there, 
through  the  mature  and  later  stages  of  the  cycle,  and  that  they 
will,  even  during  early  maturity,  interfere  to  a  greater  or  less 
degree  with  the  development  of  the  integrated  drainage  described 
above.  In  any  case,  it  may  be  expected  that  wind-blown  hollows 
will  in  late  maturity  seriously  interfere  with  the  maintenance  of 
an  integrated  drainage  system.  Thus  it  appears  that,  along  with 
the  processes  which  tend  toward  the  mature  integration  of  drain- 
age, there  are  other  processes  which  tend  toward  a  later  disin- 
tegration, and  that  the  latter  gain  efficiency  as  the  former  begin 
to  weaken.  A  strong  initial  relief  of  large  pattern,  a  quality  of 
rock  not  readily  reducible  to  dusty  waste,  and  an  irregular  move- 
ment of  light  winds  might  give  the  control  of  sculpture  to  the 


306  PHYSIOGRAPHIC  ESSAYS 

intermittent  streams  through  youth  and  into  maturity ;  in  such 
a  case  maturity  might  be  characterized  by  a  fully  integrated 
system  of  drainage  slopes,  with  insignificant  imperfections  in 
the  way  of  wind-blown  hollows.  In  a  second  region  an  initial 
form  of  weaker  relief,  a  quality  of  rock  readily  reducible  to  dust, 
and  a  steady  flow  of  strong  winds  might  favor  the  development 
of  wind-blown  hollows  or  basins,  and  here  the  process  of  drain- 
age disintegration  would  set  in  relatively  early  and  prevent  the 
attainment  of  mature  drainage  integration.  In  any  case,  as  soon 
as  the  process  of  drainage  disintegration  begins  to  predominate, 
maturity  may  be  said  to  pass  into  old  age. 

This  feature  of  the  arid  cycle  has  no  close  analogy  with  the 
features  recognized  in  the  normal  cycle.  In  the  latter  case  the 
drainage  systems  of  maturity  tend  on  the  whole  to  persist,  even 
though  the  streams  weaken  and  wander  somewhat  —  and  accord- 
ing to  theory  lose  some  of  their  adjustments  —  in  very  advanced 
old  age ;  in  the  former  case,  as  old  age  advances,  the  integrated 
and  enlarged  drainage  systems  of  maturity  are  broken  up  into 
all  manner  of  new  and  local,  small  and  variable,  systems.  The 
further  results  of  drainage  disintegration  in  the  later  stages  of 
the  cycle  are  even  more  peculiar. 

Leveling  without  Base- Leveling.  The  later  consequences  of 
erosion  in  an  extensive  arid  region  have  been,  as  far  as  my 
reading  goes,  first  and  recently  stated  by  Passarge  in  connection 
with  his  studies  of  the  arid  regions  of  South  Africa,  as  is  more 
fully  indicated  below. 

As  the  dissected  highlands  of  maturity  are  worn  down,  the 
rainfall  decreases,  and  the  running  streams  are  weakened  and 
extinguished ;  thus,  as  has  been  suggested  above,  the  winds  in 
time  would  appear  to  gain  the  upper  hand  as  agents  of  erosion 
and  transportation.  If  such  were  the  case,  it  would  seem  that 
great  inequalities  of  level  might  be  produced  by  the  excavation 
of  wide  and  deep  hollows  in  areas  of  weak  rocks.  As  long  as 
the  exportation  of  wind-swept  sand  and  of  wind-borne  dust  con- 
tinued, no  easily  defined  limit  would  be  found  for  the  depth  of 
the  hollows  that  might  thus  be  developed  in  the  surface,  for 
the  sweeping  and  lifting  action  of  the  wind  is  not  controlled  by 
any  general  base-level.  In  an  absolutely  rainless  region  there 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     307 

appears  to  be  no  reason  for  doubting  that  these  abnormal  in- 
equalities of  surface  might  eventually  produce  a  strong  relief  in 
a  stillstanding  land  of  unchanging  climate,  but  in  the  actual 
deserts  of  the  world  there  appears  to  be  no  absolutely  rainless 
region  ;  and  even  small  and  occasional  rainfalls  will  suffice,  espe- 
cially when  they  occur  suddenly  and  cause  floods,  as  is  habitual 
in  deserts,  to  introduce  an  altogether  different  regime  in  the 
development  of  surface  forms  from  the  rock  hills  and  hollows 
which  would  prevail  under  the  control  of  the  winds  alone.  The 
prevailing  absence  of  such  hill-and-hollow  forms,  and  the  gen- 
eral presence  of  graded  wadies  and  of  drainage  slopes  in  desert 
regions,  confirm  this  statement. 

As  soon  as  a  shallow  wind-blown  hollow  is  formed,  that  part 
of  the  integrated  drainage  system  which  leads  to  the  hollow  will 
supply  waste  to  it  whenever  rain  falls  there ;  the  finer  waste 
will  be  blown  away,  the  coarser  waste  will  accumulate,  and  thus 
the  tendency  of  the  winds  to  over-deepen  local  hollows  will  be 
spontaneously  and  effectively  counteracted.  As  incipient  hollows 
are  formed  in  advancing  old  age,  and  the  maturely  integrated 
drainage  system  disintegrates  into  many  small  and  variable  sys- 
tems, each  system  will  check  the  deepening  of  a  hollow  by  wind 
action ;  hence  no  deep  hollow  can  be  formed  anywhere  so  long 
as  occasional  rain  falls. 

It  is  conceivable  that,  in  some  special  cases,  there  might  be  a 
peculiar  balance  of  the  various  factors  involved  which  would 
result  in  the  development  of  wind-carved  hills  and  hollows,  even 
if  the  region  were  not  absolutely  rainless.  The  occurrence  of 
permeable  sandstones  might  favor  such  a  result,  because  the 
rain  falling  on  them  would  sink  into  the  ground  instead  of  run- 
ning off  of  it,  while  fine  grains  weathered  from  the  sandstone 
would  be  disposed  of  by  the  winds.  But  for  the  present  no 
desert  sandstone  region  with  hills  and  hollows  is  known,  while 
such  regions  with  hills  and  valleys  are  common.  Hence  it  must 
be  inferred  that  even  in  sandstone  deserts  the  occasional  rains 
suffice  to  wash  the  surface  and  to  prevent  the  formation  of  any- 
thing more  than  very  shallow  depressions. 

As  the  drainage  becomes  more  and  more  disintegrated,  and 
the  surface  of  the  plain  is  slowly  lowered,  rock  masses  that  most 


308  PHYSIOGRAPHIC  ESSAYS 

effectually  resist  dry  weathering  will  remain  as  monadnocks — 
Inselberge,  as  Bornhardt  and  Passarge  call  them  in  South  Africa. 
At  the  same  time  the  waste  will  be  washed  away  from  the  gather- 
ing grounds  of  maturity  and  scattered  in  the  shallow  hollows 
that  are  formed  here  and  there  by  the  winds  as  old  age  ap- 
proaches. The  removal  of  the  basin  deposits  by  the  winds  may 
be  delayed  where  the  hygroscopic  action  of  saline  clays  keeps 
the  surface  firm  ;  but  wherever  the  integrated  centripetal  slopes 
are  locally  reversed  by  the  hollowing  action  of  .the  wind,  some 
of  the  central  deposits  will  be  washed  back  again  and  exposed 
to  renewed  search  for  fine  material  by  the  wind,  and  thus  a  larger 
and  larger  part  of  the  central  waste  will  be  redistributed  and 
exported.  As  there  is  no  relation  of  parts  in  the  winds  analo- 
gous to  that  of  small  branch  and  large  trunk  streams  in  river 
systems,  the  surface  eroded  by  the  winds  need  not  slope  toward 
any  central  area,  but  may  everywhere  be  worn  down  essentially 
to  the  same  level.  The  surface  ever  wearing  down,  the  waste 
ever  washed  irregularly  about  by  the  variable  disintegration  of 
the  drainage  system  and  continually  exported  by  the  winds,  a 
nearly  level  rock  floor,  nowhere  heavily  covered  with  waste  and 
everywhere  slowly  lowering  at  the  rate  of  sand  and  dust  expor- 
tation, is  developed  over  a  larger  and  larger  area ;  and  such  is 
the  condition  of  quasi-equilibrium  for  old  age.  At  last,  as  the 
waste  is  more  completely  exported,  the  desert  plain  may  be 
reduced  to  a  lower  level  than  that  of  the  deepest  initial  basin ; 
and  then  a  rock  floor,  thinly  veneered  with  waste,  unrelated  to 
normal  base-level,  will  prevail  throughout  —  except  where  monad- 
nocks  still  survive.  This  is  the  generalization  that  we  owe  to 
Passarge  ;  it  seems  to  me  secondary  in  value  only  to  Powell's 
generalization  concerning  the  general  base-level  of  erosion.  So 
long  as  the  sea  is  held  out,  it  would  seem  that  a  desert  surface 
might  be  worn  even  below  sea-level,  as  certain  writers  have 
pointed  out  in  a  general  way  (Penck,  b,  167);  but  that  such  a 
desert  should  persistently  maintain  a  plain  surface  while  it  is 
slowly  worn  lower  and  lower  is  a  surprising  result  of  deduction. 
Little  wonder  that  an  understanding  of  the  possible  development 
of  rock-floored  deserts  of  this  kind,  independent  of  base-level, 
was  not  reached  inductively  in  western  America ;  for  there  has 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     309 

been  so  much  disturbance  in  the  way  of  fracture  and  uplift  in 
that  region  during  Mesozoic,  Tertiary,  and  Quaternary  time  that 
the  attainment  of  arid  old  age  has  not  been  permitted  ;  but  that 
the  problem  was  not  solved  deductively  by  the  present  genera- 
tion of  American  physiographers  before  it  was  encountered  and 
solved  by  others  in  Africa  serves  to  show  how  insufficient  still 
is  the  use  of  the  deductive  method  among  us. 

Passarge  writes  that  his  attention  has  been  called  to  the  diffi- 
culty of  explaining  the  vast  plain  surfaces  of  South  Africa  by 
wind  action,  because  the  wind  has  no  base-level  of  erosion, 
and  it  therefore  can  and  must  excavate  considerable  hollows 
in  rock  areas  whose  waste  it  can  easily  remove.  He  adds  that 
this  difficulty  disappears  as  soon  as  rain  works  with  the  wind, 
since  the  rain  constantly  seeks  to  wash  waste  into  the  hollows 
formed  by  the  wind,  whose  tendency  to  make  hollows  is  thereby 
counteracted.  \ 

The  Verity  of  the  Arid  Cycle.  The  Reductive  method  by 
which  most  of  the  preceding  paragraphs  are  characterized  may 
be  regarded  by  some  readers  as  reaching  too  far  into  the  field 
of  untestable  speculation.  It  is  true  that  the  examples  of  ob- 
served forms,  by  which  the  deduced  forms  of  every  stage  should 
be  matched,  are  as  yet  not  described  in  sufficient  number ;  but 
this  may  be  because  desert  regions  have  not  yet  been  sufficiently 
explored  with  the  principles  herein  set  forth  —  particularly 
Passarge's  law  —  in  mind.  On  the  other  hand,  the  examples  of 
desert  plains  in  South  Africa,  described  by  Passarge  as  plains 
of  the  Bechuana  (Betschuana)  type,  suffice  to  show  that  the 
stage  of  widespread  desert  leveling  has  actually  been  reached 
in  that  region,  and  thus  justify  all  the  earlier  stages  ;  for,  how- 
ever many  land  movements  may  have  interrupted  the  regular 
progress  of  preceding  cycles,  the  occurrence  of  widespread  rock 
plains  proves  that  at  least  the  present  cycle  of  arid  erosion  has 
been  long  continued  without  disturbance. 

The  levelness  of  the  plains  over  wide  areas  is  especially  em- 
phasized. Isolated  mountains  rise  above  the  plains  ;  and  the 
combination  of  the  two  unlike  forms  is  described  under  the  term 
Inselberglandschaft,  suggested  by  Bornhardt.  Passarge  states 
that  these  desert  plains  are  not  undulating  with  low  hills,  but 


310  PHYSIOGRAPHIC  ESSAYS 

are  true  plains  of  great  extent,  from  which  the  isolated  residual 
mountains  rise  like  islands  from  the  sea.  The  residuals  may  be 
low  mounds  only  a  few  meters  high,  or  lofty  mountain  masses 
rising  several  thousand  meters  above  the  plains.  The  plain  sur- 
rounds the  steep  slope  of  the  mountains  with  a  table-like  even- 
ness ;  there  is  no  transitional  belt  of  piedmont  hills,  and  no 
intermediate  slope  (£,  194).  The  mountains  consist  of  resistant 
rocks  such  as  granite,  diorite,  gabbro,  quartzite,  etc.,  granite 
being  the  most  frequent ;  the  plains  are  of  more  easily  eroded 
rocks  such  as  gneiss,  schists,  slates,  sandstones,  and  limestones. 
The  bedding  of  the  rocks  is  not  flat,  but  disturbed ;  the  plain 
therefore  truncates  the  rock  structures.  The  rocks  are  not  deeply 
decomposed,  but  are  relatively  fresh.  The  products  of  weather- 
ing are  usually  spread  as  a  thin  veneer  on  the  plain ;  the  waste 
does  not  lie  in  place  on  the  rocks  from  which  it  was  weathered, 
but  has  been  drifted  about  by  wind  and  flood  and  has  gathered 
in  slight  depressions.  The  waste  veneer  increases  the  smooth- 
ness of  the  plain,  but  the  rock  surface  is  also  a  plain,  as  may 
be  seen  in  the  edge  of  water  channels,  as  well  as  where  the 
veneer  is  absent  (b,  195).  Neighboring  areas  contain  exten- 
sive deposits  of  irregular  strata  whose  composition  and  want  of 
fossils  indicate  their  desert  origin,  as  will  be  referred  to  again 
below.  Various  additional  details  are  given,  with  the  conclusion 
as  above  quoted  :  these  rock-floored  plains  are  not  uplifted  pene- 
plains, but  are  the  product  of  desert  erosion  unrelated  to  normal 
base-level,  in  which  occasional  water  action  has  cooperated  with 
more  persistent  wind  action. 

The  scheme  of  the  arid  cycle  thus  seems  to  be  as  well  sup- 
ported by  appropriate  facts  as  is  the  scheme  of  the  normal 
cycle ;  it  is,  indeed,  in  one  respect  even  better  supported,  for 
while  the  arid  African  plains  are  examples  of  old  desert  plains 
now  growing  still  older,  it  is  difficult  to  point  out  any  large 
peneplain  that  still  stands  close  to  the  base-level  with  respect  to 
which  it  was  worn  down. 

Contrasted  Consequences  of  Normal  Base-Leveling  and  Desert 
•Leveling.  While  the  theory  of  marine  planation  was  in  vogue, 
it  was  customary  to  interpret  all  evenly  truncated  uplands  — 
that  is,  uplands  whose  surface  truncates  their  rock  structure  — 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     3 1 1 

as  uplifted  plains  of  marine  abrasion,  more  or  less  dissected 
since  they  were  uplifted.  When  the  efficacy  of  sub-aerial  erosion 
was  recognized,  it  became  equally  customary  to  interpret  trun- 
cated uplands  as  once  base-leveled  and  afterward  uplifted  pene- 
plains. If  Passarge's  views  be  now  accepted,  it  follows  that  no 
truncated  uplands  should,  without  further  inquiry,  be  treated  as 
having  been  eroded  when  their  region  had  a  lower  stand  with 
respect  to  base-level ;  the  possibility  of  their  having  been  formed 
during  an  earlier  arid  climate  as  desert  plains,  without  regard 
to  the  general  base-level  of  the  ocean,  must  be  considered  and 
excluded  before  base-leveling  and  uplift  can  be  taken  as  proved. 
It  may  at  first  -appear  sufficient  to  say  that  high-standing 
desert  plains  can  have  been  made  only  in  those  regions  which 
are  now  desert,  but  this  easy  solution  of  the  problem  is  hardly 
convincing.  Climatic  changes  are  known  to  have  occurred  in 
the  past,  and  inasmuch  as  they  did  not  all  affect  areas  in  a  way 
that  is  sympathetic  with  the  present  arrangement  of  the  zones, 
the  possibility  of  a  former  different  distribution  of  deserts  from 
that  which  now  occurs  seems  to  be  open.  Pleistocene  climatic 
changes  of  the  glacial  kind  were  so  modern  and  short-lived  that 
they  have  little  bearing  on  the  possibility  of  earlier  climatic 
changes  of  another  order.  The  more  ancient  records  of  glacia- 
tion  are  so  distributed  as  to  demand  significant  rearrangement 
of  the  present  climatic  conditions.  The  existing  deserts  are, 
moreover,  of  two  kinds  with  respect  to  cause  :  some  deserts, 
like  those  of  Africa  and  Australia,  are  arranged  chiefly  with 
respect  to  the  trade-wind  belt ;  other  deserts,  like  those  of  cen- 
tral Asia  and  the  southwestern  United  States,  are  dependent 
for  the  most  part  on  the  extent  and  configuration  of  the  sur- 
rounding highlands.  When  we  go  back  as  far  as  Cretaceous 
time,  it  should  only  be  by  evidence  and  not  by  assumption  that 
we  are  led  to  regard  a  truncated  upland  of  that  date  as  having 
been  base-leveled  during  a  cycle  of  normal  climate  and  after- 
ward uplifted  and  dissected,  instead  of  having  been  leveled  above 
base-level  during  a  cycle  of  arid  climate,  and  dissected  in  con- 
sequence of  a  change  to  a  normal  climate.  A  century  ago 
demonstrated  movements  of  the  earth's  crust  were  matters,  of 
astonishment ;  witness  the  surprise  then  felt  at  the  discovery 


3I2 


PHYSIOGRAPHIC  ESSAYS 


of  fossilized  marine  shells  in  some  of  the  loftier  Alpine  ranges. 
To-day  the  crust  is  raised  and  lowered  on  the  evidence  of  dissected 
peneplains,  as  in  the  Appalachian  region,  without  exciting  re- 
mark ;  it  is  now  the  shifting  of  climatic  conditions  that  would 
cause  dissenting  surprise.  It  is  difficult  to  determine  how  far 
such  surprise  is  well  founded,  and  how  far  it  simply  reflects  the 
fashion  of  our  time.  Even  if  the  climatic  zones  have  always 
belted  the  earth  as  they  do  now,  the  desert  areas  that  depend 
on  the  configuration  of  land  and  water,  and  of  highlands  and 
lowlands,  have  certainly  varied  through  the  geological  ages. 
It  is  therefore  desirable,  wherever  the  question  of  "  uplifted  and 
dissected  peneplains  "  is  raised,  to  scrutinize  it  carefully,  and 
to  determine,  if  possible,  whether  it  is  really  the  attitude  of  the 
earth's  crust  or  the  condition  of  climate  that  has  been  changed. 
It  is  likewise  important  to  scrutinize  desert  plains,  now  stand- 
ing above  base-level,  to  see  if  they  may  not  have  been  formed 
normally  as  lowland  plains  of  erosion  and  afterward  uplifted.  It 
is  therefore  necessary  to  inquire  into  these  features  by  which 
base-leveled  peneplains  and  rock-floored  desert  plains  may  be 
distinguished,  even  though  the  former  may  be  uplifted  with  a 
change  to  an  arid  climate,  or  though  the  latter  may  be  depressed 
with  a  change  to  a  humid  climate. 

Passarge  holds  the  opinion  that  the  plains  of  the  Inselbergland- 
schaft  are  smoother  than  any  peneplain  can  be  ;  for  he  describes 
the  desert  plains  as  true  plains,  not  as  gently  undulating  sur- 
faces. He  states  that  water  is  not  competent  to  produce  such 
plains ;  its  power  of  erosion  works  chiefly  downward,  and  only 
by  exception  laterally;  and  he  concludes  that  although  long-con- 
tinued normal  erosion  may  produce  a  peneplain,  —  that  is,  a  low, 
undulating  hilly  surface, —  it  nevertheless  cannot  produce  a  sur- 
face like  that  of  the  plains  in  the  Inselberglandschaft.  But  how- 
ever difficult  it  may  be  to  wait,  in  imagination,  through  the  ages 
required  to  wear  a  low  hilly  region  down  to  less  and  less  relief 
by  the  weakened  processes  of  weather  and  water  erosion  in  the 
latest  stages  of  the  normal  cycle,  there  are  certainly  some  trun- 
cated uplands,  ordinarily  taken  to  be  uplifted  peneplains,  whose 
interstream  uplands  are  astonishingly  even,  and  whose  surface 
must  have  been,  before  dissection,  very  nearly  plain  over  large 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     313 

areas ;  hence  it  does  not  seem  to  me  altogether  certain  that  a 
greater  and  a  less  degree  of  flatness  can  be  taken  to  distinguish 
the  two  classes  of  plains. 

A  plain  of  erosion  lying  close  to  sea-level  in  a  region  of  nor- 
mal climate,  and  therefore  traversed  by  rivers  that  reach  the 
sea  but  that  do  not  trench  the  plain,  might  conceivably  be  a 
depressed  desert  plain  standing  long  enough  in  a  changed  climate 
to  have  become  cloaked  with  local  soils ;  but  it  is  extremely 
unlikely  that  the  depression  of  a  desert  plain  could  place  it  so 
that  it  should  slope  gently  to  the  seashore,  and  that  its  new- 
made  rivers  should  not  dissect  it,  and  that  there  should  be  no 
drifted  sands  and  loess  sheets  on  adjoining  areas,  and  no  signs 
of  submergence  on  neighboring  coasts.  An  untrenched  plain 
of  erosion  in  such  an  attitude  would  be  properly  interpreted  as 
the  result  of  normal  processes,  long  and  successfully  acting  with 
respect  to  normal  base-level.  There  would  therefore  appear  to 
be  no  serious  danger  of  confusing  an  actual  peneplain  of  normal 
origin,  still  standing  close  to  base-level,  with  a  depressed  plain 
of  desert  origin.  For  the  reasons  above  given  I  am  not  dis- 
posed to  follow  Passarge  in  the  suggestion  that  the  old  land 
mass  of  Guiana  may  be  an  Inselberglandschaft  in  the  process  of 
destruction.  He  cites  it  as  a  flat,  gently  undulating  surface  of 
gneiss,  above  which  rise  knobs  and  mountains  of  granite ;  the 
divides  are  so  low  that  one  may  pass  in  canoe  between  the 
headwaters  of  the  Orinoco  and  Amazon  systems  (b,  194).  Until 
further  details  are  given,  it  would  seem  appropriate  to  regard 
this  region,  like  the  interior  of  Brazil  to  which  Lapparent  refers 
(a,  148),  as  an  example  of  a  normal  peneplain  not  raised  so  as 
to  be  attacked  by  its  rivers. 

In  the  same  way  a  high-standing  plain  of  erosion  in  a  desert 
region  might  be  possibly  explained  as  an  evenly  uplifted  pene- 
plain whose  climate  had  in  some  way  been  changed  from  humid 
to  arid,  whose  deep-weathered  soils  had  been  removed  and  re- 
placed by  thin  sheets  of  stony,  sandy,  or  saline  waste,  and  whose 
residual  reliefs  had  been  modified  to  the  point  of  producing 
shallow  basins.  But  in  this  case  there  should  be  some  indica- 
tions of  recent  uplift  around  the  margin  of  the  area,  either  in 
the  form  of  uplifted  marine  formations  whose  deposition  was 


314  PHYSIOGRAPHIC  ESSAYS 

contemporaneous  with  the  erosion  of  the  peneplain,  or  in  the 
form  of  fault  escarpments  separating  the  uplifted  from  the  non- 
uplifted  areas.  Moreover,  it  is  extremely  unlikely  that  the  uplift 
of  an  extensive  peneplain  could  place  it  in  so  level  a  position 
that  it  should  not  suffer  dissection  even  by  desert  agencies ; 
hence  a  high-standing  desert  plain  is  best  accounted  for  by  sup- 
posing that  it  has  been  leveled  in  the  position  that  it  now  occu- 
pies. According  to  Passarge,  there  are  no  sufficient  indications 
of  elevation  associated  with  the  South  African  desert  plains, 
and  their  explanation  as  the  result  of  long-continued  desert 
erosion  in  a  stillstanding  region  would  therefore  seem  to  be  as- 
sured. Whether  an  appropriate  deposit  of  wind-borne  waste  is 
to  be  found  on  neighboring  regions  is  not  yet  made  clear. 

It  should  not,  however,  be  overlooked  that  there  is  some 
danger  of  misreading  the  history  of  a  depressed  desert  plain 
which  has  been  by  a  moderate  amount  of  normal  weathering 
and  erosion  transformed  into  a  normal  peneplain,  and  of  an  up- 
lifted peneplain  which  has  been  by  a  moderate  amount  of  arid 
weathering  and  erosion  transformed  into  a  typical  desert  plain ; 
the  danger  of  error  here  is  similar  to  that  by  which  a  peneplain, 
wave-swept  and  scoured  during  submergence,  might  be  mis- 
taken for  a  normal  plain  of  marine  abrasion.  The  consequences 
of  error  are,  however,  not  so  serious  in  these  cases  of  actual 
plains  as  in  those  cases  which  may  arise  in  connection  with  dis- 
sected plains  ;  for  this  class  of  forms  is  of  common  occurrence, 
and  mistakes  in  explaining  their  origin  as  uplifted  peneplains 
or  as  changed-climate  desert  plains  might  therefore  be  of  fre- 
quent and  widespread  occurrence.  It  is  therefore  desirable  to 
search  out  those  features  by  which  normal  peneplains,  uplifted 
and'  dissected,  may  be  distinguished  from  desert  plains,  dissected 
after  a  change  to  humid  climate. 

If  a  normal  peneplain  be  uplifted,  its  already  adjusted  streams 
will  carry  their  adjustments  still  farther  in  the  new  cycle.  The 
high  degree  of  adjustment  of  streams  to  structures  in  the  Pennsyl- 
vania Appalachians  and  in  the  mediaeval  coastal  plain  of  central 
England  therefore  suggests  that  the  former  surface  of  truncation, 
beneath  which  the  present  lower  lands  have  been  etched  out, 
was  a  normal  peneplain,  uplifted.  If  a  normal  peneplain  be  tilted, 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     315 

its  depressed  part  will  soon  be  submerged  and  covered  with  ma- 
rine deposits ;  and  this  part  may,  by  later  uplift,  be  associated 
with  the  elevated  and  dissected  part.  The  marine  deposits  of 
our  Atlantic  and  Gulf  coastal  plain,  certain  basal  strata  of  conti- 
nental origin  excepted,  seem  to  lie  upon  a  depressed  part  of  the 
Appalachian  peneplain,  and  thus  confirm  the  evidence  of  normal 
base-leveling  derived  from  the  adjusted  drainage  of  the  uplifted 
and  dissected  part  of  the  same  peneplain ;  the  basal  strata  just 
mentioned  contain  fossil  land  plants  of  normal  climate  and  con- 
firm the  conclusion.  The  now  dissected  uplands  of  Brittany  and 
of  the  Ardennes  are  adjoined  or  overlapped  by  marine  deposits 
which  give  strong  suggestion  of  normal  peneplanation,  as  shown 
by  Lapparent  (b}.  Disturbances  of  the  arid  cycle  are  followed 
by  consequences  of  other  kinds. 

Interruptions  and  Modifications  of  the  Arid  Cycle.  A  land 
mass  suffering  erosion  under  an  arid  climate  may,  as  in  the 
normal  cycle,  suffer  interruption  in  the  regular  progress  of  its 
changes  by  movement  of  any  kind  at  any  stage  of  development. 
If,  for  example,  integration  of  drainage  has  advanced  so  far  that 
the  number  of  original  basins  is  reduced  by  half,  the  number 
may  be  increased  again  by  renewed  deformation ;  or  if  the  inte- 
gration of  drainage  has  reached  a  mature  stage,  the  drainage 
may  be  thrown  into  disorder  again  by  a  more  or  less  gentle 
warping  by  the  region.  In  all  such  cases  a  new  cycle  may  be 
regarded  as  having  been  initiated  ;  its  initial  forms  will  be  the 
eroded  forms  developed  during  the  preceding  incomplete  cycle, 
and  displaced  by  the  movements  through  which  the  preceding 
cycle  was  closed.  The  work  of  the  new  cycle,  thus  initiated, 
then  goes  on  as  before  ;  but  with  interruptions  of  this  kind  we 
are  not  here  particularly  concerned,  because  they  offer  no  special 
difficulty  of  explanation  or  interpretation. 

It  is  otherwise  when  interruptions  or  modifications  of  the  arid 
cycle  occur  after  old  age  is  well  advanced,  for  the  desert  plains 
then  developed  may,  under  certain  conditions,  come  to  imitate 
uplifted  undissected  peneplains,  as  has  already  been  partly  con- 
sidered in  the  preceding  section. 

Uniform  uplift  or  depression,  by  which  a  normal  peneplain  is 
so  immediately  and  significantly  modified,  will  not  interrupt  the 


316  PHYSIOGRAPHIC  ESSAYS 

regular  process  of  degradation  on  a  desert  plain  in  an  arid  cycle. 
It  is  perhaps  in  part  for  this  reason  that  actual  examples  of  rock- 
floored  desert  plains  appear  to  be  more  common  than  actual  ex- 
amples of  peneplains.  Depression  would  drown  a  peneplain,  and 
elevation  would  cause  its  dissection ;  but,  unless  carried  to  an 
extreme,  neither  of  these  movements  would  greatly  affect  the 
slow  degradation  of  a  desert  plain.  Unequal  movements,  whereby 
a  desert  plain  is  warped  or  slanted,  are  of  more  importance  and 
are  probably  of  more  common  occurrence. 

If  an  old  rock-floored  desert  plain  be  gently  warped  or  tilted, 
marine  submergence  is  not  likely  to  follow  immediately,  but  the 
regular  continuation  of  general  degradation  will  be  interrupted. 
The  patches  and  veneers  of  waste  will  be  washed  from  the  higher 
to  the  lower  parts  of  the  warped  surface ;  the  higher  parts, 
having  an  increased  slope,  may  be  somewhat  dissected,  and  will 
certainly  be  exposed  to  more  active  degradation  than  before, 
until  they  are  worn  down  to  a  nearly  level  plain  again.  The  lower 
parts  will  receive  the  waste  from  the  higher  parts,  and  the  con- 
tinuance of  this  process  of  concentration  will  in  time  cause  the 
accumulation  of  extensive  and  heavy  deposits  in  the  lower  areas. 
Such  deposits  will  be,  as  a  rule,  barren  of  fossils ;  the  composi- 
tion, texture,  and  arrangement  of  their  materials  will  indicate 
the  arid  conditions  under  which  they  have  been  weathered,  trans- 
ported, and  laid  down ;  their  structures  will  seldom  exhibit  the 
regularity  of  marine  strata,  and  they  may  reach  the  extreme 
irregularity  of  sand-dune  deposits.  If  warping  continues,  the 
desert  deposits  may  gain  great  thickness  ;  their  original  floor 
may  be  depressed  below  sea-level,  while  their  surface  is  still 
hundreds  or  thousands  of  feet  above  sea-level. 

Passarge  gives  a  number  of  instances,  which  he  groups  under 
the  Banda  type  (£,  200),  that  seem  to  illustrate  this  phase  of  the 
arid  cycle,  although  he  ascribes  the  barren  sandstones  of  this 
type  to  a  weakening  in  the  activity  of  the  winds  rather  than  to 
a  tilting  of  the  region.  Here  the  upper  parts  of  monadnocks  — - 
Inselberge  —  rise  above  a  broad  deposit  of  barren  continental 
sandstones ;  the  intermontane  plains,  being  buried,  are  matters 
of  inference.  Examples  of  this  type  are  mentioned  in  West 
Australia  as  well  as  in  Africa. 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     317 

If  a  change  from  an  arid  toward  a  moister  climate  causes  a 
drainage  discharge  to  the  sea,  a  dissection  of  the  plain  will  er/sue. 
The  valleys  thus  eroded  cannot  expectably  exhibit  any  great  de- 
gree of  adjustment  to  the  structures,  because  the  stream  courses 
will  result  from  the  irregular  patching  together  of  the  preexist- 
ing irregularly  disintegrated  drainage.  This  peculiar  character- 
istic, taken  together  with  the  absence  of  neighboring  uplifted 
marine  deposits,  will  probably  suffice  in  most  cases  to  distinguish 
desert  plains,  dissected  by  a  change  to  a  moister  climate,  from 
peneplains  dissected  in  consequence  of  uplift;  but  there  still  might 
be  confusion  with  peneplains  dissected  by  superposed  streams. 

Passarge  gives  two  types  of  desert  plains  with  a  modified 
climate.  The  first,  or  Kordofan  type  (b,  200),  is  marked  by  a 
slight  increase  of  rainfall,  sufficient  to  introduce  a  steppe  vege- 
tation, but  not  sufficient  to  form  rivers  that  shall  reach  the  sea. 
In  this  case  the  larger  residual  mountain  masses  come  to  be 
surrounded  by  washed  deposits  coarser  near  the  mountain  base, 
finer  farther  forward,  and  at  last  grading  into  swampy  areas  with 
dark  rich  soil.  Such  deposits  are  said  to  be  well  developed  in 
Kordofan,  where  the  buried  eroded  plain  between  the  mountains 
has  been  revealed  by  well  borings,  and  where  basins  in  the  buried 
plain  are  indicated  by  certain  unusual  accumulations  of  ground 
water.  The  second,  or  Adamaua  type  (b,  201),  includes  an  ex- 
ample of  more  abundant  rainfall,  and  therefore  exhibits  the 
dissection  of  what  is  taken  to  have  been  a  desert  plain  with 
Inselberge ;  but  the  relation  of  streams  to  structures  is  not 
mentioned.  Finally  a  Rovuma  type  (b,  202)  is  instanced  on  the 
authority  of  Bornhardt,  in  which  marine  Cretaceous  strata  of 
moderate  thickness  lie  upon  a  plain  whose  erosion  is  ascribed 
to  preexisting  desert  conditions. 

Diversion  of  Desert  Drainage  to  Exterior  Discharge.  The 
development  of  desert  plains  without  regard  to  normal  base-level 
is  possible  only  so  long  as  they  are  interior  basins  without  drain- 
age discharge  to  the  sea.  The  maintenance  of  this  essential 
condition  is  imperiled  by  small  area,  great  altitude,  no  inclosing 
mountains,  strong  exterior  slopes  to  the  sea,  and  the  occurrence 
of  heavy  rainfall  on  the  exterior  slopes.  A  small  desert  island 
would  have  no  room  for  the  production  of  interior  basins  by  the 


318  PHYSIOGRAPHIC  ESSAYS 

processes  of  initial  deformation,  or  for  their  maintenance  against 
the  attack  of  exterior  streams.  The  absence  of  inclosing  moun- 
tains around  a  continental  arid  region  would  permit  the  devel- 
opment of  escaping  drainage  systems,  so  that  when  mature 
integration  was  reached  it  might  be  developed  with  respect  to 
normal  base-level,  instead  of  with  respect  to  a  local  interior  base- 
level  ;  the  Sonoran  district  of  Mexico,  as  described  by  McGee, 
seems  to  offer  examples  of  this  kind.  Great  altitude  of  an  arid 
region  and  strong  exterior  slopes  would  give  strength  to  attack- 
ing exterior  streams,  and  no  advantage  to  the  interior  drainage ; 
some  of  the  basins  of  Tibet  have  already  been  invaded  by  the 
headwater  erosion  of  Himalayan  streams,  for  here  the  unfavor- 
able conditions  of  great  altitude  in  the  basins,  strong  exterior 
slopes,  and  heavy  exterior  rainfall  are  all  combined. 

On  the  other  hand,  great  area,  moderate  altitude,  inclosure  by 
mountain  barriers,  and  small  exterior  rainfall  are  favorable  to  the 
leveling  of  interior  desert  plains ;  and  to  these  favoring  condi- 
tions should  be  added  a  long  geological  period  of  quiet.  The 
greater  the  area  and  the  less  the  altitude,  the  less  the  opportu- 
nity that  exterior  streams  will  have  to  establish  relations  with  the 
interior  streams.  The  higher  the  inclosing  mountains,  the  longer 
the  interior  region  will  be  left  to  itself,  but  the  more  dust  it  will 
have  to  export  before  a  general  rock  floor  can  be  developed  ;  the 
desert  of  Gobi  offers  an  example  of  this  kind,  for  its  surface  must 
long  continue  to  suffer  aggradation  before  the  lofty  ranges  around 
its  depressed  surface  are  worn  down  to  its  level.  South  Africa 
would  seem  to  offer,  according  to  the  descriptions  by  Passarge, 
excellent  opportunity  for  the  successful  advance  of  the  arid  cycle 
far  into  old  age,  because  of  the  large  extent  of  the  land  area,  its 
sufficient  height  and  inclosure,  its  long-undisturbed  history,  and 
its  persistently  arid  climate. 

It  thus  seems  evident  that  the  conditions  necessary  for  desert 
leveling  are  actually  present  in  greater  or  less  degree  in  different 
parts  of  the  world. 

The  Scheme  of  the  Arid  Cycle  as  an  Aid  to  Observation.  The 
normal  cycle  has  now. been  practically  used  by  so  many  observ- 
ers, and  with  so  many  advantageous  results,  that  it  is  not  unfair 
to  expect  similar  advantage  from  the  use  of  the  arid  cycle  as  an 


GEOGRAPHICAL:  CYCLE  IN  AN  ARID  CLIMATE    319 

aid  to  observation  in  regions  where  it  may  be  appropriately  ap- 
plied. It  is  very  certain  that  many  observations  now  on  record 
with  regard  to  arid  regions  do  not  suffice  to  indicate  clearly 
the  stage  of  erosion  in  the  arid  cycle  which  such  regions  have 
reached ;  and  this  is  true  not  because  the  observers  had  either 
reason  or  wish  to  dissent  from  the  principles  of  the  scheme, 
but  because  it  was  not  consciously  present  in  their  minds  when 
the  observations  were  made.  The  same  is  often  true  of  the 
scheme  of  the  normal  cycle.  In  both  cases  the  failure  of  the  ob- 
servant explorer  to  refer  the  facts  that  he  finds  to  some  com- 
prehensive scheme  for  their  systematic  treatment  not  only 
results  in  the  accidental  overlooking  of  certain  significant  facts 
and  in  the  insufficient  description  of  others,  but  it  leaves  the 
reader  in  great  difficulty  when  he  tries  to  visualize  what  the 
observer  has  seen.  It  is  as  if  the  writer  and  the  reader  had  no 
common  language  in  which  the  observations  and  thoughts 
of  the  one  should  be  transmitted  to  the  other.  It  would  be  far 
otherwise  if  the  description  of  a  desert  region  were  undertaken 
systematically  in  view  of  what  seems  to  be  the  essential  sequence 
of  changes  in  all  deserts ;  that  is,  if  the  mountains  and  basins, 
the  rock  plains  and  waste  plains,  the  stream  channels,  the  playas, 
and  the  lakes,  were  all  treated  in  view  of  their  place  in  the  cycle 
of  changes  through  which  they  must  be  running.  It  is  chiefly  as 
an  aid  to  observation  and  record,  and  as  an  aid  to  the  under- 
standing of  observations  thus  recorded,  that  the  scheme  of  the 
arid  cycle  may  come  to  be  of  service. 

It  would  be  fitting  to  accompany  an  article  of  this  kind  with 
a  larger  number  of  actual  examples  than  have  here  been  intro- 
duced ;  but  in  the  endeavor  to  find  appropriate  examples,  the 
interpretation  of  the  observations  of  various  writers  in  view  of 
the  scheme  here  submitted  has  not  seemed  safe  enough  to  make 
it  worth,  while  to  undertake  it.  Safe  interpretation  needs  the 
conscious  application  of  the  scheme  by  the  observer  in  the  field. 
When  thus  applied,  it  is  to  be  hoped  that  the  scheme  of  the  arid 
cycle  may  lead  to  the  detection  of  many  facts  concerning  the 
evolution  of  land  forms  in  desert  regions  that  have  thus  far 
escaped  notice.  In  the  meantime  the  scheme  must  remain  in 
great  part  speculative. 


320  PHYSIOGRAPHIC  ESSAYS 

The  Bearing  of  the  Arid  Cycle  on  Theories  of  Elevation  and 
Depression.  There  is  another  aspect  of  the  case  which,  to  my 
mind,  not  only  gives  sufficient  justification  for  all  the  speculation 
here  presented,  but  makes  one  regret  that  it  was  not  undertaken 
sooner ;  for  in  that  case  certain  theoretical  discussions  would 
have  earlier  gained  a  firm  foundation. 

In  a  discussion  of  "  The  Bearing  of  Physiography  on  Suess's 
Theories"  (/),  I  have  urged  that  the  occurrence  of  high-standing 
and  isolated  peneplains  could  not  be  the  result  of  the  depression 
of  the  surrounding  lands  —  as  is  advocated  by  Suess  —  unless 
all  the  oceans  and  their  associated  lowlands  on  other  continents 
were  also  depressed  at  the  same  time  and  by  the  same  amount. 
The  necessity  of  accepting  world-wide  crustal  movements  may, 
however,  be  avoided,  if  the  high-standing  truncated  uplands  are 
regarded  as  the  result  of  local  uplifts  of  formerly  low-standing 
peneplains.  This  alternative  conclusion  is  so  simple  and  econom- 
ical that  it  is  accepted  by  many  geologists  and  geographers  ;  and 
it  seems  well  based  as  long  as  one  believes  that  the  even  uplands 
can  have  been  truncated  only  by  peneplanation  close  to  sea-level. 
As  soon,  however,  as  it  is  recognized  that  leveling  may  be  ac- 
complished in  an  arid  region  without  base-leveling,  it  is  no  longer 
necessarily  the  case  that  truncated  uplands  represent  uplifted 
peneplains ;  the  uplands  may  perhaps  be  parts  of  ancient  desert 
plains,  originally  denuded  at  their  present  altitude ;  and  until 
this  possibility  is  excluded,  their  isolated  position  may  be  ex- 
plained by  the  depression  of  the  surrounding  lands,  as  Suess  has 
supposed,  without  corresponding  change  in  the  level  of  the  oceans 
and  the  other  continents. 

In  the  case  of  the  truncated  uplands  or  horsts  of  central  Ger- 
many, there  appears  to  be  good  geological  reason  for  associating 
them  with  the  denuded  areas  of  the  Ardennes  and  of  Brittany,  as 
described  by  Lapparent  (£),  and  thus  concluding  that  they  were 
all  low-lying  peneplains  before  they  were  uplifted.  In  the  case 
of  the  plateaus  of  northern  Arizona,  the  evidence  of  normal  pene- 
planation is  less  complete ;  yet,  as  above  stated,  it  still  seems 
probable  that  these  plateaus  were  denuded  with  respect  to  nor- 
mal base-level,  and  that  the  canon  was  cut  across  their  surface 
in  consequence  of  a  later  uplift  with  respect  to  sea-level.  The 


GEOGRAPHICAL  CYCLE  IN  AN  ARID  CLIMATE     321 

Bural-bas-tau,  a  flat-topped  range,  and  the  associated  plateau-like 
highlands  in  the  Tian  Shan  system,  also  need  reconsideration 
in  view  of  the  possibility  of  desert  leveling.  I  have  treated  the 
Bural-bas-tau  (e,  f,  g),  and  Huntington  has  treated  the -associated 
highlands,  as  uplifted  peneplains.  Friederichsen,  on  the  other 
hand,  while  recognizing  the  highland  region  as  a  Denudations- 
flache,  has  hesitated  to  treat  it  as  a  once  low-lying  peneplain, 
because  of  the  possibility  of  its  erosion  above  base-level  in  a 
region  of  inland  drainage.  If  such  were  the  case,  it  need  not 
have  had  that  close  relation  to  base-level  that  is  to  be  expected 
in  a  normal  peneplain.  Nevertheless,  the  truncated  highlands 
and  mountain  tops  in  the  Tian  Shan  seem  to  be  closely  related 
to  the  still  low-lying  plains  of  erosion  that  are  drained  by  the  Hi 
river  to  lake  Balkash,  and  also  to  the  still  lower-lying  plain  of 
erosion  —  apparently  a  true  peneplain  —  that  is  drained  by  the 
Irtysh  and  the  Ob  to  the  Arctic  ocean ;  hence  the  probability 
still  seems  great  that  the  even  highlands  of  the  Bural-bas-tau 
represent  a  greatly  uplifted  plain,  even  though  that  plain  may 
have  been,  at  the  time  of  its  erosion,  a  desert  plain,  and  not  a 
normal  peneplain.  It  is  therefore  exceedingly  improbable  that 
the  even-topped  Bural-bas-tau,  standing  twelve  or  thirteen  thou- 
sand feet  above  sea-level,  gives  any  close  measure  of  the  alti- 
tude which  the  whole  region  possessed  while  the  great  erosion 
that  it  has  suffered  was  accomplished. 

REFERENCES 

Bornhardt.    Zur  Oberflachengestaltung  und  Geologic  Deutsch-Ostafrikas. 

Berlin,  1900. 

Davis,  W.  M.    (a)  "  Geographic   Classification,  illustrated  by  a  Study  of 
Plains,  Plateaus,  and  their  Derivatives."  Proceedings  of  the  Ameri- 
can Association,  XXXIII  (1884),  428-432. 
(6)  "  Geographic  Methods  in  Geologic  Investigation."    Nat.  Geog.  Mag., 

I  (1888),  11-26. 
(c}  "The    Geographical    Cycle."     Geog.  Jour.  (London),   XIV   (1899), 

481-584. 
(d}  "  Glacial  Erosion  in  France,  Switzerland,  and  Norway."    Proc.  Bost. 

Soc.  Nat.  Hist.,  XXIX  (1900),  273-322. 

(e)  "A  Flat-Topped  Range  in  the  Tian  Shan."    Appalachia,  X  (1904), 
277-284. 


322  PHYSIOGRAPHIC  ESSAYS 

(/)  "The  Bearing  of  Physiography  on  Suess'  Theories."   Am.  Jour.  Set., 

XIX  (1905),  265-273- 

(^•)  "A  Journey  across  Turkestan."     Explorations  in   Turkestan  (Car- 
negie Institution  Publications,  No.  26,  1905),  21-119. 
(Jt)  "  The  Complications   of  the   Geographical   Cycle."     Compte  Rendu, 

8me  Congres  International  de  Geographie. 
Friederichsen,  Petermanns  Mittheilungen,  XLIX,  136. 
Huntington,  E.    "  A  Geologic  and  Physiographic  Reconnaissance  in  Cen- 
tral  Turkestan."    Explorations  in    Turkestan   (Carnegie    Institution 
Publications,  No.    26,  1905),  157-216. 
Keyes,  C.  R.    "  Geological  Structure  of  New   Mexican   Bolson   Plains." 

Am.  Jour.  Sci.,  XV   (1903),  207-210. 

Lapparent,  A.  de.    (#)  Lemons  de  Geographie  Physique.     Paris,  1896. 
(b)  "  La  Question  de  Pdneplaines  envisagee  a  la  Lumiere  des  Faits  Geo- 
logiques."     Verhandlungen  des  VII.  International  Geographischen 
Kongresses  (1899},  (Berlin,  1901),  II,  213-220. 
McGee,  W.  J.    "  Sheetflood  Erosion."    Bull.  GeoLSoc.Am.,  VIII  (1897), 

87-112. 

Passarge,  S.    (a)  Die  Kalahari.    Berlin,  1904. 
(^)  "  Rumpfflache  und  Inselberge."    Zeitschrift  der  Deut.  Geol.  Gesell- 

schaft,  LVI  (1904),  Protokol,  193-209. 
(<:)  "  Die  Inselberglandschaften  im  Tropischen  Afrika."    Naturwiss.  Wo- 

chenschr.,  new  series,  III  (1904),  657-665. 
Penck,  A.    (a)  "  Einfluss  des  Klimas  auf  die  Gestalt  der  Erdoberflache." 

Verhandlungen  des  III.  Deut.  Geographentages  (1883),  78-92. 
(b}  "  Climatic   Features  in  the  Land  Surface."     Am.  Jour.   Sci.,    XIX 

(1905),  165-174- 
Walther,  J.    Das  Gesetz  der  Wiistenbildung.    Berlin,  1900. 


XVI 

PLAINS  OF  MARINE  AND  SUB-AERIAL 
DENUDATION 

Introduction.  Geologists  to-day  may  be  divided  into  two  schools 
on  the  basis  of  the  theories  which  they  hold  regarding  the 
origin  of  regions  of  comparatively  smooth  surface  from  which 
a  large  volume  of  overlying  rocks  has  been  removed.  'Thesi 
regions  occur  under  two  conditions :  first,  as  buried  ^Idlail 
on  which  an  unconformable  cover  of  later  formations  has  been 
deposited,  the  oldlands  being  now  more  or  less  locally  revealed 
by  the  dissection  or  stripping  of  the  cover  ;  second,  as  uplands  or 
plateaus  whose  once  even  surface  is  now  more  or  less  roughened 
by  the  erosion  of  valleys. 

The  older  school,  now  represented  chiefly  by  English  geolo- 
gists, follows  the  theory  of  Ramsay,  and  regards  these  even 
oldlands  as  plains  of  marine  denudation.  The  newer  school,  rep- 
resented chiefly  by  American  geologists,  but  also  by  a  number 
of  continental  European  geologists,  may  be  said  to  follow  Powell, 
who  first  emphatically  called  attention  to  the  possibility  of  pro-\ 
ducing  plains  by  long-continued  sub-aerial  denudation.  The  pres-  / 
ent  review  of  the  question  first  cites  a  number  of  extracts  from 
various  representatives  of  the  two  schools,  and  then  seeks  for  a 
test  by  which  the  rival  conclusions  may  be  distinguished,  the  test 
being  developed  from  a  study  of  the  natural  history  of  rivers. 

The  English  School.  Ramsay  is  believed  to  have  been  the  first 
advocate  of  marine  erosion  as  an  agency  for  the  production  of 
broad  plains  of  denudation.  In  describing  the  action  of  the  sea 
on  the  land  he  wrote : 

The  line  of  greatest  waste  on  any  coast  is  -the  average  level  of  the 
breakers.  The  effect  of  such  waste  is  obviously  to  wear  back  the  coast, 
the  line  of  denudation  being  a  level  corresponding  to  the  average  height  of 
the  sea.  Taking  unlimited  time  into  account,  we  can  conceive  that  any 
extent  of  laad  might  be  so  destroyed,  for  though  shingle  beaches  and  other 

323 


324  PHYSIOGRAPHIC  ASSAYS 

coast  formations  will  apparently  for  almost  any  ordinary  length  of  time 
protect  the  country  from  the  further  encroachments  of  the  sea,  yet  the  pro- 
tections to  such  beaches  being  at  last  themselves  worn  away,  the  beaches 
,  are  in  the  course  of  time  destroyed,  and  so,  unless  checked  by  elevation,  the 
waste  being  carried  on  forever,  a  whole  country  might  gradually  disappear. 
If  to  this  be  added  an  exceedingly  slow  depression  of  the  land  and  sea- 
bottom,  the  wasting  process  would  be  materially  assisted  by  this  depression, 
bringing  the  land  more  uniformly  within  the  reach  of  the  sea,  and  enabling 
the  latter  more  rapidly  to  overcome  obstacles  to  further  encroachments, 
created  by  itself  in  the  shape  of  beaches.  By  further  gradually  increasing 
the  depth  of  the  surrounding  water,  ample  space  would  also  be  afforded 
for  the  outspreading  of  the  denuded  matter.  To  such  combined  forces, 
namely,  the  shaving  away  of  coasts  by  the  sea,  and  the  spreading  abroad 
of  the  material  thus  obtained,  the  great  plain  of  shallow  soundings  which 
generally  surrounds  our  islands  is  in  all  probability  attributable  (a,  327). 

At  this  early  date  Ramsay  attributed  not  only  the  plains  them- 
selves, but  also  the  valleys  which  now  interrupt  ancient  and  up- 
lifted plains  of  denudation,  in  greatest  part  to  marine  action,  and 
allowed  but  little  effect  to  sub-aerial  denudation.  On  this  topic 
he  said : 

The  power  of  running  water  has  also  considerably  modified  the  surface, 
but  the  part  it  has  played  is  trifling  compared  with  the  effects  that  have 
sometimes  been  attributed  to  its  agency.  ...  In  the  larger  valleys,  where 
the  streams  are  sluggish,  instead  of  assisting  in  further  excavations,  the 
general  tendency  is  often  rather  to  fill  up  the  hollow  with  alluvial  accumu- 
lations, and  so  help  to  smooth  the  original  irregularities  of  the  surface 
(",  332,  333)- 

Thirty  years  later  Ramsay  ascribed  greater  results  to  sub-aerial 
agents.  Referring  to  the  generally  even  sky  line  of  South  Wales, 
he  wrote : 

The  inclined  line  that  touches  the  hill-tops  must  have  represented  a 
great  plain  of  marine  denudation.  Atmospheric  degradation,  aided  by  sea 
waves  on  the  cliffs  by  the  shore,  are  the  only  powers  I  know  of  that  can 
denude  a  country  so  as  to  shave  it  across  and  make  a  plain  surface  either 
horizontal  or  gently  inclined.  If  a  country  be  sinking  very  gradually  and 
the  rate  of  waste  by  all  causes  be  proportionate  to  the  rate  of  sinking, 
this  will  greatly  assist  in  the  production  of  the  phenomena  we  are  now 
considering. 

When  raised  out  of  the  water 

the  streams  made  by  its  drainage  immediately  began  to  scoop  out  val- 
leys, and  though  some  inequalities  of  contour  forming  mere  bays  may  have 


MARINE  AND  SUB-AERIAL  DENUDATION  325 

been  begun  by  marine  denudation  during  emergence,  yet  in  the  main  I 
believe  that  the  inequalities  below  the  [level  of  the  plain]  have  been  made 
by  the  influence  of  rain  and  running  water  (£,  497,  498). 

Greenwood,  an   early  advocate  of  the  efficacy  of  "  rain  and  \ 
rivers"    (1857),  directed   his  arguments  against  the  prevailing 
belief  of  the  time  that  valleys  were  carved  by  marine  currents,  I 
but  does  not  seem  to  have  considered  the  possibility  of  producing 
plains  by  the  long-continued  weathering  and  washing  of  the  land. 

The  important  paper  by  Jukes,  on  the  "  Formation  of  ...  River 
Valleys  in  the  South  of  Ireland,"  still  finds  many  followers  among 
English  geologists.  Like  Ramsay,  Jukes  assumed  an  uplifted 
plain  of  marine  denudation  on  which  the  rivers  of  to-day  began 
their  erosive  work  (399),  but  he  did  not  specify  slow  depression 
during  the  marine  denudation. 

Lyell  said  little  on  the  problem  before  us.  His  "Principles" 
do  not  discuss  plains  of  denudation.  His  "  Elements  of  Geology" 
allow  only  small  valleys  to  stream  work,  and  ascribe  the  larger 
valleys  "to  other  causes  besides  the  mere  excavating  power  of 
rivers"  (70).  It  is  said  that  "denudation  has  had  a  leveling  influ- 
ence on  some  countries  of  shattered  and  disturbed  strata"  (71). 
Again,  "in  the  same  manner  as  a  mountain  mass  may,  in  the 
course  of  ages,  be  formed  by  sedimentary  deposition,  layer  after 
layer,  so  masses  equally  voluminous  may  in  time  waste  away  by 
inches  ;  as,  for  example,  if  beds  of  incoherent  materials  are  raised 
slowly  in  an  open  sea  where  a  strong  current  prevails"  (70). 
The  problem  of  sub-aerial  denudation  here  discussed  was  not 
then  formulated. 

The  writings  of  Sir  A.  Geikie  offer  several  interesting  quota- 
tions. When  describing  the  general  uniformity  of  the  sky  line 
over  the  Scotch  Highlands  in  the  first  edition  (1865)  of  the 
"  Scenery  of  Scotland,"  he  writes : 

In  other  words,  these  mountain  tops  are  parts  of  a  great  undulating  plain 
or  table-land  of  marine  denudation.  .  .  .  The  marine  denudation  probably 
went  on  during  many  oscillations  of  level,  and  the  general  result  would 
hence  be  the  production  of  a  great  table-land,  some  parts  rising  gently  to 
a  height  of  many  hundred  feet  above  other  portions,  yet  the  whole  wearing 
that  general  tameness  and  uniformity  of  surface  characteristic  of  a  table- 
land where  there  are  neither  any  conspicuous  hills  towering  sharply  above 
the  average  level  nor  any  valleys  sinking  abruptly  below  it.  ...  The  valleys 


326  PHYSIOGRAPHIC  ESSAYS 

which  now  intersect  it  ...  have  probably  been  dug  out  of  it  by  the 
agencies  of  denudation.  If,  therefore,  it  were  possible  to  replace  the  rock 
which  has  been  removed  in  the  excavation  of  these  hollows,  the  Highlands 
would  be  turned  into  a  wide,  undulating  table-land,  sloping  up  here  and 
there  into  long,  central  heights  and  stretching  out  between  them  league  after 
league  with  a  tolerable  uniformity  of  level.  And  in  this  rolling  plain  we 
should  find  a  restoration  of  a  very  ancient  sea  (a,  106,  108). 

On  earlier  pages  sub-aerial  agents  are  described  as  producing 
valleys  and  cliffs,  while  the  sea,  aided  by  the  atmosphere,  pro- 
duces a  plain  of  marine  denudation. 

An  essay,  "  On  Modern  Denudation,"  by  the  same  author,  rec- 
ognizes that  plains  of  denudation  are  reduced  mainly  by  sub-aerial 
forces,  but  concludes  that  "undoubtedly  the  last  touches  in  the 
long  processes  of  sculpturing  were  given  by  waves  and  currents, 
and  the  surface  of  the  plain  corresponds  with  the  lower  limit  of 
the  action  of  these  forces"  (b,  186). 

In  the  second  edition  (1887)  of  his  delightful  book  on  the 
"Scenery  of  Scotland,"  argument  is  still  directed  against  the 
prejudice  that  mountains  are  due  to  local  upheaval ;  in  a  word, 
against  the  prepossession  that  mountainous  districts,  like  the 
Scotch  Highlands,  are  constructional  .forms  not  significantly 
modified  by  denudation ;  but  greater  value  is  given  to  sub-aerial 
agencies  than  before : 

The  more  we  consider  the  present  operations  of  sub-aerial  denuding 
agents,  the  more  we  shall  be  convinced  that  a  system  of  hills  and  valleys, 
with  all  the  local  varieties  of  scenic  feature  that  now  diversify  the  surface 
of  the  earth,  may  be  entirely  produced  by  denudation,  without  further  help 
from  underground  forces  than  the  initial  uplift  into  land.  No  matter  what 
may  be  the  original  configuration  of  the  mass  of  land,  the  flow  of  water 
across  its  surface  will  inevitably  carve  out  a  system  of  valleys  and  leave 
ridges  and  hills  between  them  (d,  94). 

The  possibility  of  producing  a  plain  by  a  continuance  of  this 
process  is  not  here  alluded  to,  but  on  an  earlier  page  the  aid  of 
shore  waves  is  called  on : 

The  limit  beneath  which  there  is  little  effective  erosion  by  waves  and 
tidal  currents  probably  does  not  exceed  a  very  few  hundred  feet.  Worn 
down  to  that  limit,  the  degraded  land  would  become  a  submarine  plain, 
across  the  surface  of  which  younger  deposits  might  afterward  be 
strewn  (d,  92). 


MARINE  AND  SUB-AERIAL  DENUDATION          327 

On  later  pages  the  author  continues : 

The  table-land  of  the  Highlands  has  been  the  work  not  of  subterranean 
action  but  of  superficial  waste.  The  long,  flat  surfaces  of  the  Highland 
ridges,  cut  across  the  edges  of  the  vertical  strata,  mark,  I  believe,  fragments 
of  a  former  base-level  of  erosion.  In  other  words,  they  represent  the  gen- 
eral submarine  level  to  which  the  Highland  region  was  reduced  after  pro- 
tracted exposure  to  sub-aerial  and  marine  denudation.  The  valleys  which 
now  intersect  the  table-land  .  .  .  have  been  eroded  out  of  it.  If,  therefore, 
it  were  possible  to  replace  the  rock  which  has  been  removed  in  the  excava- 
tion of  these  hollows,  the  Highlands  would  be  turned  into  a  wide,  undulat- 
ing table-land  ;  .  .  .  and  in  this  rolling  plain  we  should  find  a  restoration  of 
the  bottom  of  a  very  ancient  sea.  ...  Its  mountains  were  leveled  ;  its  val- 
leys were  planed  down ;  and  finally  the  region  was  reduced  to  a  base-level 
of  erosion  beneath  the  waves.  .  .  .  Some  central  tracts  of  higher  ground 
.may  have  been  left  as  islands  (</,  137,  138). 

In  Geikie's  "Text-Book  of  Geology"  sub-aerial  denudation  is 
regarded  as  providing  a  greater  amount  of  detritus  than  marine 
denudation,  and  a  significant  modification  is  made  of  Ramsay's 
interpretation  of  plains  of  marine  denudation.  In  the  actual  pro- 
duction of  such  plains 

the  sea  has  really  had  less  to  do  than  the  meteoric  agents.  A  "plain  of 
marine  denudation  "  is  that  sea-level  to  which  a  mass  of  land  had  been 
reduced  mainly  by  the  sub-aerial  forces,  the  line  below  which  further  degra- 
dation became  impossible,  because  the  land  was  thereafter  protected  by 
being  covered  by  the  sea.  Undoubtedly  the  last  touches  in  the  long  process 
of  sculpturing  were  given  by  marine  waves  and  currents,  and  the  surface 
of  the  plain,  save  where  it  has  subsided,  may  correspond  generally  with  the 
lower  limit  of  wave  action  (c,  434,  435). 

Plains  or  peneplains  of  sub-aerial  denudation,  elevated  into  a 
new  cycle  of  erosion  without  waiting  to  be  planed  off  by  the  sea, 
are  not  explicitly  considered.  Under  "  terrestrial  features  due  to 
denudation  "  it  is  stated  that 

table-lands  may  sometimes  arise  from  the  abrasion  of  hard  rocks  and  the 
production  of  a  level  plain  by  the  action  of  the  sea,  or  rather  [by]  that  action 
combined  with  the  previous  degradation  of  the  land  by  sub-aerial  waste. 
Such  a  form  of  surface  may  be  termed  a  "table-land  of  erosion"  (c,  939). 

That  an  author  who  has  so  ably  discussed  the  relative  compe- 
tence of  marine  and  sub-aerial  denudation  should  not  give  explicit 
account  of  plains  worn  down  under  the  air  and  afterward  uplifted 


328  PHYSIOGRAPHIC  ESSAYS 

and  dissected,  illustrates  how  strongly  the  doctrine  of  marine 
denudation  has  been  impressed  on  the  geologists  of  to-day.  Brief 
citation  may  be  made  from  a  number  of  other  books  and  essays. 

The  able  article,  "The  Denudation  of  the  Weald,"  in  which 
Foster  and  Topley  did  so  much  to  advance  the  modern  under- 
standing of  the  sub-aerial  origin  of  valleys,  assumed  that  the 
streams  of  southern  England  began  to  act  on  an  uplifted  plain  of 
marine  denudation,  and  from  this  arbitrary  beginning  explained 
the  transverse  valleys  by  which  the  chalk  escarpments  around  the 
Weald  are  trenched  (473). 

Maw  in  his  essay,  "  Notes  on  the  Comparative  Structure  of 
Surfaces  produced  by  Sub-aerial  and  Marine  Denudation,"  con- 
trasts hills  and  valleys  carved  by  rain  and  rivers  with  plains  of 
denudation  carved  by  the  sea. 

In  the  same  way,  Wynne  wrote  "On  Denudation  with  Refer- 
ence to  the  Configuration  of  the  Ground,"  and  concluded  that 

rain  seems  to  act  vertically,  its  tendency  always  being  to  produce  steep 
ground  where  it  is  not  accumulating  materials.  Thus  we  are  obliged,  in  the 
absence  of  anything  more  likely  to  produce  them,  to  attribute  the  formation 
of  plains  to  the  action  of  the  sea  (10). 

A  little  later  Whitaker,  when  advocating  the  origin  of  cliffs 
and  escarpments  by  sub-aerial  denudation,  said  that  nature  "  uses 
the  sea  to  carve  out  continents  and  islands  ;  rain  and  rivers  to  cut 
out  hills  and  valleys"  (454). 

Mackintosh  in  his  "Scenery  of  England  and  Wales"  (1869) 
carries  the  doctrine  of  marine  erosion  to  an  extreme  and  allows 
hardly  anything  to  sub-aerial  agencies.  Even  the  inner  Triassic 
lowlands  of  England,  inside  of  the  oolitic  escarpment,  are  ascribed 
to  marine  denudation.  "  The  sea  must  have  mainly  given  rise  to 
the  inequalities  of  the  earth's  surface,  so  far  as  they  are  the  result 
of  denudation  "  (292). 

It  appears,  therefore,  that  the  active  discussion  in  England,  of 
which  the  above  extracts  give  some  indication,  did  not  consider 
the  possibility  of  sub-aerial  base-leveling,  but  was  concerned  chiefly 
with  the  origin  of  valleys  by  rain  and  rivers.  Since  the  settlement 
of  this  question,  land  sculpture  has  not  received  much  attention 
from  English  geologists,  as  the  following  extracts  from  a  later 
period  will  show. 


MARINE  AND  SUB-AERIAL  DENUDATION          329 

Green  says,  "The  even  surface  that  would  result  from  the  action 
of  marine  denudation  is  called  a  ' plain  of  marine  denudation'" 
(577).  No  appreciable  wearing  takes  place  below  the  level  of  the 
lowest  tides.  No  mention  is  made  of  a  cover  of  sediments  as  a 
characteristic  accompaniment  of  the  plain  of  denudation,  and  no 
consideration  is  given  to  the  plains  of  sub-aerial  denudation  ; 
only  the  lesser  inequalities  of  land  form  are  ascribed  to  sub-aerial 
agencies. 

The  edition  of  "Phillips'  Manual  of  Geology,"  by  Etheridge 
and  Seeley  (1885),  briefly  describes  plains  of  marine  denudation 
(131),  and  under  sub-aerial  denudation  goes  no  further  than  to 
explain  the  origin  of  valleys. 

Woodward,  in  his  valuable  summary  of  the  "  Geology  of  Eng- 
land and  Wales,"  follows  his  predecessors  in  adopting  the  idea  of 
marine  denudation  for  the  production  of  plains. 

Jukes-Brown  writes : 

Plains  of  erosion  are  those  which  have  been  formed  by  marine  erosion 
across  the  edges  and  outcrops  of  strata  without  reference  to  their  inclina- 
tion, flexures,  or  fractures.  They  are  surfaces  of  planation  formed  by  the 
march  of  the  sea  across  the  country.  The  limestone  plains  of  central  Ire- 
land may  be  cited  as  an  instance  (620). 

Sub-aerial  agencies  are  not  considered  beyond  the  formation 
of  valleys.  For  example  :  "As  soon  as  this  surface  produced  by 
marine  erosion  is  elevated  into  dry  land,  it  is  subjected  to  the 
detritive  action  of  the  sub-aerial  agencies  already  described,  and 
is  ultimately  carved  out  into  new  forms  of  hill  and  valley  (565)." 

Detritive  and  erosive  agencies  are  grouped  under  two  heads : 

(i)  Marine  agencies,  which  act  along  the  margin  of  the  land,  and  tend 
to  produce  an  approximate  level  surface  or  plain  ;  (2)  sub-aerial  agencies, 
which  act  over  the  whole  surface  of  the  land,  and  tend  to  produce  a  system 
of  valleys  and  watersheds,  hollows  and  relative  eminences  (564), 

In  discussing  breaches  in  the  escarpments  and  hill  ranges  of  the 
Wealden  district,  the  same  author  says : 

The  only  explanation  of  these  facts  is  ...  marine  erosion  first  produced 
a  surface  of  planation  across  the  whole  district  while  it  was  being  slowly 
elevated,  so  that  this  original  surface  sloped  gently  from  a  central  line  to- 
ward the  north  and  south.  The  primary  streams  naturally  followed  these 
slopes,  .  .  .  forming  the  transverse  valleys  (581). 


330  PHYSIOGRAPHIC  ESSAYS 

Among  continental  geologists  Richthofen  is  the  leading  advo- 
cate of  marine  erosion.  He  treated  the  origin  of  plains  of  denu- 
dation, independently  of  Ramsay's  writings,  in  his  great  work  on 
China,  attention  being  led  to  the  problem  by  the  occurrence  of 
unconformable  marine  strata  lying  on  smooth  foundations,  as  ob- 
served in  his  eastern  travels.  He  concludes  that  the  "oldland" 
platform  cannot  have  been  produced  by  atmospheric  wasting  or 
by  running  water ;  these  agencies  produce  valleys  separated  by 
ridges.  Truly,  the  valleys  multiply  and  widen  and  the  ridges 
weaken,  but  reduction  to  a  lowland  can  be  reached  only  locally 
and  in  small  dimensions.  Moreover,  change  in  the  altitude  of  land 
works  against  complete  denudation ;  yet,  although  such  a  result 
is  unattainable  by  sub-aerial  agencies,  it  may  be  accomplished  by 
the  waves  of  the  sea  beating  on  the  coast.  Three  cases  are  con- 
sidered :  a  stillstand  of  the  land  for  an  indefinite  period,  a  slow 
elevation,  and  a  slow  depression.  The  stillstanding  land  would 
be  cut  inward  to  a  limited  distance,  after  which  the  waves  would 
be  exhausted  on  the  platform  of  their  own  carving.  During  ele- 
vation slight  effect  could  result,  for  the  work  would  always  be 
beginning  anew.  Slow  depression  alone  can  produce  regional 
abrasion,  for  then  the  power  of  the  waves  is  maintained  by  the 
continued  sinking  of  the  bottom,  while  detritus  accumulates  on 
it.  In  contrast  to  structural  plateaus  (Sckicktungsplateaus),  pla- 
teaus of  denudation  have  no  relation  to  the  structures  across 
which  they  are  cut  or  to  the  valleys  which  are  sunk  beneath 
their  level  after  general  elevation.  As  examples,  the  Ardennes 
and  the  uplands  of  the  middle  Rhine  are  first  mentioned,  these 
being  explained  as  producible  only  by  sea  waves,  never  by  flow- 
ing water  or  other  sub-aerial  agents.  Another  example  given  is 
the  western  slope  of  the  Sierra  Nevada  of  California,  now  uplifted 
and  dissected  (a). 

The  substance  of  the  above  is  repeated  in  Richthofen's  "  Fuh- 
rer  fur  Forschungsreisende "  (b,  353-361),  emphasis  being  given 
to  the  association  of  plains  of  denudation  with  unconformably 
overlying  sediments,  to  which  the  English  school  directs  insuf- 
ficient attention.  Sub-aerial  agents  are  described  as  excavating 
valleys  in  uplifted  plains  of  denudation,  but  not  in  producing  the 
plains  (b,  171-173,  670,  671).  The  prevalence  of  superposed 


MARINE  AND  SUB-AERIAL  DENUDATION  331 

streams  in  certain  dissected  uplands  of  abrasion  js  noted  (by  671, 
672),  but  no  contrast  drawn  between  these  examples  and  others 
in  which  the  streams  are  systematically  adjusted  to  the  structures. 

Cornet  and  Briart  have  made  special  study  of  the  greatly  de- 
formed Paleozoic  rocks  of  Belgium,  which  they  believe  once  rose 
in  lofty  mountains.  Although  they  regard  sub-aerial  agencies 
competent  to  produce  the  "  complete  ablation  "  of  a  land  surface, 
they  conclude  that  it  was  probably  the  waves  of  an  encroaching 
sea  that  contributed  largely  to  destroy  what  remained  of  their 
ancient  mountains  in  Cretaceous  time  (72-113). 

Philippson  follows  Richthofen  in  treating  plains  of  denudation 
—  abrasionsflachen  —  as  the  result  of  wave  action  (100). 

The  American  School.  Few  American  writers  accept  the  belief 
of  the  English  school.  The  first  clear  recognition  of  the  impor- 
tance of  sub-aerial  base-leveling  should,  I  believe,  be  credited  to 
our  geologists  in  the  western  surveys.  Marvine  briefly  presented 
the  essence  of  the  idea  in  1873,  but  he  made  mention  of  marine 
action  in  a  late  stage  of  the  process,  somewhat  after  the  fashion 
of  the  English  school.  Describing  the  east  slope  of  the  Rocky 
Mountain  front  range,  he  wrote  : 

The  ancient  erosion  gradually  wore  down  the  mass  of  Archean  rocks  to 
the  surface  of  the  sea,  .  .  .  the  mass  was  finally  leveled  off  irrespective  of 
structure  or  relative  hardnesses  of  its  beds,  by  the  encroaching  ocean,  which 
worked  over  its  ruins  and  laid  them  down  upon  the  smoothed  surface  in  the 
form  of  the  Triassic  and  other  beds  (144). 

Powell's  "  Exploration  of  the  Colorado  River"  (1875)  brought 
the  American  view  of  the  capabilities  of  sub-aerial  erosion  more 
prominently  forward,  yet  the  text  does  not  furnish  brief  explicit 
statement  directly  to  the  effect  that  lowlands  of  denudation  may 
be  produced  by  sub-aerial  agencies.  Extracts  would  lose  their 
flavor  apart  from  their  context,  but  in  figuring  a  section  of  the 
wall  in  the  Grand  Canon  the  beveled  surface  of  the  tilted  older 
strata  on  which  the  horizontal  Carboniferous  strata  lie  is  drawn 
smooth  and  even.  The  overlying  beds  "are  records  of  the  inva- 
sion of  the  sea ;  the  line  of  separation  the  record  of  a  long  time 
when  the  region  was  dry  land"  (a,  212).  Here  the  implication  is 
that  the  sea  gained  entrance  by  depression  of  the  base-leveled 
land.  The  overlying  strata  are  regarded  as  the  ruins  of  some 


332  PHYSIOGRAPHIC  ESSAYS 

unrepresented  land,  not  of  the  locally  buried  land.  The  expla- 
nation is  precisely  opposite  to  that  given  to  similar  structures 
by  Richthofen. 

In  Powell's  "Geology  of  the  Uinta  Mountains"  (1876)  there 
is  a  similar  absence  of  explicit  account  of  base-leveled  plains, 
apparently  because  it  was  not  necessary  to  expand  truisms  so 
simple  ;  but  the  chapter  on  degradation  very  clearly  implies  the 
capacity  of  sub-aerial  forces  to  wear  down  mountains,  however 
high  ;  indeed,  its  burden  is  to  show  that  the  destruction  of  a 
lofty  range  is  so  much  accelerated  by  steep  declivity  that  its  life 
cannot  be  much  longer  than  that  of  a  low  range.  Mountains  are 
"ephemeral  topographic  forms  ";  all  existing  mountains  are  geo- 
logically recent  (b,  197).  All  this  without  once  calling  on  the  aid 
of  sea  waves. 

Button's  monograph  on  the  "Tertiary  History  of  the  Grand 
Canon  District"  (1882)  is  most  characteristically  American  in 
treatment  as  in  theme.  Referring  to  the  great  unconformity 
near  the  base  of  the  canon  walls  in  the  Kaibab  and  Sheavwits 
plateaus,  he  says:  "The  horizontal  Carboniferous  beds  appear 
to  have  been  laid  down  upon  the  surface  of  a  country  which  had 
been  enormously  eroded  and  afterward  submerged  "  (207). 

The  erosion  followed  uplift,  the  deposition  followed  submer- 
gence when  the  erosion  was  essentially  completed.  Along  the 
surface  of  contact  there  are 

a  few  bosses  of  Silurian  strata  rising  higher  than  the  hard  quartzitic  sand- 
stone which  forms  the  base  of  the  Carboniferous.  These  are  Paleozoic  hills, 
which  were  buried  by  the  growing  mass  of  sediment.  But  they  are  of  insig- 
nificant mass,  rarely  exceeding  two  or  three  hundred  feet  in  height,  and  do 
not  appear  to  have  ruffled  the  parallelism  of  the  sandstones  and  limestones 
of  the  massive  Red  Wall  group  above  them  (209). 

On  another  page  Button  says  : 

The  meaning  of  this  great  unconformity  obviously  is  that  after  a  vast 
body  of  early  Paleozoic  strata  had  been  laid  down  they  were  distorted  by 
differential  vertical  movements,  were  flexed  and  faulted,  and  were  elevated 
above  the  sea.  They  were  then  enormously  eroded.  .  .  .  Still  later  the 
region  was  again  submerged  (181). 

Over  the  rugged  country  thus  ravaged,  the  later  strata,  perhaps 
fifteen  thousand  feet  thick,  were  laid  down. 


MARINE  AND  SUB-AERIAL  DENUDATION  333 

Many  other  examples  of  the  American  view  may  be  given. 
Most  of  them,  as  in  the  cases  already  cited,  take  no  account  of 
the  possibility  that  the  evenly  abraded  surface  of  the  older  ter- 
rane  might  be  essentially  the  product  of  wave  work,  but  tacitly 
assume  that  it  resulted  from  sub-aerial  erosion,  followed  by  de- 
pression, with  more  or  less  tilting,  so  that  the  submerged  area 
comes  to  be  sheeted  over  with  waste  derived  from  some  non- 
submerged  area. 

Irving  concludes  that  in  Wisconsin  "an  amount  of  material 
vast  beyond  computation  was  removed  from  this  ancient  land 
before  the  encroachment  upon  it  of  the  sea  within  which  the 
[Potsdam]  sandstone  was  deposited  "  (402). 

The  buried  oldland  is  referred  to  as  a  "  sub-Potsdam  land  sur- 
face "  (409). 

Van  Hise,  writing  of  the  great  unconformities  below  and  above 
the  Penokee  series  of  Wisconsin  and  upper  Michigan,  implies 
great  sub-aerial  erosion,  by  which  an  uplifted  region  was  reduced 
to  a  peneplain  ;  depression,  submergence,  and  deposition  of  ma- 
terial eroded  elsewhere  then  followed.  The  essentials  of  the 
explanation  are  that  the  Penokee  series  rests  upon  an  ancient 
land  surface,  more  or  less  modified  by  wave  action  at  the  time  of 
submergence,  but  worn  down  from  its  constructional  form  almost 
entirely  by  sub-aerial* agents  (454-466). 

Walcott,  recognizing  wave  work  at  the  margin  of  an  encroach- 
ing sea  as  contributing  to  the  formation  of  basal  conglomerates, 
nevertheless  explains  the  great  pre-Cambrian  land  area  of  our 
country  as  "approaching  the  base-level  of  erosion  over  large 
portions  of  its  surface"  (562).  Moreover,  it  was  a  result  of  conti- 
nental depression  and  not  of  erosive  encroachment  of  the  waves 
that  the  upper  Cambrian  sea  gained  its  extension  over  the  great 
interior  of  the  continent  (565).  The  relation  of  sub-aerial  and 
marine  agencies  are  here,  as  in  so  many  instances,  just  reversed 
from  their  proportionate  activities  in  Richthofen's  scheme. 

McGee  was  the  first  to  present  a  clear  statement  of  the  vast 
sub-aerial  denudation  of  our  Atlantic  slope  in  Mesozoic  time : 

Before  the  initiation  of  Potomac  deposition,  but  subsequent  to  the  ac- 
cumulation of  the  Triassic  and  Rhaetic  deposits  and  to  the  displacement 
and  diking  by  which  they  are  affected,  there  was  an  eon  of  degradation 


334  PHYSIOGRAPHIC  ESSAYS 

during  which  a  grand  mountain  system  was  obliterated  and  its  base  re- 
duced to  a  plain  which,  as  its  topography  tells  us,  was  slightly  inclined 
seaward  and  little  elevated  above  tide.  .  .  .  There  followed  a  slight  eleva- 
tion of  the  land,  when  the  rivers  attacked  their  beds  and  excavated  valleys 
as  deep  as  those  to-day  intersecting  the  Piedmont  plain.  .  .  .  Then  came 
the  movement  by  which  the  deposition  of  the  Potomac  formation  was  initi- 
ated ;  the  deeply  ravined  base-level  plain  was  at  the  same  time  submerged 
and  tilted  oceanward  (142). 

It  appears  from  the  foregoing  examples  that  in  denuded  plains 
over  which  unconformable  sediments  have  been  deposited,  some 
small  share  in  the  work  of  denudation  may  be  allowed  to  the 
shore-waves  as  they  advance  over  an  already  prepared  peneplain  ; 
but  it  is  otherwise  with  those  uplifted  and  dissected  plains  of 
denudation  upon  which  there  is  no  reason  to  think  that  uncon- 
formable sediments  have  ever  been  deposited.  The  plateau  in 
which  the  Grand  Canon  of  the  Colorado  is  cut  is  an  extraordinary 
example  of  this  kind.  It  is,  moreover,  notable  for  consisting  of 
nearly  horizontal  strata,  where  acute  observation  has  been  needed 
to  detect  evidence  of  the  long  cycle  of  erosion  passed  through 
before  the  region  was  uplifted  to  its  present  altitude. 

The  great  plateau  is  beveled  obliquely  across  the  Carboniferous 
and  Permian  strata,  so  that  the  undulating  surface  of  the  upland 
in  its  medial  part  presents  Permian  beds  on  the  hills  and  Carbo- 
niferous beds  in  the  hollows ;  but  to  the  south,  where  the  strata 
gently  rise,  the  whole  surface  is  Carboniferous ;  to  the  north, 
where  the  strata  sink,  the  surface  is  entirely  Permian. 

We  may  suppose  that  this  entire  region,  at  the  epoch  at  which  the  great 
denudation  of  the  Mesozoic  system  approached  completion,  occupied  a 
level  not  much  above  the  sea.  Under  such  circumstances  it  would  have 
been  at  what  Powell  terms  base-level  of  erosion.  The  rivers  and  tributaries 
would  no  longer  corrade  their  channels.  The  inequalities  which  are  due  to 
land  sculpture  and  the  general  process  of  erosion  would  then  no  longer  in- 
crease, and  the  total  energy  of  erosion  would  be  occupied  in  reducing  such 
inequalities  as  had  been  previously  generated.  During  peripds  of  upheaval, 
and  for  a  considerable  time  thereafter,  the  streams  are  cutting  down  their 
channels,  and  weathering  widens  them  into  broad  valleys  with  ridges  be- 
tween. The  diversification  so  produced  reaches  a  maximum  when  the 
streams  have  nearly  reached  their  base-levels  ;  but  when  the  streams  can  no 
longer  corrade,  and  if  the  uplifting  ceases,  these  diversifications  are  reduced 
and  finally  obliterated.  Such,  I  conceive,  was  the  case  here.  .  .  .  The  entire 
region  was 'planed  down  to  a  comparatively  smooth  surface  (Button,  119). 


MARINE  AND  SUB-AERIAL  DENUDATION          335 

Willis  first  called  attention  to  the  occurrence  of  an  uplifted  and 
dissected  peneplain  of  sub-aerial  denudation  in  the  mountains  of 
North  Carolina  (a,  297),  and  Hayes  and  Campbell  have  since 
then  shown  the  great  extent  and  area  of  this  ancient  land  surface 
(69).  Willis  and  Hayes  have  described  the  northern  and  southern 
Appalachians,  giving  much  attention  to  the  essential  extinction 
of  the  mountains,  except  in  the  Carolina  highlands,  in  late 
Cretaceous  time.  The  first  author  writes  of  the  lowland  thus 
produced :  "  The  land  was  flat,  featureless,  and  very  slightly  ele- 
vated above  the  sea  "  (b,  189).  The  second  author  writes :  "  The 
whole  region  was  reduced  to  a  nearly  featureless  plain,  relieved 
only  by  a  few  groups  of  monadnocks  where  the  highest  moun- 
tains now  stand  "  (a,  330). 

Emerson  writes  of  the  Berkshire  hills  in  western  Massachusetts: 

Erosion  planed  away  the  mountains  to  the  general  level,  which  can  still 
be  seen  in  the  average  level  of  the  plateau,  pitching  slightly  east.  .  .  . 
When  this  peneplain  was  formed  it  was  doubtless  horizontal  and  near  the 
sea-level,  and  was  what  is  called  a  base-level. 

Salisbury  says  that  the  even  crest  lines  of  the  New  Jersey 
highlands  tell  of  "  mountainous  elevations  reduced  to  a  peneplain 
near  the  level  of  the  sea  (8)." 

Not  only  the  tilted  rocks  of  the  Alleghenies  and  of  the  older 
Appalachian  belt,  but  the  horizontal  strata  of  the  Allegheny 
plateau  are  regarded  as  having  been  base-leveled,  or  almost  so, 
before  their  present  uplift  and  dissection  was  gained.  See,  for 
example,  the  account  of  the  Cumberland  plateau  in  Tennessee 
by  Hayes  (b). 

Griswold  has  recognized  a  greatly  dissected  peneplain  in  the 
even-crested  ridges  of  the  Arkansas  novaculites,  and  has  associa- 
ted the  warping  of  the  great  peneplain  of  which  his  special  district 
was  a  part  with  the  origin  of  the  lower  course  of  the  Mississippi 
in  late  Mesozoic  time  (a,  b). 

Keyes  and  Hershey  have  recently  described  the  upland  of  the 
Ozark  plateau  in  Missouri  as  an  uplifted  and  dissected  peneplain. 
The  region  has  an  essentially  horizontal  structure,  like  the  Alle- 
gheny plateau,  with  which  it  is  in  many  ways  homologous.  The 
latter  author  tells  of  residual  hills  or  monadnocks  which  still  sur- 
mount the  upland  plain,  and  of  faint  inequalities  of  form  that 


336  PHYSIOGRAPHIC  ESSAYS 

seem  to  mark  "  the  hydrographic  basins  of  the  streams  which 
flowed  on  the  Cretaceous  lowland  plain";  but  as  a  whole  the 
region  was  "a  low,  marshy  plain  of  very  slight  relief,  probably 
nearly  at  sea-level"  (338). 

Darton  describes  the  Piedmont  area  of  Virginia  as 

an  undulating  plateau  carved  in  greater  part  in  crystalline  rocks  .  .  .  trav- 
ersed by  rivers  which  flow  in  gorges.  ...  It  is  now  very  clearly  recognized 
that  the  Piedmont  plateau  is  a  peneplain  of  Tertiary  age.  .  .  There  is 
a  system  of  very  low,  flat  divides  coincident  with  those  of  the  present  drain- 
age system  (568-570). 

Keith  also  describes  the  formerly  even  surface  of  the  Piedmont 
belt  in  which  the  valleys  of  to-day  are  incised,  as  a  Tertiary  base- 
level  of  sub-aerial  origin  (369). 

The  beveled  western  slope  of  the  Sierra  Nevada,  regarded  as 
an  upturned  plain  of  marine  abrasion  by  Richthofen,  is  ascribed 
by  Gilbert,  Leconte,  Lindgren,  Diller,  and  others  to  sub-aerial 
denudation ;  but  Lindgren  makes  it  clear  that  when  the  region 
stood  lower  it  was  not  worn  smooth  enough  to  be  called  a  pene- 
plain ;  "  the  declivities  and  irregularities  of  the  old  surface  are  too 
considerable  for  that"  (298). 

Diller  describes  a  peneplain  formed  on  the  upturned  Creta- 
ceous rocks  of  northern  California  and  now  dissected  by  various 
streams : 

The  production  of  such  a  broad,  uniform  plain  by  the  erosion  of  rocks 
varying  greatly  irt  hardness  could  only  be  accomplished  on  a  very  gentle 
slope  near  the  level  of  the  controlling  water  body,  and  we  may  therefore 
properly  consider  this  plain  a  base-level  of  erosion  (<£,  405). 

Lawson  presents  an  instructive  account  of  an  uplifted  and 
dissected  peneplain  beveled  across  upturned  strata  in  northern 
California.  Waterworn  gravels  occur  on  the  ridges  of  the  dis- 
sected upland.  They  "can  only  be  interpreted  as  remnants  of 
the  stream  gravels  of  the  ancient  peneplain"  (244). 

G.  M.  Dawson  describes  an  ancient  peneplain,  now  an  elevated 
and  dissected  plateau,  in  the  Rocky  mountain  region  of  Canada : 

Climbing  to  the  level  of  this  old  plateau,  or  to  that  of  some  slightly 
more  elevated  point  about  the  fiftieth  or  fifty-first  parallel  of  latitude,  the 
deep  valleys  of  modern  rivers  with  other  low  tracts  are  lost  sight  of,  and 


MARINE  AND  SUB-AERIAL  DENUDATION  337 

the  eye  appears  to  range  across  an  unbroken  or  but  slightly  diversified 
plain,  which,  on  a  clear  day,  may  be  observed  to  be  bounded  to  the  north- 
east, southwest,  and  south  by  mountain  ranges  with  rugged  forms,  and 
above  which  in  a  few  places  isolated  higher  points  rise,  either  as  outstand- 
ing monuments  of  the  denudation  by  which  tne  plateau  was  produced,  or 
as  accumulations  due  to  volcanic  action  of  the  Miocene  or  middle  Tertiary 
period  (i  i). 

After  explicitly  considering  the  alternatives  of  marine  and  sub- 
aerial  erosion,  the  author  decides  against  the  former,  because  the 
plateau  district  is  not  accessible  to  the  sea,  and  because  there  are 
no  marine  strata  thereabouts  referable  to  the  period  when  the 
peneplain  was  formed.  The  river  system  of  the  region, 

aided  by  other  sub-aerial  agencies,  cut  down  almost  its  entire  drainage  basin 
till  this  became  a  nearly  uniform  plain,  with  some  slight  slope  in  the  main 
direction  of  the  river's  flow,  but  of  which  the  lowest  part  approximately 
coincided  with  the  sea-level  of  the  time.  .  .  .  After  reaching  this  base-level 
of  erosion  the  rivers  would,  of  course,  be  unable  to  do  more  than  serve  as 
channels  for  the  conveyance  of  material  brought  into  them  from  the  sur- 
rounding country,  which,  wherever  it  stood  above  the  general  level,  was 
still  subject  to  waste.  The  valleys  became  wide  and  shallow,  and  the  sur- 
face as  a  whole  assumed  permanent  characters  (13). 

My  own  studies  lead  me  to  believe  that  sub-aerial  denudation 
has  reduced  various  mountainous  or  plateau-like  uplifts  to  low- 
land peneplains. 

A  considerable  number  of  extracts  might  be  presented  from  the 
works  of  foreign  writers  to  show  that  the  idea  of  marine  den- 
udation is  on  the  whole  less  favorably  received  by  continental 
than  by  English  geologists  ;  but  the  features  of  land  form  and 
the  processes  of  land  sculpture  have  not  been  studied  in  Europe 
with  the  attention  that  has  been  given  to  stratigraphic  succession 
or  to  the  problems  of  paleontology  and  petrography.  Regions 
that  are  known  to  be  uplands  of  denudation  are  often  described 
with  abundant  detail  as  to  their  structure,  but  with  the  scantiest 
reference  to  the  conditions  of  their  topographical  development. 

A  characteristic  example  of  this  manner  of  treatment  is  found 
in  the  valuable  works  by  Lepsius  on  the  mountains  of  the  upper 
and  middle  Rhine,  in  which  the  Schiefergebirge  and  other  ancient 
mountains  are  fully  treated  as  to  structure,  although  little  is  said 
of  their  form  and  still  less  of  the  origin  of  their  form  (a,  b). 


338  PHYSIOGRAPHIC  ESSAYS 

The  following  citations  are  from  works  in  which  land  form  and 
sculpture  are  more  fully  considered. 

The  increasing  importance  attributed  by  Sir  A.  Geikie  to  sub- 
aerial  agencies  in  his  later  writings  has  already  been  noted.  Pro- 
fessor James  Geikie  goes  farther  in  this  direction  and  says : 

Valleys  continue  to  be  deepened  and  widened,  while  the  intervening 
mountains,  eaten  into  by  the  rivers  and  their  countless  feeders  and  shattered 
and  pulverized  by  springs  and  frosts,  are  gradually  narrowed,  interrupted, 
and  reduced  until  eventually  what  was  formerly  a  great  mountain  chain 
becomes  converted  into  a  low-lying  undulating  plain  (160). 

Gosselet,  in  his  comprehensive  monograph  on  the  Ardennes, 
says  that  the  tilted,  folded,  and  faulted  strata  of  their  uplands 
have  been,  as  it  were,  planed  down  by  the  combined  action  of 
atmospheric  disintegration  and  pluvial  wearing.  Both  the  Jurassic 
and  Cretaceous  formations  are  described  as  lying  on  oldland  soils, 
where  they  overlap  the  Paleozoic  strata  (802,  808,  837). 

The  elaborate  treatise  on  "  Les  Formes  du  Terrain"  (1888), 
by  De  la  Noe  and  de  Margerie,  clearly  maintains  that  pluvial 
denudation  may  not  only  produce  valleys,  but  it  may  wear  down 
the  divides  between  the  valleys  (106).  The  escarpments  or  cross 
valleys  of  the  Weald  in  southern  England  may  be  explained  with- 
out calling  on  marine  erosion,  as  most  of  the  English  geologists 
have  done  (135,  136).  Plateaus  of  abrasion,  without  a  cover  of 
unconformable  strata,  may  be  "  simply  the  result  of  prolonged 
sub-aerial  erosion."  If  unconformably  covered,  it  still  remains  to 
be  seen  how  far  the  abraded  surface  is 

the  modification  by  wave  action  of  a  hardly  different  surface,  produced 
by  the  prolonged  work  of  streams  which  had  long  before  attained  faintly 
graded  slopes,  and  which  had  by  the  aid  of  atmospheric  agents  almost 
completely  destroyed  preexisting  inequalities  of  form  (188). 

Penck  concludes  that  the  final  aim  of  sub-aerial  denuding  agents 
is  to  reduce  a  land  almost  completely  to  a  plain  (a),  but  his  ac- 
count of  the  Schiefergebirge  of  the  middle  Rhine  does  not  ex- 
plicitly state  whether  the  abrasionsplateau  of  their  uplands  is  of 
marine  or  sub-aerial  origin  (b).  In  his  compendious  volumes  on 
the  "  Morphologic  der  Erdoberflache  "  (1894),  he  considers  plains 
of  marine  and  of  sub-aerial  denudation,  both  as  to  process  of 


MARINE  AND  SUB-AERIAL  DENUDATION          339 

origin  and  as  to  derivative  forms,  after  elevation  and  dissection, 
but  criteria  for  their  discrimination  are  not  discussed  (c). 

De  Lapparent,  president  of  the  French  Geographical  Society, 
has  advocated  sub-aerial  erosion  as  the  means  of  denuding  the 
Ardennes  and  the  central  plateau  of  France  (<z),  and  later  says: 

La  notion  des  pdndplaines  est  extremement  feconde,  et  ce  n'est  pas  un  de 
ses  moindres  me'rites  d'avoir  porte*  le  coup  de  grace  a  la  theorie  des  plaines 
de  denudation  marine,  si  fort  en  honneur  de  Fautre  cote  du  detroit  (£). 

Comparison  of  the  Two  Schools.  It  is  noteworthy  that,  with 
few  exceptions,  the  more  recent  writers  here  quoted  do  not  dis- 
cuss both  processes  by  which  smoothly  abraded  plains,  whether 
buried  or  bare,  may  be  produced,  but  directly  announce  their  con- 
clusion as  to  the  origin  —  by  marine  or  by  sub-aerial  agencies  — 
of  the  surface  under  consideration.  This,  of  course,  implies  that 
they  regard  the  question  as  settled,  just  as  for  some  time  back  it 
has  been  the  habit  of  geologists  on  finding  marine  shells  in  strati- 
fied rocks  to  conclude,  without  reviving  the  discussions  of  earlier 
centuries,  that  the  strata  are  of  marine  origin,  and  that  their  pres- 
ent position  indicates  a  change  in  the  relative  attitude  of  the  land 
and  sea.  But  in  this  latter  example  all  geologists  are  to-day 
agreed,  while  in  the  problem  of  the  origin  of  plains  of  denudation 
each  writer  follows  only  the  conclusion  of  his  own  school,  not  the 
conviction  of  the  world.  //  is  chiefly  to  arouse  attention  to  this 
aspect  of  the  problem  that  tJie  present  review  is  undertaken. 

It  is  further  noteworthy  that,  with  few  exceptions,  the  authors 
who  discuss  the  matter  at  all  do  not  attempt  to  discriminate  be- 
tween the  two  possible  classes  of  denuded  surfaces  by  searching 
for  features  peculiar  to  one  or  the  other,  but  content  themselves 
with  a  priori  argument  as  to  the  possibility  of  producing  plains 
by  marine  or  sub-aerial  agencies. 

There  is,  however,  a  certain  difference  of  attitude  in  the 'two 
schools  regarding  each  other's  doctrines.  The  English  school 
hardly  considers  at  all  the  ability  of  sub-aerial  agencies  to  produce 
smooth  plains  of  denudation;  their  discussion  of  the  question  turns 
really  on  the  possible  origin  of  valleys  by  sub-aerial  agencies. 
The  American  school  does  not,  as  far  as  I  have  read,  deny  the 
ability  of  marine  agencies,  but  attributes  greater  ability,  espe- 
cially far  in  continental  interiors,  to  sub-aerial  agencies  ;  their 


340  PHYSIOGRAPHIC  ESSAYS 

discussion  of  the  question  postulates  the  sub-aerial  origin  of  ordin- 
ary valleys  as  a  matter  already  proved,  and  goes  on  from  this  to 
the  possible  ultimate  result  of  the  valley-making  processes.  Again, 
the  English  school  denies,  tacitly  or  directly,  the  probability  or 
even  the  possibility  of  a  period  of  stillstand  long  enough  for  essen- 
tially complete  sub-aerial  denudation  close  to  sea-level,  but  as- 
sumes the  possibility  of  a  period  of  stillstand  or  of  slight  depression 
continuous  and  long  enough  to  allow  the  sea  waves  to  plane  off 
the  sinking  lands.  The  American  school  tacitly  questions  the  oc- 
currence of  great  erosive  transgressions  of  the  sea  during  either 
a  stillstand  or  a  slow  depression  of  the  land,  but  admits  the  possi- 
bility of  essentially  complete  sub-aerial  denudation  to  an  average 
sea-level,  above  and  below  which  the  land  long  hovers  in  many 
minor  oscillations  before  a  new  attitude  is  assumed  by  great  de- 
pression, elevation,  or  deformation.  It  should  be  borne  in  mind 
that  the  depressed  and  buried  or  the  uplifted  and  dissected  plains 
of  denudation  whose  origin  is  in  question  are  in  no  cases  geomet- 
rical planes  ;  they  nearly  always  possess  perceptible  inequalities, 
amounting  frequently  to  two  or  three  hundred  feet ;  but  these 
measures  are  small  compared  to  the  inferred  constructional  relief 
of  earlier  date,  or  compared  to  the  deep  valleys  often  eroded  be- 
neath the  plain  if  it  has  been  uplifted.  By  whatever  process  the 
so-called  " plain  of  denudation"  was  produced,  an  explanation 
that  will  account  for  a  peneplain  of  moderate  or  slight  relief  is 
all  that  is  necessary.  Absolute  planation  is  so  rare  as  hardly  to 
need  consideration  here. 

In  no  respect  is  the  contrast  between  the  two  schools  more 
strikingly  shown  than  in  the  beliefs  concerning  the  cover  of  un- 
conformable  strata  that  lie  or  are  supposed  to  have  lain  upon  an 
oldland.  The  continental  members  of  the  English  school  gener- 
ally regard  these  strata  as  an  essential  result  of  the  process  of 
marine  denudation  during  slow  depression ;  if  such  strata  are 
absent  from  a  dissected  plateau,  their  absence  is  explained  by 
denudation  after  uplift.  The  American  school  does  not  give  the 
cover  of  unconformable  strata  an  essential  place  in  the  problem  ; 
if  present,  it  is  generally  ascribed  to  deposition  following  the 
submergence  of  a  region  already  for  the  most  part  base-leveled 
by  sub-aerial  agencies. 


MARINE  AND  SUB-AERIAL  DENUDATION  341 

Review  of  the  A  Priori  Argument.  It  may  be  noted  that  the 
value  of  marine  agencies  gained  a  high  reputation  for  effective 
work  before  sub-aerial  agencies  were  recognized  as  significantly 
affecting  the  form  of  the  land,  and  that  from  that  time  to  the 
present  the  importance  of  the  latter  agencies  has  been  steadily 
increasing  in  the  minds  of  geologists.  The  manifest  work  of  waves 
on  a  bold  coast  was  perceived  at  a  time  when  the  production  of 
valleys  by  rain  and  rivers  was  scouted.  To-day  it  is  not  so  much 
that  the  absolute  strength  of  marine  erosion  is  given  a  smaller 
value  than  heretofore,  but  that  the  relative  importance  of  sub- 
aerial  erosion  is  rated  much  higher  than  at  the  beginning  of  the 
century.  While  the  sea  works  energetically  along  a  line,  sub-aerial  j 
forces  work  gently  over  a  broad  surface.  Chiefly  for  this  reason 
Geikie  concludes  that  "before  the  sea,  advancing  at  a  rate  of  ten  feet 
a  century,  could  pare  off  more  than  a  mere  marginal  strip  of  land 
between  seventy  and  eighty  miles  in  breadth,  the  whole  land  might 
be  washed  into  the  ocean  by  atmospheric  denudation  "  (c,  432). 

A  slight  movement  of  elevation  usually  sets  the  sea  back  to 
begin  its  work  anew  on  the  seaward  side  of  its  previous  shore-  i 
line,  but  such  an  elevation  only  accelerates  the  work  of  sub-aerial  j 
denudation  all  over  the  elevated  region.  The  waves  on  the  sea- 
shore shift  their  line  of  attack  with  every  slight  vertical  move- 
ment of  the  coastal  region ;  but  the  sub-aerial  forces  over  large 
continental  areas  gain  no  notice  of  slight  movements  until  a  con- 
siderable time  after  they  have  been  accomplished,  and  hence  they 
perform  their  task  only  with  reference  to  the  average  attitude  of 
the  land.  Observers  near  a  shore-line  naturally  have  their  atten- 
tion directed  to  the  unsteadiness  of  the  land,  as  indicated  by  marks 
of  many  recent  changes  of  land-level ;  hence  they  are  perhaps 
indisposed  to  admit  that  any  land  has  ever  stood  still  —  or  oscil- 
lated slightly  above  and  below  an  average  attitude  —  long  enough 
to  be  nearly  or  quite  base-leveled  by  sub-aerial  agencies.  They 
prefer  to  think  that  the  sea  is,  in  spite  of  its  many  stops  and  starts, 
the  great  leveler  of  the  lands. 

Some  have  intimated  that  the  insular  position  of  English  ob- 
servers has  led  them  to  exaggerate  the  relative  power  of  the  sea. 
Thus  W.  T.  Blanford,  after  much  experience  in  India  and  else- 
where, as  well  as  at  home  in  England,  writes : 


342  PHYSIOGRAPHIC  ESSAYS 

It  is  not  surprising  that  the  power  of  rain  and  rivers  should  be  recog- 
nized with  difficulty  in  regions  where  their  effects  are  comparatively  so 
dwarfed  as  in  the  British  Isles,  while  the  power  of  marine  denudation  is  at 
its  maximum  from  the  enormous  coast  line  exposed  and  the  small  amount 
of  detritus  furnished  for  its  protection  by  rivers  of  small  length  and  in 
/  ^w_hich  floods  are  of  exceptional  occurrence  (158). 

But  even  this  well-practiced  observer  contended  only  for  the 
sub-aerial  origin  of  valleys,  not  of  plains  also.  On  the  other  hand, 
those  whose  studies  have  been  directed  chiefly  to  large  interior 
areas  seldom  have  occasion  to  observe  the  action  of  energetic 
shore  waves,  and  hence  are  apt  to  attribute  relatively  little  impor- 
tance to  their  work.  The  small  share  of  attention  recently  given 
by  Powell  to  shore  waves  and  coastal  forms  in  a  general  discus- 
sion of  physiographic  processes  and  features  is  perhaps  thus 
explained  (c).  The  citation  from  Dawson,  given  above,  is  an  espe- 
cially good  illustration  of  the  manner  in  which  large  continental 
surroundings  may  affect  the  opinions  of  an  observer  who,  from  cer- 
tain associations,  might  be  expected  to  follow  the  insular  school. 

Although  mature  deliberation  and  good  judgment  may  lead 
through  a  priori  argument  to  a  safe  conclusion  in  many  problems, 
the  method  is  of  difficult  application  here  on  account  of  the  great 
number  of  variable  factors  whose  appropriate  values  can  hardly  be 
determined.  It  is  probably  by  reason  of  assigning  different  val- 
ues to  variable  factors  that  the  opposite  conclusions  summarized 
above  have  been  reached. 

Statement  of  the  A  Posteriori  Argument.  In  attempting  to  de- 
cide by  arguing  from  effect  to  cause  whether  evenly  denuded 
regions  have  been  worn  down  by  sub-aerial  or  marine  agencies,  let 
•us  try  to  stand  on  a  provisional  Atlantis,  hoping  that  it  may  give 
\steady  support  long  enough  for  us  to  gain  an  unprejudiced  view  of 
the  opinions  that  are  so  generally  accepted  on  the  lands  to  the  east 
and  west.  From  this  neutral  ground  let  us  attempt  to  deduce 
from  the  essential  conditions  of  each  explanation  of  the  problem 
as  many  as  possible  of  its  essential  consequences,  and  then  con- 
front these  consequences  with  the  facts.  The  measure  of  accord- 
ance between  consequences  of  theory  and  facts  of  observation 
will  then  serve  as  a  measure  of  the  verity  of  the  theory  from 
which  the  consequences  are  derived.  No  final  decision  can  be 


w 

r 


MARINE  AND  SUB-AERIAL  DENUDATION  343 


reached  in  many  cases,  for  however  clearly  the  consequences 
may  be  deduced,  the  facts  with  which  they  should  be  compared 
are  often  beyond  the  reach  of  observation.  In  such  cases  it  is 
advisable  to  announce  indecision  as  clearly  as  decision  is  an- 
nounced in  the  others. 

As  far  as  I  have  been  able  to  carry  the  analysis  of  the  problems, 
it  is  more  difficult  to  find  positive  criteria  characteristic  of  plains 
of  marine  denudation  than  of  plains  of  sub-aerial  denudation; 
hence  I  will  take  up  the  latter  class  first.  It  should  be  remem- 
bered, however,  that  in  each  class  of  plains  both  classes  of  agencies 
may  have  some  share,  one  preponderating  over  the  other. 

Consequences  of  Sub-aerial  Denudation.  Imagine  a  region  of 
deformed  harder  and  softer  strata  raised  to  a  considerable  eleva- 
tion. Then  let  the  land  stand  essentially  still,  or  oscillate  slightly 
above  and  below  a  mean  position.  The  rivers  deepen  their  val- 
leys, the  valleys  widen  by  the  wasting  of  their  slopes,  and  the 
hills  are  slowly  consumed.  During  this  long  process  a  most  pa- 
tient and  thorough  examination  of  the  structure  is  made  by  the 
destructive  forces,  and  whatever  is  the  drainage  arrangement 
when  the  rivers  begin  to  cut  their  valleys,  a  significant  rearrange- 
ment of  many  drainage  lines  will  result  from  the  processes  of 
spontaneous  adjustment  of  streams  to  structures.  This  involves 
the  adjustment  of  many  subsequent  streams  to  the  weaker  struc- 
tures and  the  shifting  of  many  divides  to  the  stronger  structures. 
Adjustment  begins  in  the  early  stages  of  dissection,  advances  \ 
greatly  in  the  mature  stages,  and  continues  very  slowly  toward  | 
old  age,  while  the  relief  is  fading  away.  Indeed,  when  the  region 
is  well  worn  down,  some  of  the  adjustments  of  maturity  may  be 
lost  in  the  wanderings  of  decrepitude  ;  but  this  will  seldom  cause 
significant  loss  of  adjustment  except  in  the  larger  rivers.  Now, 
if  a  region  thus  base-leveled,  or  nearly  base-leveled,  is  raised  by 
broad  and  even  elevation  into  a  new  cycle  of  geographical  life,  the 
rivers  will  carry  the  adjustments  acquired  in  the  first  cycle  over 
to  the  second  cycle.  Still  further  adjustment  may  then  be  ac- 
complished. The  master  streams  will  increase  their  drainage  area 
in  such  a  way  that  the  minor  streams  will  seldom  head  behind  a 
hard  stratum.  In  a  word,  the  drainage  will  become  more  and 
more  longitudinal,  and  fewer  and  fewer  small  streams  will  persist 


344  PHYSIOGRAPHIC  ESSAYS 

in  transverse  courses.  All  this  is  so  systematic  that  I  believe  it 
safe  to  assert  that  the  advanced  adjustments  of  a  second  cycle 
may  in  many  cases  be,  distinguished  from  the  partial  adjustments 
of  a  first  cycle.  It  should  be  noted  further  that  in  the  early 
stages  of  the  second  cycle  the  residual  reliefs  of  the  first  will 
still  be  preserved  on  the  uplands,  and  that  they  will  be  system- 
atically related  to  the  streams  by  which  the  dissection  of  the 
upland  is  in  progress,  as  noted  in  the  examples  described  by 
Darton  and  Hershey. 

It  is  manifestly  impossible  to  apply  what  may  be  called  the 
river  test  to  plains  of  denudation  upon  which  a  cover  of  uncon- 
formable  sediments  is  spread ;  but  before  assuming  that  such 
buried  plains  are  of  marine  origin,  their  uppermost  portion  next 
beneath  the  cover  should  be  examined  to  see  if.  it  presents  indi- 
cations of  secular  decay  before  burial ;  and,  if  so,  a  sub-aerial 
origin  for  the  plain  may  be  argued.  Certain  aspects  of  this  divi- 
sion of  the  subject  have  been  discussed  by  Pumpelly  (211).  An- 
other matter  of  importance  is  the  character  of  the  undermost 
layers  of  the  cover.  If  these  are  fresh-water  beds  a  sub-aerial 
origin  for  the  plain  on  which  they  rest  may  be  inferred.  The 
Potomac  formation  offers  an  example  of  this  kind  (McGee,  137, 
and  Fontaine,  61). 

Consequences  of  Marine  Demidation.  Now  suppose  that  a  region 
of  disordered  structure  is  partly  worn  down  by  rain  and  rivers  and 
is  smoothly  planed  across  by  the  sea  during  a  time  of  stillstand 
or  of  gradual  depression.  The  land  waste  gained  in  the  later 
attack  will  be  spread  offshore  on  the  platform  abraded  in  the 
earlier  attack.  The  basal  strata  of  the  unconformable  cover  thus 
formed  must  indicate  their  marine  origin  and  must  be  appropri- 
ately related  in  composition  and  texture  to  their  sources  of  supply. 
The  drainage  systems  of  the  land  will  be  essentially  extinguished 
by  the  encroaching  sea.  When  the  region  rises,  with  the  cover 
of  new  sediments  lying  evenly  on  its  smoothed  back,  a  new  system 
of  original  consequent  streams  will  take  their  way  across  it.  If 
the  elevation  be  sufficient,  the  streams  will  incise  their  valleys 
through  the  cover  of  new  sediments  and  in  time  find  themselves 
superposed  on  the  "  oldland  "  beneath. ,  As  time  passes,  more  and 
more  of  the  cover  will  be  stripped  off ;  at  last  it  may  disappear 


MARINE  AND  SUB-AERIAL  DENUDATION  345 

far  and  wide,  although  the  stripped  surface  of  the  oldland  may 
still  retain  a  generally  even  sky  line  as  a  memorial  of  its  once 
even  denudation.  Now,  in  this  case,  the  rivers  by  which  the 
dissected  plateau  is  drained  will  have  at  most  only  a  very  slight 
adjustment  to  its  structure.  Their  courses  will  have  been  inher- 
ited from  the  slope  of  the  lost  cover ;  they  will  at  first  run  at 
random  across  hard  and  soft  structures  ;  a  little  later  some  ad- 
justment to  the  discovered  structures  will  be  made,  but  as  long 
as  the  even  sky  line  of  the  upland  is  recognizable,  only  the  in- 
complete adjustments  appropriate  to  the  adolescent  stage  of  denu- 
dation can  be  gained. 

Examples  of  Dissected  Uplands  witJi  Adjusted  Drainage.  This 
essay  has  already  reached  so  much  more  than  its  expected  length 
that  it  will  not  be  possible  to  give  extended  space  to  the  consider- 
ation of  specific  examples.  This  is,  however,  no  great  disadvan- 
tage, inasmuch  as  the  number  of  examples  in  which  the  problem 
has  been  considered  in  relation  to  drainage  arrangement  and  other 
discriminating  features  is  very  small.  The  various  articles  already 
referred  to  concerning  the  geographical  development  of  the  Ap- 
palachian region  treat  this  aspect  of  the  subject  with  some  care; 
to  these  may  be  added  my  paper  on  "Certain  English  Rivers,"  in 
which  it  seems  to  me  that  there  is  shown  some  ground  for  the 
consideration  of  the  alternative  to  the  usual  English  view.  Of 
the  Ardennes  it  may  be  said  briefly  that  systematic  longitudinal 
and  transverse  streams  are  well  developed  in  certain  areas,  and 
in  those  parts,  at  least,  there  does  not  appear  direct  evidence 
of  marine  transgression.  Sheets  48  and  54.  of  the  Belgian  topo- 
graphical map  (scale,  i :  40,000)  exhibit  these  features  very 
clearly.  On  the  other  hand,  the  branches  of  the  Rhine  and  the 
Moselle  in  the  Schiefergebirge  suggest  superposition  from  a  lost 
cover,  as  mapped  on  the  sheets  of  the  Karte  des  Deutschen 
Reichs  (scale,  1:100,000). 

It  is  manifest  that  many  plains  of  denudation,  now  uplifted 
and  more  or  less  dissected,  may  be  found  in  which  no  simple  test 
based  on  the  presence  of  superposed  streams  will  serve  to  settle 
the  question  of  marine  origin.  Indeed,  it  appears  to  me  a  difficult 
matter  to  adduce  any  examples  of  extensive  plains  of  denudation 
whose  origin  is  demonstrably  marine  and  to  whose  planation 


346  PHYSIOGRAPHIC  ESSAYS 

sub-aerial  agencies  have  not  contributed  the  greater  work.  A 
region  may  be  almost  reduced  to  base-level  by  sub-aerial  denuda- 
tion when  the  transgressing  sea  completes  the  work,  extinguishing 
the  adjusted  valleys  and  introducing  superposed  streams  in  the 
next  cycle  of  denudation.  A  region  well  base-leveled  under  the 
air  may  by  quick  depression  suffer  rapid  ingression  of  the  sea, 
whose  shore  waves  will,  during  depression,  nowhere  reside  long 
enough  to  perform  a  significant  amount  of  abrasion.  When  the 
region  is  thus  submerged  and  stands  again  relatively  quiet,  the 
waste  from  a  non-submerged  area,  gained  both  by  marine  and 
sub-aerial  denudation,  may  be  spread  over  the  denuded  and  de- 
pressed plain,  and  when  this  plain  is  afterwards  elevated  with  an 
unconformable  cover  that  will  induce  superposed  drainage,  all 
trace  of  former  adjustments  will  be  lost ;  yet  here  the  planation 
was  not  marine.  A  district  of  superposed  drainage  in  central 
New  Jersey,  where  the  Amboy  clays  once  spread  over  the  red 
shales  and  sandstones  of  the  Trias,  may  probably  be  taken  as  an 
example  of  this  kind.  Superposed  rivers  cannot,  therefore,  always 
be  taken  to  prove  that  the  uplands  which  they  dissect  are  uplifted 
plains  whose  denudation  was  chiefly  performed  by  the  sea. 

Regions  of  essentially  horizontal  structure  normally  have  wan- 
dering streams  ;  no  systematic  arrangement  of  drainage  is  here 
to  be  expected.  Discrimination  in  such  regions  has  seldom  been 
attempted  between  examples  of  one  cycle  of  sub-aerial  denuda- 
tion, now  adolescent  or  mature,  and  examples  of  two  cycles,  the 
first  having  reached  old  age  and  the  second  now  being  in  its  ado- 
lescence or  maturity.  The  sky  line  would  be  smooth  and  even  in 
examples  of  either  class :  in  the  first,  because  its  original  con- 
structional form  was  a  plain  ;  in  the  second,  because  it  was  planed 
down  essentially  smooth  at  the  close  of  the  cycle  preceding  the 
current  cycle.  It  is,  however,  sometimes  possible  in  regions  of 
horizontal  structure  to  recognize  the  records  of  old  age  reached 
in  a  former  cycle  by  a  slight  discordance  between  the  general  up- 
land surface  and  the  attitude  of  the  strata  ;  or  by  the  association 
of  the  region  with  an  adjacent  region  of  tilted  structure  where 
indications  of  an  earlier  cycle  of  sub-aerial  denudation  are  mani- 
fest, both  these  tests  being  applicable  in  the  Allegheny  plateau ; 
or  by  the  arrangement  of  the  faint  residual  relief  of  the  uplands, 


MARINE  AND  SUB-AERIAL  DENUDATION  347 

where  not  trenched  by  young  or  adolescent  streams,  this  test 
having  Reen  applied  in  the  Piedmont  district  of  Virginia,  in  the 
Ozark  plateau  of  Missouri,  and  in  the  Great  plains  of  eastern 
Montana.  Further  study  of  many  other  examples  is  desirable. 


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LeConte,  Joseph.    Bull.  Geol.  Sot.  Am.,  II  (1891),  327. 
Lepsius,  G.  R.  (a)  "  Die  Oberrheinische  Tiefebene  und  ihre  Randgebirge." 

Forschungen  zur  Deut.  Landeskunde,  I  (1885),  35-91. 
(b}  Geologic  von  Deutschland  (1887). 
Lindgren,  W.    Bull.  Geol.  Soc.  Am.,  IV  (1893),  298. 
Lyell,  Sir  Charles.     Elements  of  Geology.    6th  ed.,  1868. 
Marvine,  A.  R.    Haydetfs  Survey  (Report  for  1873),  X44- 
Maw,  G.    "  Notes  on  the  Comparative  Structure  of  Surfaces  produced  by 

Sub-aerial  and  Marine  Denudation."   Geol.  Mag.,  Ill  (1866),  439-451. 
McGee,  W.  J.    "Three  Formations  of  the  Middle  Atlantic  Slope."    Am. 

Jour.  Sci.,  XXXV  (1888). 

Mclntosh.     Scenery  of  England  and  Wales.    1869. 
Penck,  A.     (a)  "  Das  Endziel  der  Erosion  und  Denudation."    Verh.  VIII. 

Deut.  Geographentages  (1889),  91-100. 
(£)  Landerkunde  des  Erdtheils  Europa,  I  (1887),  316. 
(c}  Morphologic  der  Erdoberflache,  II  (1894),  145,  181,489. 
Philippson,  A.    Studieixiiber  Wasserscheiden.     1886. 
Powell,  J.  W.     (a)  Exploration  of  the  Colorado  River.     1875. 
(£)  Geology  of  the  Uinta  Mountains.     1876. 

(c)  Nat.  Geog.  Mon.,  Nos.  i  and  2  (1895). 
Pumpelly,  R.     Bull.  Geol.  Soc.  Am.,  II  (1891),  211. 

Ramsay,  A.  C.     (a)   "  Denudation  of  South   Wales."    Mem.  Geol.  Surv. 
Great  Britain,  I  (1846). 

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(£)  Fiihrer  fur  Forschungsreisende.     Berlin,  1886. 


MARINE  AND  SUB-AERIAL  DENUDATION  349 

Salisbury,  R.  D.     Geol.  Surv.  New  Jersey,  1894  (1895). 

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the  Ground.-"  Geol.  Mag.,  IV  (1867),  3-io. 


XVII 

THE  PENEPLAIN1 

At  the  beginning  of  this  essay  I  wish  to  emphasize  the  fact 
that  the  " peneplain  idea"  was  not  original  with  me.  The  name 
is  of  my  invention,  and,  as  has  sometimes  happened,  the  introduc- 
tion of  a  definite  name  for  a  thing  previously  talked  about  only  in 
general  terms  has  promoted  its  consideration :  witness  the  name 
"  antecedent "  for  rivers  that  hold  their  courses  against  moun- 
tains uplifted  beneath  them.  The  idea  of  antecedent  rivers  had 
occurred  to  several  observers  who  gave  it  no  name,  and  unnamed 
it  gained  no  general  currency ;  but  it  became  popular  when 
Powell  named  it.  Moreover,  the  ideas  of  antecedence  and  pene- 
planation  were  ripe  in  many  minds  about  the  time  the  names 
were  suggested,  and  it  is  chiefly  for  that  reason,  as  it  seems  to 
me,  that  antecedent  rivers  have  been  so  frequently  mentioned  in 
the  last  thirty  years,  and  peneplains  in  the  last  ten. 

It  was  in  Powell's  "  Exploration  of  the  Colorado  River " 
(1875)  that  the  peneplain  idea,  along  with  a  number  of  other 
important  facts  and  principles,  first  came  to  my  notice.  The 
idea  is  not  stated  categorically,  but  when  describing  the  even 
surface  of  deformed  rocks  beneath  the  horizontal  Carboniferous 
strata  in  the  Colorado  canon,  Powell  said  that  "  aerial  forces 
carried  away  10,000  feet  of  rocks  by  a  process  slow  yet  unre- 
lenting, until  the  sea  again  rolled  over  the  land,"  and  the  evehly 
denuded  surface  is  referred  to  as  "  the  record  of  a  long  time 
when  the  region  was  dry  land"  (212).  In  his  "  Geology  of  the 
Uinta  Mountains"  (1876)  the  same  author  writes:  "  Mountains 
cannot  long  remain  as  mountains ;  they  are  ephemeral  topo- 
graphical forms.  Geologically  speaking,  all  existing  mountains 
are  recent;  the  ancient  mountains  are  gone  "(196). 

1  Revised  form  of  a  paper  originally  prepared  as  a  reply  to  an  article  on  "  The 
Peneplain,"  published  by  Professor  R.  S.  Tarr  in  the  American  Geologist,  June,  1898. 

350 


;THE  PENEPLAIN:  351 

Again : 

In  a  very  low  degree  of  declivity  approaching  horizontality,  the  power 
of  transporting  material  is  also  very  small.  The  degradation  of  the  last  few 
inches  of  a  broad  area  of  land  above  the  level  of  the  sea  would  require  a 
longer  time  than  all  the  thousands  of  feet  which  might  have  been  above  it, 
so  far  as  this  degradation  depends  on  mechanical  process,  —  that  is,  driving 
or  flotation ;  but  here  the  disintegration  by  solution  and  the  transportation 
of  material  by  the  agency  of  fluidity  come  in  to  assist  the  slow  processes  of 
mechanical  degradation,  and  finally  perform  the  chief  part  of  the  task  (b,  196). 

Button  referred  to  Powell's  having  given  precision  to  the  idea 
of  base-level,  an  idea  probably  known  previously  in  a  general 
way  to  many  geologists.  "All  regions,"  Button  says,  "are  tend- 
ing to  base-levels  of  erosion,  and  if  the  time  be  long  enough,  each 
region  will,  in  its  turn,  approach  nearer  and  nearer,  and  at  last 
sensibly  reach  it  "  (76). 

I  had  expected  to  find  some  similar  sentences  in  Gilbert's 
"Geology  of  the  Henry  Mountains,"  but  discover  instead  the 
following  statement : 

It  is  evident  that  if  steep  slopes  are  worn  more  rapidly  than  gentle,  the 
tendency  is  to  abolish  all  differences  of  slope  and  produce  uniformity.  The 
law  of  uniformity  of  slope  thus  opposes  diversity  of  topography,  and  if  not 
complemented  by  other  laws,  would  reduce  all  drainage  basins  to  plains. 
But  in  reality  it  is  never  free  to  work  out  its  full  results,  for  it  demands  a 
uniformity  of  conditions  which  nowhere  exists  (115). 

In  Great  Britain,  where  the  literature  very  generally  indicates 
a  belief  in  plains  of  marine  abrasion,  a  number  of  geologists  have, 
without  public  announcement  in  any  formal  manner,  gradually 
enlarged  the  share  of  work  attributed  to  sub-aerial  forces,  until, 
as  some  of  them  have  lately  assured  me,  the  peneplain  idea  has 
come  to  be  for  a  number  of  years  as  familiar  to  them  as  to  most 
American  geologists  ;  and  some  of  them  certainly  entertained  it 
before  the  term  "peneplain"  was  suggested.  Several  examples 
of  the  recognition  of  the  peneplain  idea  by  continental  geologists 
might  be  given  if  time  and  space  permitted. 

The  peneplain  theory  has  been  criticised  on  the  ground  that 
certain  regions  instanced  as  dissected  peneplains  have  never 
really  been  lowlands  of  faint  relief ;  that  the  process  of  pene- 
planation  is  in  itself  an  extremely  unlikely  one  ;  and  that  the  so- 
called  peneplains,  all  of  which  are  now  more  or  less  dissected, 


352  PHYSIOGRAPHIC  ESSAYS 

are  capable  of  other  explanation  ;  in  brief,  that  peneplains  are 
(A)  unreal,  (B)  improbable,  and  (C)  unnecessary.  Several  sub- 
divisions of  each  of  these  headings  will  be  made  in  replying 
to  them. 

A  i .  Certain  Regions  show  no  Trace  of  Peneplanation.  It  has 
been  stated  that  "one  standing  upon  the  crest  of  one  of  the 
mountains  of  central  Maine  would  hardly  find  the  evenness  [of 
the  sky  line]  sufficient  to  give  the  appearance  of  levelness  even 
to  the  eye."  But  no  one,  so  far  as  I  know,  has  thought  that  the 
mountain  tops  of  Maine  mark  the  remnants  of  a  peneplain.  The 
mountains  there  are  probably  of  the  nature  of  monadnocks  ;  it 
is  only  the  general  upland  surface  above  which  the  mountains 
rise  that  can  be  regarded  as  a  peneplain,  uplifted  and  dissected, 
if  the  features  that  I  have  seen  about  Portland  and  at  some  other 
points  along  the  coast  may  be  extended  inland.  The  White 
mountains  have  been,  in  my  mind,  tentatively  classed  as  a  group 
of  monadnocks ;  they  do  not,  as  far  as  I  have  seen  them  in  brief 
excursions,  stand  upon  any  distinct  basement  comparable  to  that 
of  the  uplands  of  New  England  farther  south  ;  but  Mr.  Philip 
Emerson,  master  of  the  Cobbett  school,  Lynn,  tells  me  that  he 
has  in  summer  excursions  traced  what  he  thinks  may  be  regarded 
as  the  extension  of  the  more  southern  uplands  around  the  White 
mountains  on  the  east,  north,  and  west.  Northern  New  England 
is  not  to-day  well  enough  mapped  or  studied  to  give  either 
decided  support  or  disproof  to  the  theory  of  peneplains.  Its 
ruggedness  is  generally  so  great  that  it  is  quite  possible  that  the 
peneplain  explanation  does  not  apply  to  the  greater  part  of  the 
area.  Little  wonder  that  an  observer  whose  attention  is  given  to 
this  mountainous  district,  under  the  impression  that  its  mountain 
tops  represent  the  remnants  of  a  peneplain,  should  come  to  dis- 
credit such  an  explanation. 

A  2.  The  Uplands  of  Southern  New  England  and  of  'Northern 
New  Jersey  are  not  of  Uniform  Altitude.  It  has  been  urged  that 
a  careful  examination  of  the  topographical  maps  of  these  regions 
disproves  the  accordance  claimed  for  their  upland  altitudes.  In 
answer,  I  should  say  that  the  lack  of  uniformity  among  the 
uplands — a  fact  perfectly  familiar  to  those  who  accept  the  pene- 
plain idea  —  is  partly  the  result  of  tilting,  as  will  be  further 


THE  PENEPLAIN  353 

considered  below  (see  A  4) ;  and  that  for  the  rest  the  unevenness 
of  the  uplands  of  to-day  is  a  natural  result  of  imperfect  pene- 
planation  followed  by  sub-mature  dissection.  The  examination 
of  the  peneplain  remnants  by  means  of  topographical  maps  is 
not  a  new  method  of  investigation,  as  it  was  employed  for  New 
Jersey  in  1888-1889,  and  for  southern  New  England  a  few 
years  later;  but,  like  observation  outdoors,  it  seems  to  lead 
different  investigators  to  different  results..  Considerable  as  the 
inequalities  of  altitude  are,  frequent  study  of  the  maps  and 
repeated  views  of  the  uplands  from  various  hill-tops  impress  me 
much  more  with  .the  relative  accordance  of  their  altitudes  than 
with  their  diversity.  I  cannot  admit  that  the  appearance  of  ac- 
cordance from  hill-top  to  hill-top  is  an  optical  deception.  There 
is  an  important  matter  of  fact  behind  the  appearance. 

The  comparative  evenness  of  the  uplands  in  Connecticut  was 
recognized  and  well  described  by  Percival  over  half  a  century 
ago.  The  state  being  divided  into  eastern  and  western  areas  of 
primary  r®cks  by  the  trough  of  Triassic  strata,  he  said : 

The  eastern  and  western  primary  may  both  be  regarded  as  extensive 
plateaus,  usually  terminating  abruptly  toward  the  larger  secondary  basin, 
but  sinking  more  gradually  toward  the  south,  on  the  sound.  These  plateaus 
present,  when  viewed  from  an  elevated  point  on  their  surface,  the  appear- 
ance of  a  general  level,  with  a  rolling  or  undulating  outline,  over  which  the 
view  often  extends  to  a  very  great  distance,  interrupted  only  by  isolated 
summits  or  ridges,  usually  of  small  extent.  These  plateaus  are  also  inter- 
sected by  valleys  and  basins,  which  serve  to  mark  the  arrangement  of  their 
surface  even  more  definitely  than  the  elevations.  This  arrangement  will  be 
found  to  correspond  very  exactly  with  that  of  the  geological  formation, 
indicating  that  it  was  caused  essentially  by  the  original  form  of  the  surface 
of  these  formations,  and  not  by  any  subsequent  denudation  (477)- 

The  western  primary  .  .  .  forms,  within  the  limits  of  this  state,  a  wide 
plateau  ...  of  so  uniform  an  elevation  that  from  many  points  the  view 
extends  across  its  entire  width,  and  to  a  great  distance  north  and  south  (478). 

The  eastern  primary,  viewed  from  its  more  elevated  points,  presents  the 
same  general  appearance  as  the  western :  that  of  an  extensive  undulating 
surface  of  nearly  uniform  elevation,  diversified  by  detached  summits  (482). 

The  peculiar  conclusion  of  the  first  of  the  above  quotations  is 
interesting  in  contrast  to  modern  views. 

In  eastern  Massachusetts  dissection  has  gone  so  far  that  it 
would  be  difficult  to  discover  an  uplifted  peneplain  on  local 


354  PHYSIOGRAPHIC  ESSAYS 

evidence  alone  ;  but  in  the  central  and  western  parts  of  the  state 
the  uplands  are  generally  well  defined  and  very  accordant.  Look- 
ing eastward  from  the  Berkshire  hills  across  the  Connecticut 
valley  lowlands  in  northern  Massachusetts,  the  sky  line  of  the 
central  plateau  is  astonishingly  uniform,  though  its  altitude  is 
over  a  thousand  feet. 

A3.  The  Remains  of  Certain  Peneplains  are  Fragmentary. 
It  has  been  urged  that  ten  per  cent  of  the  original  area  of  the 
supposed  peneplain,  now  preserved  in  the  uplands  of  Connecticut, 
is  too  small  a  fraction  to  serve  as  a  basis  of  reconstruction. 
This  does  not  strike  me  as  a  serious  or  a  novel  difficulty.  Geol- 
ogists are  often  compelled  to  work  on  fragmentary  evidence  ; 
they  are  satisfied  if  the  fragments  can  be  logically  built  up  into 
the  complete  structure.  In  most  parts  of  the  world  rock  out- 
crops occupy  less  than  ten  per  cent — often  less  than  one  per 
cent  —  of  the  land  surface,  yet  no  field  geologist  hesitates  to 
"color  in  "  a  formation  over  an  area  where  scattered  outcrops 
give  reasonable  proof  of  its  occurrence.  The  surface  area  thus 
colored  in  is  often  but  a  small  part  of  the  entire  body  of  the 
original  formation,  which  may  be  largely  covered  by  later 
deposits  or  destroyed  by  erosion ;  but  the  covered  and  eroded 
portions  are  reasonably  inferred,  and  a  formation  thus  established 
is  a  stock  subject  in  historical  geology.  A  high  percentage  of 
direct  observation  is  less  essential  than  a  logical  method  of  recon- 
structing the  unseen  whole  from  the  observed  parts.  Here  the 
dissected  peneplain  seems  to  me  to  stand  on  a  par  with  many 
other  things.  Its  fragmental  condition  is  most  natural ;  its  dis- 
covered parts  are  connected  and  the  lost  peneplain  is  restored  by 
a  line  of  argument  that  is  perfectly  reasonable  in  itself,  and  that 
is  objected  to  only  because  it  runs  counter  to  certain  views  that 
are  held  to  be  established  principles  in  the  science  of  geology. 
These  views  will  be  considered  below  (B  i,  2). 

A  4.  Certain  So-called  Peneplains  are  now  Inclined.  It  has 
been  stated  that  uplift  or  tilting  "is  an  assumption  rendered 
necessary  to  explain  the  difference  in  elevation  of  the  supposed 
peneplain,  but  there  is  no  evidence  to  prove  it  unless  the  pene- 
plain be  previously  accepted."  With  this  I  fully  agree.  I  have 
repeatedly  insisted  that  it  was  only  by  recognizing  the  existence 


THE  PENEPLAIN  355 

of  a  peneplain  that  uplift  or  deformation  could  be  determined  in 
certain  cases ;  and  that  only  in  this  way  could  certain  stages 
of  geological  history  be  discovered,  in  the  absence  of  what  might 
be  called  orthodox  geological  evidence  in  the  form  of  marine 
deposits.  For  example,  it  is  by  the  remnants  of  an  uplifted, 
inclined,  and  warped  peneplain  in  the  even  crest  lines  of  the 
Pennsylvania  Appalachians  that  the  post-Cretaceous  uplift  of 
the  mountain  belt  has  been  determined ;  it  was  formerly  sup- 
posed that  the  existing  ridges  were  the  unconsumed  remnants 
of  the  ancient  Appalachians,  and,  by  implication,  that  no  uplift 
of  the  region  had  occurred  since  the  mountains  were  crushed, 
folded,  and  upheaved.  So  in  southern  New  England  :  there  was 
no  means  of  determining  the  date  of  uplift,  as  a  result  of  which 
the  existing  valleys  were  eroded,  until  the  peneplain  of  the 
uplands  was  recognized  and  dated.  Twenty  or  thirty  years  ago 
it  was  not  uncommon  to  meet  the  suggestion  that  the  valleys 
might  be  of  glacial  origin,  so  little  understanding  had  then  been 
reached  of  the  geographical  development  of  the  region.  Those 
who  believe  in  the  verity  of  peneplains  will  infer  uplift  where  they 
see  a  high-standing  and  dissected  peneplain  as  confidently  as  the 
geologists  of  the  end  of  the  eighteenth  century  inferred  uplift  when 
they  found  marine  fossils  in  stratified  rocks  far  above  sea-level. 

But  it  does  not  seem  warranted  to  conclude  that  the  peneplain 
theory  is  invalidated  because  certain  peneplains  are  now  uplifted 
on  a  slant.  It  is  no  objection  to  the  peneplain  idea  to  say  that 
the  crest  of  Kittatinny  mountain  is  higher  than  the  upland  sur- 
face of  the  New  Jersey  highlands,  or  that  the  crest  of  the 
Palisades  is  lower.  It  would  be  as  extraordinary  to  find  no 
slanting  peneplains  as  to  find  no  inclined  strata.  Warped  and 
faulted  peneplains  are  no  more  unlikely  products  of  crustal  defor- 
mation than  warped  and  faulted  sedimentary  formations  ;  witness 
the  dislocations  of  the  plateaus  trenched  by  the  Colorado  canon, 
the  plateau  surface  having  been  worn  down  to  "a  very  flat 
expanse"  before  the  uplift  and  displacements  that  have  deter- 
mined the  altitudes  and  forms  of  to-day. 

A  5 .  Objections  based  on  the  Fragmentary  Condition  of  Cer- 
tain Peneplains  fttrther  Considered.  If  the  best-preserved  pene- 
plains were  not  less  fragmentary  than  those  of  New  England  and 


356  PHYSIOGRAPHIC  ESSAYS 

New  Jersey,  the  theory  of  peneplains  might  perhaps  be  over- 
thrown; but  when  these  imperfect  peneplains  are  considered  in 
connection  with  many  more  nearly  perfect  peneplains  elsewhere, 
the  series  becomes  so  well  graded,  from  better  to  worse,  that  the 
theory  seems  to  me  unassailable.  A  few  examples  of  the  better- 
preserved  peneplains  may  therefore  be  now  considered. 

The  Piedmont  belt  of  Virginia  has  been  described  by  a  num- 
ber of  observers  in  recent  years.  McGee  writes  :  "  The  plain  is 
not  monotonously  smooth  ;  here  it  undulates  in  graceful  swells, 
there  it  dips  into  rocky  river  gorges,  winding  across  its  width 
....  Such  is  the  Piedmont  plain  within  view  of  Monticello, 
and  such  is  the  province  throughout  its  extent  from  New  York 
to  Alabama  "  (261).  The  Piedmont  rivers  "  rush  through  narrow, 
rockbound  gorges.  .  .  .  All  the  Piedmont  rivers,  large  and  small, 
are  incessantly  corrading  their  beds  "  (262).  The  plain  "must  be 
regarded  as  the  basal  portion  of  a  vast  mass  of  inclined  rocks  of 
which  an  unmeasured  upper  portion  has  been  planed  away"  (263). 
In  describing  the  same  region,  Darton  writes  :  "  The  Piedmont 
plateau  is  a  peneplain  of  Tertiary  age  .  .  .  the  plain  has  been 
deeply  trenched  by  drainage  ways,  but  wide  areas  are  preserved 

on  the  divides  " 
(570).  He  be- 
lieves that  this 
peneplain  (AB, 

Fig.  7)  continues  across  the  inner  strata  (BC]  of  the  coastal  plain, 
and  that  it  should  therefore  be  distinguished  from  an  earlier  pene- 
plain carved  on  the  same  ancient  rocks,  part  of  which  is  BE, 
preserved  beneath  the  strata  of  the  coastal  plain,  and  part  of 
which  (DJ3]  is  generally  hereabout  destroyed  by  erosion.  It  is 
upon  the  older  peneplain  that  the  Potomac  formation,  with  its 
fossil  terrestrial  flora,  directly  rests.  Keith  gives  an  elaborate 
account  of  a  part  of  the  Piedmont  plain  in  his  "  Geology  of  the 
Catoctin  Belt"  and  discusses  its  relations  to  various  members  of 
the  coastal-plain  series. 

Any  one  who  will  follow  up  the  foregoing  references,  or  who 
will,  better  still,  look  over  the  region  on  the  ground,  will  find  a 
decidedly  larger  portion  of  the  peneplain  surface  preserved  than 
is  the  case  in  New  England  or  New  Jersey ;  and  this  is  most 


THE  PENEPLAIN  357 

natural,  for  the  Virginia  Piedmont  plain  is  of  distinctly  later 
origin  than  the  peneplain  of  the  uplands  farther  north  :  the 
latter  corresponds  to  the  earlier  peneplain  (DBE}  in  Virginia. 
But  it  is  not  only  the  comparative  continuity  of  the  Piedmont 
plain  that  makes  it  a  valuable  example :  the  deep  soils  of  the 
upland  plain  and  the  rocky  walls  of  the  narrow,  steep-sided 
valleys  are  as  important  witnesses  to  the  once  lower  position  of 
the  plain  and  to  the  uplift  by  which  its  present  altitude  has 
been  gained  as  are  the  forms  of  the  upland  and  the  valleys.  To 
explain  this  point  more  fully,  a  brief  digression  may  be  allowed. 
The  peneplain  is  only  one  element  in  the  theory  of  the  geo- 
graphical cycle.  The  systematic  sequence  in  the  development  of 
land  forms  through  the  cycle  is  a  much  larger  and  more  impor- 
tant principle  than  the  penultimate  development  of  a  peneplain, 
considered  alone,  for  the  former  includes  the  latter.  One  of  the 
elements  of  the  cycle  is  the  development  of  the  graded  condition 
of  streams  of  water  during  maturity,  whereby  an  essential  agree- 
ment is  brought  about  between  the  ability  of  a  stream  to  do 
work  and  the  work  that  it  has  to  do.  Another  element,  less  gen- 
erally recognized,  is  the  development  of  the  graded  condition  in 
the  streams  and  sheets  of  rock  waste  or  soil  on  sloping  surfaces, 
where  no  running  streams  of  water  occur.  By  following  out  the 
ideal  scheme  thus  suggested,  it  must  result  that  just  as  the 
graded  condition  of  water  -streams  is  normally  propagated  from 
the  mouth  towards  the  head,  and  in  time  reaches  the  source  of 
all  the  branches,  so  the  graded  condition  of  soil-covered  slopes  is 
in  time  extended  all  over  a  land  surface,  from  the  valley  floors 
to  the  divides.  The  supply  of  waste  by  the  disintegration  of  the 
sub-soil  rock  is  then  everywhere  essentially  equal  to  its  removal 
by  all  available  agents  of  transportation.  In  a  late  stage  of  a 
cycle,  when  the  surface  slopes  are  small,  agents  of  transportation 
are  weak ;  hence  the  supply  of  waste  must  then  be  slow  and  the 
waste  to  be  removed  must  be  of  fine  texture.  In  order  that  the 
supply  shall  be  slow,  the  waste  comes  to  have  a  great  depth,  and 
the  upper  parts  greatly  protect  the  rock  beneath  from  the  attack 
of  the  weather.  At  the  same  time,  transportation  is  facilitated 
by  the  refinement  of  the  surface  soil  during  its  long  exposure  to 
the  weather.  Hence,  under  ordinary  climatic  conditions,  normal 


358  PHYSIOGRAPHIC  ESSAYS 

peneplains  must  have  deep  local  soils  of  fine  texture  at  the  sur- 
face, and  grading  into  firm  rock  at  a  depth  of  thirty,  fifty,  or 
more  feet.  Moreover,  it  is  only  on  a  lowland  surface  of  small 
slope  that  such  a  depth  and  arrangement  of  local  soil  can  be 
normally  produced. 

In  contrast  to  the  deep  soil  of  a  peneplain,  the  steep  sides  of 
young  valleys,  whose  graded  waste  sheets  are  not  yet  developed, 
must  frequently  reveal  bare,  rocky  ledges.  Only  as  the  valleys 
widen  and  their  side  slopes  become  somewhat  more  gentle  will 
the  ledges  disappear ;  and  even  then  the  rock  will  be  covered 
only  by  a  relatively  thin  and  coarse  sheet  of  rapidly  creeping 
waste.  It  therefore  follows  that  the  uplands  of  the  Piedmont 
belt,  with  their  deep  soil,  are  of  an  essentially  different  cycle  of 
development  from  the  narrow  valleys,  with  their  bare  ledges. 
The  two  elements  of  form  remain  mutually  inconsistent  until 
reconciled  by  the  postulate  of  an  uplift  of  the  region  between 
their  developments.  But  if  this  postulate  is  accepted,  the  plain 
is  shown  to  have  been  a  lowland  of  faint  relief  before  the  existing 
narrow  valleys  were  cut  in  it.  It  is  this  double  line  of  argument, 
based  on  deep  soil  and  bare  ledge,  as  well  as  undulating  plain 
and  narrow  valley,  that  has  convinced  various  observers  of  the 
verity  of  the  peneplain  in  the  Piedmont  belt. 

The  Great  Plains  of  eastern  Montana  include  an  area  of 
nearly  horizontal  Cretaceous  strata  -on  either  side  of  the  Mis- 
souri river,  regarding  which  the  evidence  of  peneplanation  seems 
to  me  beyond  dispute.  Here  and  there  volcanic  buttes,  dikes, 
and  mesas  surmount  the  plain  by  several  hundred  feet ;  on  the 
south  the  Highwood  mountains,  a  network  of  dikes  among  nearly 
horizontal  shales  and  sandstones,  rise  in  still  stronger  relief. 
Hence  there  can  be  no  question  that  strata,  measuring  hundreds, 
if  not  thousands,  of  feet  in  thickness,  have  been  broadly  removed 
from  the  region  by  denudation.  Yet  the  surface  between  the 
various  eminences  that  rise  above  it  is  a  true  geographical  plain. 
It  is  not  absolutely  level,  but  broadly  undulating,  with  a  sky  line 
almost  as  even  as  that  of  the  ocean  itself.  In  this  plain  the 
Missouri  river  and  its  chief  branches  have  cut  narrow,  steep- 
sided  valleys  several  hundred  feet  below  the  general  upland 
level.  These  valleys  are  so  young  that  the  Missouri  itself  has 


THE  PENEPLAIN  359 

not  yet  developed  an  even  slope :  witness  its  several  leaps  at 
Great  Falls.  Innumerable  wet-weather  side  streams  are  cutting 
sharp  ravines  in  the  larger  valley  sides.  It  does  not  seem  possi- 
ble to  avoid  concluding  that  the  upland  plain  is  to-day  in  process 
of  destruction  by  an  agency  that  could  not  have  been  in  operation 
while  the  finishing  touches  were  given  to  its  production.  It  was 
upon  this  peneplain  in  1883  that  the  necessity  of  believing  in 
penultimate  denudation  was  first  strongly  impressed  upon  me. 
Dr.  Waldemar  Lindgren,  now  of  the  United  States  Geological 
Survey,  who  was  with  me  in  the  field,  may  recall  how  the  con- 
viction grew  upon  our  minds  ;  if  I  am  not  mistaken,  he  accepted 
it  before  I  did.  A  brief  account  of  the  region  is  published  in 
Volume  XV  of  the  Tenth  United  States  Census  Reports. 

The  extended  plains  of  central  Russia,  as  lately  described  by 
Philippson,  have  a  gently  undulating  surface  at  a  height  of  two 
hundred  or  three  hundred  meters,  broadly  continuous,  but  here 
and  there  dissected  by  relatively  narrow,  steep-sided  young 
valleys.  The  upland  surface  is  not  a  structural  plain,  for  it 
bevels  across  formations  of  very  different  ages ;  it  is  therefore  a 
plain  of  erosion.  In  the  south  there  is  a  partial  covering  of  loess, 
a  thin  veneer  often  absent  and  leaving  the  rock  surface  visible 
over  large  areas.  In  the  north  the  drift  cover  is  heavier  and 
more  continuous,  but  the  plateau  surface  is  still  the  continuation 
of  the  same  plain  of  erosion  as  in  the  south.  There  is  no  record 
of  marine  action  on  the  great  plain,  hence  its  erosion  is  ascribed 
to  the  lateral  swinging  of  the  lower  courses  of  large  rivers  ;  but 
the  origin  of  the  rivers  is  unknown  :  it  can  only  be  said  that 
when  the  erosion  was  going  on,  the  Russian  "  Scholle  "  must 
have  stood  two  hundred  meters  lower  than  to-day.  The  narrow 
valleys  have  been  cut  since  the  uplift  of  the  plain  and  are  older 
than  the  glacial  period.  This  is  the  largest  peneplain  of  which 
I  have  found  any  account. 

A  6.  The  Asserted  Discordance  of  Peneplain  Surface  and 
Rock  Structure  is  open  to  Question.  It  has  been  said  to  be 
questionable  whether  there  is,  after  all,  such  a  lack  of  sympathy 
between  topography  and  rock  structure  as  has  been  represented, 
and  in  evidence  of  this  doubt  one  has  urged  that  in  the  high- 
lands of  New  Jersey  there  is  "  a  very  evident  general  sympathy 


360  PHYSIOGRAPHIC  ESSAYS 

between  the  present  topography  and  the  rock  texture."  This 
objection  to  peneplanation  does  not  meet  the  arguments  advanced 
in  its  favor.  Disregarding  the  weaker  structures,  which  are  now 
worn  down  beneath  the  inferred  surface  of  the  peneplain,  it 
seems  to  me  undeniable  that  the  peneplain  surface  was  strongly 
discordant  with  the  hard  structures  that  still  preserve  its  rem- 
nants. It  is  a  matter  of  necessity  that  the  present  topography 
of  an  uplifted  and  dissected  peneplain  should  exhibit  sympathy 
between  form  and  structure,  for  where  should  better  accordance 
of  form  and  structure  be  expected  than  in  such  a  region  of 
adjusted  drainage ;  but  this  is  a  matter  quite  apart' from  the 
present  discussion. 

Various  gneisses,  sandstones,  and  trap  sheets,  standing  in  a 
more  or  less  inclined  position,  are  truncated  with  good  appearance 
of  system  by  the  gently  slanting  surface  of  the  peneplain  of 
northern  New  Jersey.  The  following  description  of  the  region 
is  taken  from  one  of  Cook's  reports. 

The  Highland  mountain  range  consists  of  many  ridges  which  are  in  part 
separated  by  deep  valleys  and  in  part  coalesce,  forming  plateaus  or  table- 
lands of  small  extent.  ...  A  characteristic  feature  is  the  absence  of 
what  might  be  called  Alpine  structure  [form?]  or  scenery.  There  are  no 
prominent  peaks  or  cones.  The  ridges  are  even-topped  for  long  distances,  and 
the  average  elevation  is  uniform  over  wide  areas.  Looking  at  the  crests 
alone  and  imagining  the  valleys  and  depressions  filled,  the  surface  would 
approximate  to  a  plane  gently  inclined  toward  the  southeast  and  toward 
the  southwest  (27). 

It  is  this  indifference  of  the  peneplain  to  the  various  struc- 
tures that  it  systematically  truncates  that  has  always  been  the 
chief  argument  of  those  who  thought  they  saw  traces  of  a  former 
lowland  where  there  is  to-day  a  dissected  highland,  whether  they 
believed  in  marine  abrasion  or  in  sub-aerial  denudation. 

Special  mention  may  be  made  here  of  certain  features  that 
will  be  referred  to  more  briefly  in  a  later  section.  Descending 
the  Hudson  from  Haverstraw  to  Jersey  City,  one  may  see  a 
gradual  decrease  of  altitude  in  the  Palisades,  a  ridge  formed  on 
a  monoclinal  sheet  of  dense,  intrusive  trap,  from  a  height  of 
about  six  hundred  feet  in  the  north  to  sea-level  in  the  south. 
There  is  no  corresponding  variation  in  the  thickness  of  the  trap 


THE  PENEPLAIN  361 

sheet.  The  uplands  of  schists  and  gneisses  on  the  east  of  the 
Hudson  have  a  similar  descent  from  the  Highlands  to  Long 
Island  sound.  In  Connecticut  the  view  from  East  Rock,  New 
Haven,  discloses  the  extraordinarily  even  crest  line  of  Totoket 
mountain,-  the  edge  of  a  strongly  warped  sheet  of  extrusive  trap. 
The  crest  line  slowly  descends  southward  and  is  continued  by 
the  somewhat  lower  crest  line  of  Pond  mountain,  of  similar 
structure.  Furthermore,  the  descent  of  these  crest  lines  agrees 
very  well  with  the  descent  of  the  crystalline  uplands  next  on  the 
east.  The  systematic  relation  of  these  and  many  other  crest 
lines  and  uplands  suggests  a  peneplain,  and  the  peneplain  thus 
inferred  is  strikingly  indifferent  to  the  structures  that  it  truncates. 
It  might  be  urged  that  the  observed  discordance  of  form  and 
structure  is  of  some  other  origin  than  peneplanation,  but  the 
discordance  does  not  seem  open  to  question. 

A  7.  The  Rocks  of  Monadnocks  are  not  proved  to  be  more 
Resistant  than  those  of  the  Adjoining  Peneplain.  It  has  been 
urged  that  there  is  no  proof  of  the  durability  of  the  rocks  of 
monadnocks  other  "than  that  which  comes  from  the  necessity 
of  such  an  explanation,  made  necessary  by  first  accepting  the 
existence  of  the  peneplain."  As  far  as  my  own  work  is  con- 
cerned, there  is  some  ground  for  this  objection.  I  have  as  a 
rule  given  no  particular  attention  to  the  composition  of  the 
monadnock  rocks ;  indeed,  it  has  generally  seemed  to  me  rea- 
sonable to  infer  their  greater  resistance  on  account  of  their  form. 
But  so  far  as  attention  has  been  given  directly  to  this  phase  of 
the  problem,  the  inference  based  on  the  peneplain  theory  is 
borne  out  by  petrographic  study.  The  buttes  and  mesas  that 
surmount  the  plains  of  the  upper  Missouri  are  maintained  by 
dense  igneous  rocks.  The  monadnocks  of  the  Virginia  Piedmont 
belt  "  are  ribbed  with  siliceous  schists  or  quartzites  or  other  rocks 
that  resist  well  the  work  of  the  weather  .  .  .,  while  the  rocks 
underlying  the  fertile  fields  of  the  plain  are  softer  schists,  easily 
weathered  and  worn  away"  (McGee,  262,  263).  Near  Atlanta, 
Georgia,  the  Piedmont  area  is  a  well-finished  peneplain,  rather 
strongly  dissected,  with  deep  soils  overlying  the  uplands  of  gneiss 
and  schist.  Stone  mountain,  a  superb  monadnock  of  abrupt  form, 
consists  of  fine  homogeneous  granite,  quite  unlike  the  rocks  of  the 


362  PHYSIOGRAPHIC  ESSAYS 

peneplain  (Purington,  105-108).  Van  Hise,  in  describing  the 
uplands  of  the  ancient  disordered  and  indurated  rocks  in  north- 
central  Wisconsin,  says  that  they  constitute  "as  nearly  perfect  a 
base-level  plain  as  it  has  been  my  good  fortune  to  see.  .  .  .  Above 
the  valley  of  the  Wisconsin  river  an  almost  perfect  plain  is  seen  . . ., 
large  areas  of  which  are  but  little  dissected  by  any  of  the  tribu- 
tary streams  of  the  Wisconsin."  The  upland  plain  is  surmounted 
by  Big  Rib  hill,-  a  monadnock  of  exceedingly  resistant  quartzite. 
The  upland  of  the  Slate  mountains  in  western  Germany  is  a 
wonderfully  fine  peneplain  of  broad  and  gentle  undulations,  now 
undergoing  active  dissection  by  the  branches  of  the  Rhine, 
Moselle,  and  other  strong  rivers  which  have  eroded  their  steep- 
sided  valleys  deep  beneath  its  even  surface.  The  upland  is 
surmounted  by  several  ridges  or  elongated  monadnocks ;  and 
some  of  these  at  least  are  composed  of  a  very  resistant  quartzite. 
In  New  England  the  "Monadnock"  is,  if  my  memory  serves  me, 
largely  composed  of  an  andalusite  schist,  which  certainly  has 
every  appearance  of  being  a  resistant  rock.  Yet  I  must  freely 
admit  that,  as  far  as  I  know,  no  artificial  test  has  been  made  of 
its  resistance  as  compared  with  that  of  many  apparently  resist- 
ant rocks  around  its  base.  It  may  be  added  that  an  appropriate 
test  would  be  difficult  to  devise,  inasmuch  as  exposure  for  ages 
to  the  weather  would  certainly  be  the  best  means  of  discover- 
ing the  way  in  which  long  ages  of  weathering  will  affect  a 
rock.  In  view  of  this  difficulty  I  hope  that  those  who  regard 
the  peneplain  explanation  as  compulsory  will  not  be  left  alone  to 
devise  appropriate  tests  to  determine  the  resistance  of  monad- 
nock  rocks,  but  that  others  who  are  interested  in  the  develop- 
ment of  land  forms,  but  who  feel  no  such  compulsion  from  the 
peneplain  theory,  will  nevertheless  turn  their  ingenuity  in  this 
direction.  It  is  the  truth  of  the  matter  that  we  are  all  striving 
for,  not  the  maintenance  of  this  theory  or  that ;  and  it  seems 
unfriendly,  if  not  unscientific,  to  say  that  the  burden  of  proof 
should  rest  with  the  advocates  of  the  peneplain  theory.  We  are 
not  retained  to  argue  for  or  against  the  theory ;  each  of  us 
follows  the  guidance  of  the  best  evidence  he  can  find.  It  is  of 
course  difficult  to  avoid  the  appearance  .and  even  the  style  of  the 
advocate  or  the  enemy  when  writing  earnestly  in  expression  of 


THE  PENEPLAIN  363 

one's  convictions,  but  for  my  part  I  cannot  say  too  emphatically 
that  the  peneplain  idea  shall  find  no_  " defense"  from  me.  Let 
us  all  set  forth  the  pros  and  cons  to  the  best  of  our  ability,  and 
then  the  peneplain  idea  must  look  out  for  itself,  and  stand  or 
fall  according  to  its  value. 

The  objections  thus  far  discussed  relate  to  actual  examples  of 
supposed  peneplains.  Attention  may  be  next  turned  to  a  group 
of  objections  based  on  general  considerations,  leading  to  the  be- 
lief that  the  production  or  occurrence  of  peneplains  is  improbable 
or  even  impossible. 

B  i .  No  Peneplains  are  now  found  standing  close  to  Base-Level. 
It  has  been  stated  that  since  no  extensive  peneplains  are  now 
known  to  exist  in  any  part  of  the  earth,  in  accepting  the  pene- 
plain theory  we  must  assume  that  during  a  part  of  the  remote 
past  the  conditions  have  been  different  from  those  that  have 
prevailed  in  any  part  of  the  known  earth  during  the  present  and 
immediate  past.  As  far  as  my  own  understanding  of  the  prob- 
lem is  concerned,  it  was  not  at  all  as  an  assumption,  but  as  a 
very  surprising  corollary,  that  I  came  upon  the  difference 
between  the  present  and  certain  parts  of  the  past  with  respect 
to  peneplanation. 

Although  agreeing  in  the  belief  that  the  theory  of  peneplains 
involves  a  certain  difference  between  the  past  and  the  present, 
I  do  not  agree  to  the  implication  that  the  past,  "  whose  history 
has  been  worked  out  by  purely  stratigraphic  methods,"  is  proved 
to  be  so  like  the  present  that  the  theory  of  peneplains  must  be 
wrong  because  it  involves  a  past  that  is  in  some  ways  unlike  the 
present.  My  opinion  is  that  stratigraphic  methods  do  not  always 
disclose  a  past  closely  like  the  present  (see  B  4),  and  that,  even 
at  their  best,  stratigraphic  methods  are  not  so  complete  in  their 
revelations  but  that  all  other  lines  of  evidence  concerning  the 
nature  of  the  past  should  have  a  careful  hearing. 

There  are  certain  parts  of  the  world  in  which  frequent  dis- 
orderly movements  of  the  earth's  crust  appear  to  have  continued 
during  several  geological  periods,  including  the  present ;  for 
example,  the  Alps.  The  teachings  of  Mesozoic  and  Genozoic 
stratigraphy  in  such  a  region  would  lend  no  support  to  the 
theory  of  peneplanation,  as  little  support  would  be  gained  from 


364  PHYSIOGRAPHIC  ESSAYS 

the  teachings  of  denudation  in  the  Alps.  Indeed,  I  have  been 
interested  to  learn  that  certain  careful  students  of  geomorphy  in 
the  neighborhood  of  the  Alps  have  recognized  that  they  were 
prejudiced  against  the  theory  because  their  experience  was 
gained  chiefly  in  an  uneasy  part  of  the  world.  But  there  are 
other  parts  of  the  world  which  have  been  relatively  quiescent 
for  long  geological  periods  ;  for  example,  the  upper  Mississippi 
basin,  where  all  represented  formations,  from  the  Cambrian 
down,  are  essentially  horizontal  and  of  moderate  thickness. 
Stratigraphy,  as  there  taught,  would  not  be  inconsistent  with 
peneplanation ;  neither  would  geomorphy,  and  to  illustrate  this 
I  have  a  little  story  to  tell.  During  an  excursion  with  a  friend 
native  to  that  part  of  the  country,  I  pointed  out  the  very  even 
sky  line  of  a  dissected  upland  as  an  example  of  a  peneplain. 
My  friend  dissented,  thinking  no  such  special  explanation  neces- 
sary ;  ordinary  denudation  would  suffice,  he  thought,  to  produce 
the  observed  forms,  without  specification  of  control  by  different 
base-levels.  A  year  later,  on  meeting  the  same  friend,  our  talk 
happened  to  turn  on  peneplains,  and  he  said,  "  I  should  like  to 
show  you  an  excellent  example  of  that  sort  of  thing,"  proceeding 
to  describe  the  very  region  we  had  seen  together.  "How,"  I 
asked,  "did  you  come  upon  that  explanation?"  "I  cannot  say 
precisely  how,"  he  replied;  "it  is  nothing  new."  This  incident 
seems  to  me  to  illustrate  the  unconscious  encouragement  given 
to  the  idea  of  peneplanation  by  a  quiescent  environment,  in  con- 
trast to  the  discouragement  given  in  such  a  region  as  the  Alps. 

Unrest  and  quiescence  are  not  persistent  characteristics  of 
one  region  or  another.  Pre-Cambrian  time  was  active  enough 
in  the  Wisconsin-Minnesota  region ;  and  there  are  indications  of 
relative  quiet  in  the  Alpine  region  before  its  Mesozoic  and 
Cenozoic  activity  began.  But  this  aspect  of  the  problem  is  too 
large  for  consideration  here.  Suffice  it  to  say  that  there  is  yet 
much  to  be  learned  about  the  past,  and  that  I  fully  agree  with 
McGee  in  believing  that  the  world's  history  is  to  be  read  in 
denudation  as  well  as  in  deposition.  If  the  deciphering  of 
trustworthy  records  of  denudation  leads  to  the  conclusion  that 
the  present  is  in  some  respects  exceptional,  a  peculiar  chapter  in 
the  earth's  history,  then  I  should  have  to  add  that  conclusion 


THE  PENEPLAIN  365 

to  the  other  authenticated  conclusions  which  go  to  making 
up  the  history  of  the  planet.  Admitting  the  present  to  be 
exceptional  in  the  lack  of  peneplains  close  to  their  base-level  of 
production,  and  thus  postulating  general  disturbances  by  uplift 
and  tilting  in  the  recent  past,  I  doubt  if  this  condition  is  more 
exceptional  than  that  which  permitted  the  widespread  deposition 
of  the  chalk  of  Europe  upon  its  even  foundation,  or  than  that 
which  determined  the  formation  of  the  coal  measures  of  Europe 
and  North  America.  There  does  not  seem  to  be  any  severe 
strain  upon  the  reasonably  elastic  form  of  the  doctrine  of  unifor- 
mitarianism  in  meeting  the  requirements  of  the  peneplain  theory. 

B  2.  The  Earth '  s  Crust  will  not  stand  still  long  enough  for  the 
Slow  Process  of  Denudation  to  produce  a  Peneplain.  It  is  justly 
urged  that  according  to  theory  the  later  stages  of  peneplanation 
are  much  longer  than  the  early  stages  of  dissection,  as  Powell 
clearly  pointed  out  some  years  ago ;  and  it  has  been  inferred 
that  the  earth's  crust  will  not  stand  still  long  enough  for  even 
penultimate  denudation  to  be  accomplished.  But  the  stability  or 
instability  of  the  earth's  crust  can  be  learned  only  by  comparing 
the  consequences  reasonably  deduced  from  one  condition  or  the 
other  with  observed  facts.  It  seems  to  me  a  prejudgment  of  the 
case  to  enter  it  with  the  conclusion  that  the  lands  do  not  stand 
still  long  enough  for  peneplanation.  Certainly  they  do  not  stand 
still  long  enough  in  certain  regions  ;  witness  the  manifest  effects 
of  uneasiness  in  the  varied  and  unconformable  stratified  deposits, 
or  in  the  repeated  renewals  of  dissection  in  the  Alps.  But  the 
opposite  conclusion  is  enforced  by  both  lines  of  evidence  in  the 
Piedmont  region  of  Virginia. 

Another  example  may  be  taken  from  the  West.  The  upland 
of  the  plateaus  trenched  by  the  Colorado  canon  is  by  no  means 
a  level  surface  ;  but  if  the  fault  cliffs  and  the  monoclinal  slopes 
by  which  it  is  dislocated,  the  canons  by  which  it  is  dissected, 
and  the  volcanic  cones  by  which  it  is  embossed  were  subtracted, 
the  remaining  relief  could  not,  if  one  may  judge  by  Button's 
vivid  descriptions,  be  so  great  but  that  the  surface  might  be 
called  a  peneplain,  especially  if  due  regard  is  had  to  the  vast 
volume  of  material  removed  in  its  preparation,  as  attested  by  the 
huge  cliffs  of  recession  on  the  north.  It  is  true  that  a  certain 


366  PHYSIOGRAPHIC  ESSAYS 

part  of  the  upland  seems  to  be  a  structural  plain  ;  that  is,  its 
surface  agrees  rather  closely  with  that  of  the  more  resistant 
Carboniferous  layers ;  but  when  looked  at  broadly,  the  upland  is 
seen  to  bevel  gently  across  the  edges  of  the  layers,  which  dip 
northward  at  a  faint  angle.  In  explanation  of  this  great  denuded 
upland,  Button  says  that  the  evidence  points  decisively  to  a 
"period  of  quiescence"  in  Tertiary  time;  "while  it  prevailed, 
the  great  Carboniferous  platform  was  denuded  of  most  of  its  in- 
equalities, and  was  planed  down  to  a  very  flat  expanse  "  (77).  The 
supposition  of  a  period  of  active  uplift,  during  which  the  incision 
of  valleys  was  begun,  and  a  period  of  quiescence,  during  which 
the  hills  were  worn  away,  "  would  give  just  such  a  country  as  we 
see  at  present  "  (225).  Inasmuch  as  the  platform  is  now  in  process 
of  active  destruction  by  the  widening  of  the  main  and  branch 
canons,  a  strong  uplift  must  be  postulated  after  the  period  of 
quiescence  during  which  the  platform  was  denuded.  In  all  this 
inquiry,  the  argument  based  on  processes  of  denudation  is  fully 
as  logical  and  as  legitimate  as  the  argument  elsewhere  based  on 
the  processes  of  deposition. 

But  it  has  never  been  my  intention  to  imply  an  absolute 
stillstand  of  the  earth's  crust  during  an  entire  cycle  of  denuda- 
tion. Any  sort  of  movement  that  does  not  cause  a  distinct  dis- 
section of  the  surface  below  the  peneplain  level  is  admissible. 
Well-preserved  peneplains,  now  dissected  only  by  young,  narrow 
valleys,  give  assurance  that  no  significant  valley  cutting  below 
the  peneplain  level  was  permitted  before  the  uplift  by  which  the 
erosion  of  the  existing  valleys  was  initiated.  Even  in  so  uneven 
a  region  as  southern  New  England  the  gradual  decrease  of  relief 
on  approaching  the  coast  makes  it  extremely  probable  that  the 
deep  valleys  of  the  interior  were  not  cut  till  after  the  peneplain 
was  essentially  finished.  Any  other  supposition  involves  special 
conditions  of  oscillation  and  tilting  that  I  believe  are  less  proba- 
ble than  those  involved  in  peneplanation,  as  may  be  seen  by 
drawing  a  series  of  diagrams  to  represent  the  successive  attitudes 
assumed  by  the  land  under  different  hypotheses. 

It  is  sometimes  suggested  that  before  peneplanation,  but  after 
valleys  like  those  of  southern  New  England  had  been  excavated, 
economy  of  work  and  time  would  be  served  by  postulating  a 


THE  PENEPLAIN  367 

depression  and  a  truncation  of  so  much  of  the  mountains  as 
then  remained  above  base-level.  The  truncated  surface  thus 
produced  would,  under  this  supposition,  correspond  to  the  New 
England  uplands. ,  This  truly  effects  an  economy  of  work, 
measured  by  area  of  base-leveling,  but  it  effects  no  important 
economy  of  time ;  for  it  will  require  essentially  as  long  a  time  to 
truncate  or  base-level  a  large  cone  as  a  small  cone,  structure  and 
slope  being  equal.  Moreover,  unless  very  special  suppositions 
were  made  as  to  the  attitude  of  the  land  before,  during,  and 
after  such  a  truncation  of  its  mountains,  the  existing  forms  of 
southern  New  England  could  not  be  explained.  During  a  sub- 
mergence long  enough  to  truncate  the  mountains  remaining 
above  base-level,  many  shallow  valleys  would  be  filled  with 
marine  deposits  ;  and  after  elevation,  the  streams  might  fre- 
quently abandon  their  former  valleys  for  new,  superposed  courses. 
The  narrow,  new  valleys  excavated  on  such  courses,  and  the 
former  valleys  in  which  remnants  of  marine  deposits  might  long 
linger,  are  not  represented  in  southern  New  England. 

Yet  any  supposition  or  process  that  will  aid  in  the  destruction 
of  a  land  mass  must  be  welcomed  by  those  who  believe  that  land 
masses  have  been  destroyed,  close  down  to  base-level.  The 
lateral  swinging  of  large  rivers,  occasional  incursions  of  the  sea, 
changes  of  climate,  anything  that  will  contribute  to  the  end,  is 
a  pertinent  part  of  the  theory  of  peneplanation.  Still  my  own 
opinion  is  that,  of  all  processes,  sub-aerial  denudation  is  the  most 
important.  This  is  not  simply  an  opinion  of  preference  :  it  is  an 
opinion  based  on  the  arrangement  of  rivers  in  uplifted  and  dis- 
sected peneplains  (Davis,  378-398).  Such  rivers  frequently 
exhibit  adjustments  that  they  could  not  have  gained  from  a  dis- 
ordered arrangement  during  the  present  cycle  of  denudation 
alone ;  adjustments  that  could  have  been  gained  for  the  most 
part  only  during  the  cycle  of  peneplanation,  and  that  would  have 
been  lost  if  the  rivers  had  wandered  far,  or  if  the  sea  had  abraded 
much  of  the  land  during  the  later  stages  of  that  cycle.  It  is  of 
course  perfectly  possible  that  a  peneplain  should  be  smoothed  off 
by  the  sea  after  it  had  been  worn  down  under  the  air :  such 
appears  to  have  been  the  case  with  the  Cambro-Silurian  plain  of 
northwest  England  (see  63);  but  it  is  not  reasonable  to  suppose 


368  PHYSIOGRAPHIC  ESSAYS 

that  every  uplifted  and  dissected  peneplain  was  thus  smoothed 
before  it  was  uplifted,  although  this  supposition  finds  much  favor 
with  certain  English  geologists. 

As  to  the  arguments  based  on  the  slow  progress  of  denuda- 
tion during  a  brief  period  of  observation  or  during  post-glacial 
time,  I  can  only  reply  that  a  geographical  cycle  must  be  so 
enormously  longer  than  either  of  these  intervals  that  their  evi- 
dence is  not  of  value.  Truly,  denudation  is  retarded  when  a 
capping  of  waste  protects  the  rocks  from  the  attack  of  the 
weather,  but  rather  than  side  with  Deluc,  who  concluded  that 
waste-covered  mountains  are  practically  protected  from  further 
change,  I  should  prefer  to  side  with  Hutton,  who  maintained 
that  even  the  slow  denudation  of  waste-covered  slopes  could 
produce  great  changes  of  form.  As  to  the  time  that  has  elapsed 
during  the  denudation  of  dissection  of  peneplains,  there  is 
apparently  no  way  of  measuring  it  but  by  the  work  done. 
Hence  the  question  returns  to  the  verity  of  the  peneplains ; 
whether  much  or  little  time  is  needed  to  produce  them  is  a 
secondary  matter.  Above  all,  a  preconception  as  to  the  insuffi- 
cience  of  geological  time  should  not  in  this  day  be  urged  as  a 
reason  for  not  believing  in  the  possibility  .of  peneplanation. 
One  sometimes  hears  a  student  say :  "  I  should  think  that 
drumlin  ought  to  be  more  eroded  if  it  has  stood  there  unpro- 
tected since  the  ice  sheet  disappeared."  Evidently  such  an 
opinion  is  based  on  a  preconception  of  too  long  a  post-glacial 
interval ;  for  how  can  the  interval  be  measured  except  by  what 
has  happened  to  the  drumlin  during  its  passage  !  How  can  past 
time  be  estimated  except  by  studying  what  has  happened  during 
the  progress  of  its  ages  ! 

B  3 .  No  Part  of  the  Earth  reveals  even  an  Approximation  to  a 
Peneplain.  It  has  been  contended  that  as  all  the  reputed  pene- 
plains now  known  are  of  the  past,  and  that  as  all  are  now  more 
or  less  fragmentary,  "no  part  of  the  earth  reveals  even  an 
approximation  to  this  supposed  condition."  This  seems  to  me 
an  over-strong  statement  in  view  of  the  form  of  such  districts 
as  the  Piedmont  belt,  above  referred  to ;  but  leaving  aside  even 
the  best  examples  of  well-finished  and  slightly  dissected  pene- 
plains, let  us  consider  some  examples  of  peneplains  that  were 


THE  PENEPLAIN  369 

submerged  and  unconformably  buried  after  their  surface  had  been 
reduced  to  faint  relief,  and  that  are  now  more  or  less  visible 
where  valleys  are  cut  into  the  compound  mass  in  consequence 
of  uplift.  It  is  true  that  these  peneplains  are  not  to-day  stand- 
ing in  the  position  in  which  they  were  formed,  that  they  make  a 
very  small  part  of  the  earth's  actual  surface,  and  that  they  are 
imperfectly  open  to  observation;  but  it  seems  to  me  that  they 
give  strong  evidence  of  the  verity  of  peneplains,  and  that  they 
certainly  suffice  to  set  against  the  strong  assertion  quoted  at  the 
opening  of  this  paragraph. 

An  excellent  example  of  a  plain  of  denudation  is  exposed  in 
section  on  the  walls  of  the  Colorado  canon.  It  is  well  shown 
—to  those  who  cannot  see  the  canon  itself — in  several  photo- 
graphs by  Jackson;  it  is  "the  record  of  a  long  time  when  the 
region  was  dry  land,"  as  already  quoted  from  Powell;  and  it  is 
thus  described  by  Button : 

The  base  of  the  Carboniferous  has  a  contact  with  unconformable  rocks 
beneath,  which  was  but  slightly  roughened  by  hills  and  ridges.  In  the 
Kaibab  division  of  the  Grand  canon  ...  we  may  observe  ...  a  few 
bosses  of  Silurian  strata  rising  higher  than  the  hard  quartzitic  sandstone 
which  forms  the  base  of  the  Carboniferous.  These  are  Paleozoic  hills, 
which  were  buried  by  the  growing  mass  of  sediment.  But  they  are  of  insig- 
nificant mass,  rarely  exceeding  two  or  three  hundred  feet  in  height  (209). 

This  magnificent  exposure  of  an  unconformity  is  further  re- 
ferred to  as  a  local  illustration  of  the  widespread  erosion  of  a 
great  mass  of  land,  "afterwards  submerged."  As  the  canon 
has  an  accidental  position  with  regard  to  the  buried  surface,  the 
single  section  may  be  taken  as  a  fair  sample  of  a  much  larger 
area  than  is  actually  exposed. 

A  buried  plain  of  remarkably  even  form  underlies  the  heavy 
Carboniferous  limestones  of  northwestern  England.  It  has  been 
1  repeatedly  described  and  figured  by  English  geologists.  An 
official  report  states : 

It  is  evident  that  these  [Carboniferous]  beds  were  deposited  on  an 
uneven  floor  of  the  Silurian  rocks,  for  the  line  dividing  the  two  formations 
runs  sharply  up  or  down  20  or  30  feet  in  places,  while  the  bedding  of  the 
limestone  keeps  nearly  horizontal.  In  other  places  .  .  .  Silurian  grit  sticks 
up  in  a  boss,  against  the  west  side  of  which  limestone  has  been  laid  down 
in  horizontal  strata  (Dakyns  et  al.,  23). 


370  PHYSIOGRAPHIC  ESSAYS 

The  inequalities  of  the  floor  here  referred  to  are  very  small  in 
comparison  to  the  heights  that  the  Silurian  strata  must  have 
reached  after  their  great  deformation,  for  the  sections  represent 
the  contact  surface  by  an  essentially  even  line,  parallel  to  the 
limestone  beds,  and  so  it  may  be  seen  on  various  valley  sides ; 
for  example,  in  upper  Ribblesdale.  The  actual  contacts  displayed 
in  certain  hillside  quarries  on  Moughton  fell  are  extraordinarily 
clear ;  one  of  them  is  well  reproduced  in  the  frontispiece  to  Bird's 
" Geology  of  Yorkshire."  The  heavy  Silurian  flagstones  are  so 
evenly  truncated  that  a  single  layer  of  limestone  stretches 
smoothly  over  them  for  a  hundred  feet  or  more  across  the 
quarry ;  the  same  limestone  bluff  may  be  traced  for  two  or 
three  miles  around  the  side  of  the  fell,  close  above  the  upper- 
most outcrops  of  the  flagstones;  and  the  same  general  division 
of  the  Carboniferous  formation  lies  on  the  denuded  surface  over 
tens  or  scores  of  miles.  As  there  is  no  residual  soil  on  the  firm 
rocks  of  the  denuded  plain,  and  as  the  overlying  strata  are  heavy 
marine  limestones  (excepting  local  deposits  of  pebbly  beds,  one 
or  two  feet  thick),  the  floor  must  have  been  swept  and  worn  by 
the  sea  before  Carboniferous  deposition  began.  There  seems 
to  be  no  way  of  determining  how  much  work  was  thus  done  by 
the  sea,  and  how  much  had  been  previously  done  by  sub-aerial 
agencies ;  but  whatever  the  proportions,  a  well-finished  plain  of 
denudation,  hundreds  of  square  miles  in  area,  had  taken  the 
place  of  a  vigorous  mountain  range  before  the  deposition  of  the 
limestones  began. 

Goodchild  has  repeatedly  referred  to  this  ancient  plain  of 
denudation,  and  to  two  others  of  later  date  in  northwest  Eng- 
land. He  says  that  when  the  deformed  Cambrian  and  Silurian 
rocks  "were  brought  within  the  destroying  action  of  the  waves 
.  .  . ,  the  end  of  it  was  that  the  whole  surface  of  the  country 
was  shorn  off  to  one  general  uniform  level ;  depressions  and 
elevations  there  were,  beyond  a  doubt,  just  as  there  are  both 
depths  and  islands  left  on  a  modern  plain  of  denudation;  but  in 
the  main  the  surface  was  tolerably  uniform  "  (a,  92,  93).  Many 
mountain  slopes  in  the  Lake  district  consist  of  reexposed  areas 
of  this  ancient  plain,  from  which  the  weaker  covering  strata  have 
been  worn  off  again  (b,  76).  The  plain  extends,  locally,  with 


THE  PENEPLAIN  371 

'marvelous  evenness  of  contour,  across  the  edges  of  quite  five 
miles  of  strata  in  the  Lake  district  alone  (c,  45). 

B  4.  Stratigraphic  Evidence  is  against  the  Occurrence  of  Pene- 
plains. It  has  been  said  that  quiescence  sufficient  for  peneplana- 
tion  requires  conditions  different  from  "  those  of  that  portion  of 
the  past  whose  history  has  been  worked  out  by  purely  strati- 
graphic  methods."  Although  I  am  not  sure  of  just  what  is 
meant  by  "purely  Stratigraphic  methods,"  it  seems  fair  to  regard 
the  two  examples  given  in  the  preceding  section  as  dependent 
on  at  least  a  mixed  Stratigraphic  argument.  These  examples 
were,  however,  associated  with  marine  strata,  and  hence  the  sub- 
aerial  origin  of  the  buried  plains  is  not  assured,  although  there 
can  be  little  doubt  as  to  the  actual  occurrence  of  the  plains  them- 
selves. The  following  examples  are  more  pertinent  to  the  present 
discussion,  for  they  point  chiefly  to  the  action  of  sub-aerial  denu- 
dation in  the  production  of  peneplains. 

The  central  plateau  of  France  is  a  part  of  the  ancient  Her- 
cynian  mountain  system  of  post-Carboniferous  deformation  that 
once  stretched  across  west-central  Europe.  Judging  by  the 
strength  of  its  foldings,  its  altitude  may  for  a  time  have  rivaled 
that  of  the  Alps  of  to-day.  The  mountains  were  greatly  denuded 
during  secondary  time,  as  is  shown  by  the  comparatively  even 
overlaps  of  Jurassic  and  Cretaceous  strata  on  the  flanks  of  the 
central  plateau  and  elsewhere ;  but  of  these  buried  portions  no 
more  need  be  said  at  present.  Continued  denudation  at  last 
reduced  the  region  of  the  central  area  itself  to  a  surface  of 
moderate  relief,  and  it  was  upon  a  surface  thus  prepared  that 
several  brackish  Tertiary  lakes,  communicating  with  the  sea  on 
the  north  and  south,  laid  down  their  sediments.  Since  then, 
the  region  as  a  whole  has  been  much  uplifted,  its  southern  and 
eastern  parts  have  been  irregularly  dislocated,  volcanic  action 
has  diversified  parts  of  the  surface,  and  denudation  has  effected 
important  changes  in  the  complex,  uplifted  mass ;  but  the  north- 
western part  is  free  from  dislocation  and  from  volcanic  action, 
and  there  the  uplifted  surface  of  denudation  is  well  displayed  in 
an  even  plateau  (Deperet).  If  stripped  of  its  volcanic  cones  and 
flows  and  "unfaulted"  the  plateau  would  have  the  form  of  a 
vast  inclined  plane,  highest  in  the  southeast,  and  descending  very 


372  PHYSIOGRAPHIC  ESSAYS 

slowly  to  the  northwest  (Boule).  The  northwestern  part  of  the 
plateau,  unaffected  by  volcanic  action  and  not  covered  by  the  lacus- 
trine formations  that  elsewhere  rest  upon  it,  exhibits  a  surface 
of  crystalline  rocks  interrupted  only  by  closely  folded  troughs  of 
coal  measures,  whose  outcrops  are  sharply  cut  across  at  plateau 
height  as  if  the  whole  structure  had  been  rubbed  down  by  a 
great  leveling  machine.  The  perfect  regularity  of  the  uplands 
between  Montlugon  and  Creuse  is  an  excellent  representation 
of  the  form  that  the  whole  extent  of  the  plateau  region  must 
have  had  about  the  beginning  of  Tertiary  time,  before  it  was 
uplifted  and  dislocated.  Long-continued  erosion  had  then  re- 
duced the  region  to  a  plain  close  to  sea-level,  thus  destroying  a 
great  mountain  chain  and  leaving  in  its  place  a  lowland  com- 
posed chiefly  of  long  belts  of  granitic  rocks  (Velain). 

These  extracts  make  it  clear  that  French  observers  regard 
the  stratigraphic  evidence  of  the  Tertiary  lake  deposits  as  con- 
firming the  conclusion  reached  from  the  study  of  form  alone; 
both  lines  of  evidence  show  that  the  uplifted,  dislocated,  and 
dissected  plateau  region  of  to-day  was  a  lowland  of  denudation 
in  Tertiary  time. 

The  highlands  of  the  Ardennes  along  the  border  of  France 
and  Belgium  is  another  part  of  the  ancient  Hercynian  range, 
greatly  denuded.  It  descends  southward,  where  it  is  overlapped 
by  Mesozoic  formations,  among  which  the  Cretaceous  strata  are 
of  special  interest  in  the  present  connection.  A  belt  of  coal 
measures  extends  from  the  Ardennes  southwestward  under  the 
Cretaceous  ;  shafts  have  been  sunk  through  the  Cretaceous  to 
the  coal  measures  at  many  points,  and  thus  the  form  of  the 
buried  denuded  surface  has  been  determined  with  much  accuracy. 
Gosselet's  elaborate  "Memoire  sur  1'Ardenne  "  (a)  gives  much 
information  concerning  both  the  buried  and  the  unburied  por- 
tions of  the  denuded  mountains.  The  frontispiece  shows  the 
valley  of  the  Meuse  incised  in  the  plateau,  "  everywhere  leveled 
to  the  same  altitude."  Many  sections  in  the  text  show  the  Meso- 
zoic strata  lying  on  the  deformed  and  denuded  Paleozoic  rocks, 
but  the  basal  deposits  beneath  the  Cretaceous  are  usually  not 
marine.  Even  under  the  Jurassic  there  is  a  ferruginous  clay  with 
limonite  concretions,  thought  to  be  of  terrestrial  origin  (802). 


THE  PENEPLAIN  373 

Under  the  Cretaceous  strata  the  most  general  deposit  is  a  layer 
of  black  pyritous  clay  with  vegetal  remains,  taken  to  represent 
the  soil  of  a  pre-Cretaceous  land  surface.  Fluviatile  and  lacus- 
trine deposits  are  also  recognized.  The  Carboniferous  limestone 
is  often  pitted,  and  the  pits  contain  non-marine  materials  and 
fossils.  Where  the  intermediate  deposits  are  wanting,  the  ancient 
rocks  are  perforated  by  boring  mollusks  and  strewn  with  shells 
of  oysters  and  serpulae  (808,  810).  On  the  uplands  at  a  consider- 
able altitude,  and  far  beyond  the  main  overlap  of  the  Mesozoic 
cover,  there  are  scattered  remnants  of  Cretaceous  and  Tertiary 
deposits,  and  these  are  all  regarded  as  of  earlier  date  than  the 
elevation  and  dissection  of  the  plateau  (831).  Fuller  details  as 
to  the  composition  and  distribution  of  these  deposits  are  given 
in  other  papers  by  Gosselet  (b,  100)  and  Barrois  (340).  Bertrand 
says  that  the  buried  pre-Cretaceous  surface  is  a  denuded  plain,  and 
that  its  existing  irregularities  are  due,  at  least  in  great  part,  to 
subsequent  movements  that  the  chalk  also  has  suffered  (36). 

The  different  parts  of  the  ancient  mountains  of  the  Ardennes, 
overlapped  by  Triassic,  Jurassic,  Liassic,  Cretaceous,  and  Terti- 
ary formations,  were  doubtless  exposed  to  denudation  for  different 
periods  of  time,  and  successively  submerged  in  encroaching 
seas ;  it  is  quite  possible  that  the  dissected  uplands  of  to-day 
were  peneplained  at  a  distinctly  later  date  than  was  the  floor 
beneath  the  Jurassic  strata,  and  that  the  relation  of  the  two  is 
similar  to  the  relation  stated  by  Darton  for  the  two  parts  (AB 
and  BE,  Fig.  7)  of  the  ancient  rocks  of  the  Piedmont  belt  in 
Virginia.  French  writers  do  not  seem  to  have  occupied  them- 
selves especially  with  this  question,  either  in  the  Ardennes  or  in 
the  central  plateau.  But,  on  the  other  hand,  there  seems  to  be 
no  question  that  the  stratigraphy  of  both  the  marine  and  the 
terrestrial  deposits  proves  the  existence  in  northern  France  of  a 
denuded  surface  of  small  relief,  whose  larger  part  is  now  buried, 
and  whose  smaller  part  is  elevated  and  more  or  less  dissected. 

Bohemia  offers  another  remarkably  good  example  for  citation, 
as  summarized  by  Penck  and  here  freely  rendered.  A  great 
mountain  range  once  rose  there,  probably  reaching  an  altitude 
of  five  thousand  meters.  It  was  worn  down  to  a  comparatively 
even  lowland  before  the  incursion  of  the  Cretaceous  sea,  by 


374  PHYSIOGRAPHIC  ESSAYS 

whose  deposits  it  is  now  thinly  covered,  for  fresh-water  forma- 
tions are  everywhere  found  under  the  Cretaceous  strata.  This 
relation  is  repeated  in  many  other  parts  of  Europe,  especially 
where  truncated  old  mountains  are  found.  Terrestrial  formations 
are  their  first  cover,  and  upon  these  rest  the  later  marine 
deposits.  It  follows  from  this  that  the  truncated  mountains 
of  Europe  were  not  denuded  by  the  surf  of  ancient  seas,  eating 
into  their  heights  and  gradually  wearing  them  away ;  for  before 
the  sea  rolled  over  the  old  mountains  they  were  already  laid  low 
and  covered  with  terrestrial  formations  (a,  23,  24). 

While  it  may  be  true  that  there  are  to-day  no  extensive  pene- 
plains still  standing  close  to  the  sea-level  with  respect  to  which 
they  were  denuded,  the  examples  given  in  this  and  in  the  pre- 
ceding section  seem  to  me  to  prove  that  the  earth  contains  many 
approximations  to  the  peneplain  condition,  inasmuch  as  it  pre- 
serves some  excellent  fossil  peneplains ;  and  that  the  strati- 
graphic  as  well  as  the  physiographic  method  of  investigation 
yields  abundant  and  accordant  evidence  of  their  occurrence. 

B  5.  Plains  of  Marine  Abrasion  as  well  as  of  Sub-aerial  Den- 
udation are  Discarded.  It  is  worth  while  to  point  out  explicitly 
that  all  these  districts  which  have  been  for  half  a  century  past 
explained  as  uplifted  and  dissected  plains  of  marine  denudation 
(or  of  marine  abrasion)  by  geologists  and  geographers  in  many 
parts  of  the  world  are  to  be  otherwise  interpreted  by  those  who 
adopt  the  alternative  theory  stated  below  (C  2).  The  even  sky 
line,  discordant  with  structure,  has  been  the  leading  evidence  for 
plains'  of  marine  denudation  ever  since  it  was  introduced  by 
Ramsay  in  his  description  of  the  hills  and  mountains  of  South 
Wales.  The  marinists  and  the  sub-aerialists  differ  as  to  the 
agency  by  which  an  elevated  region  may  be  worn  down  to  a 
nearly  featureless  plain,  a  little  below  or  a  little  above  sea-level ; 
but  they  are  unanimous  in  recognizing  the  necessity  of  such 
plains  when  uplands  of  even  sky  line  exist  in  regions  of  disor- 
dered structure.  It  must  be  remembered  that  the  terms  "  plain  of 
marine  denudation  "  and  "peneplain"  are  in  nearly  all  cases  hardly 
more  than  different  names  for  the  same  thing.  If  the  whole 
truth  were  known,  it  is  probable  that  one  or  the  other  name  might 
be  appropriately  applied  in  this  or  that  case,  but  it  is  seldom 


THE  PENEPLAIN 


375 


that  any  one  has  succeeded  in  convincing  all  his  contemporaries 
that  he  could  distinguish  a  plain  of  marine  denudation  from  a 
peneplain,  or  vice  versa.  On  the  other  hand,  all  regions,  hereto- 
fore explained  as  having  passed  through  the  condition  of  abraded 
or  denuded  plains,  would  be  explained  as  never  having  reached  a 
form  of  faint  relief,  if  the  alternative  theory  be  accepted.  It  there- 
fore demands  careful  consideration,  to  which  we  may  now  turn. 

C  i.  The  Alternative  Theory  aims  chiefly  to  explain  the  Exist- 
ing Forms  of  New  England  rather  than  those  of  Better- Finished 
and  Better-Preserved  Peneplains.  It  is  a  matter  of  regret  that  a 
theory  intended  to  replace  the  theory  of  peneplanation  should 
have  been  tested  by  its  author  chiefly  in  New  England,  whose 
highest  and  most  rugged  parts  are  generally  taken  as  examples 
of  grouped  monadnocks.  I  should  not  be  at  all  disposed  to  say 
that  the  peneplains  of  New  England  and  New  Jersey  have  been 
most  fully  studied,  and  rest  upon  the  firmest  basis.  Southern 
New  England  would  have  been  a  fairly  satisfactory  area,  but 
when  the  White  and  Green  mountains  and  the  mountains  of 
Maine  are  included,  the  example  to  be  explained  falls  largely 
outside  of  the  scope  of  peneplanation.  However, -if  the  alter- 
native theory  of  mature  dissection  is  really  capable  of  supple- 
menting the  theory  of  peneplanation,  it  should  suffice  to  explain 
not  only  rugged  New  England,  but  also  the  many  better-finished 
and  better-preserved  peneplains  in  other  parts  of  the  world,  some 
of  which  have  been  referred  to  above. 

C  2.  The  Sub-equality  of  Mountain  Heights.  The  develop- 
ment of  a  rough  equality  in  the  height  of  mountain  peaks  by 
the  faster  destruction  of  the  higher  summits,  on  account  of  the 
greater  violence  of  weather  changes  and  of  the  absence  of  tree 
and  soil  covering  at  great  heights,  has  been  announced  by  Penck 
(&)  and  by  Dawson,  and  has  recently  been  independently  sug- 
gested by  Professor  Tarr.  ABC  and  ADE  (Fig.  8)  are  in  this 
way  changed  to  FGH and  FJK.  The  processes  appealed  to  are 
not  identical  in  the  explanations  of  the  three  authors,  but  not 
having  the  writings  of  the  two  former  at  hand,  I  cannot  give 
details.  The  approach  to  equal  height  of  many  peaks  of  dif- 
ferent structure  in  a  given  mountain  group  may  be  thus  ex- 
plained, as  in  the  Alps,  or  in  the  Rocky  mountains  of  Colorado; 


376 


PHYSIOGRAPHIC  ESSAYS 


if  any  one  felt  per  contra  convinced  that  this  sub-equality  might 
be  the  result  of  the  deep  dissection  of  a  greatly  elevated  pene- 
plain, the  discussion  would  doubtless  be  interesting. 

The  sub-equality  of  mountain  heights  being  once  gained,  all 
the  mountains  are  then  under  essentially  uniform  climatic  con- 
ditions, and  for  the  rest  of  their  lives  difference  of  structure  will 
determine  their  rate  of  decay.  All  changes  would  truly  be  very 
slow,  but  small  differences  in  rate  of  wasting  would  suffice  to 
develop  distinct  differences  of  altitude  while  the  mountains  were 
worn  down  from  the  tree  line  to  the  farm  line.  The  uneven  hill 
and  mountain  districts  about  lake  Winnepesaukee,  New  Hamp- 
shire, might  be  evolved  in  this  way ;  but  it  seems  to  me  very 


FIG.  8 

doubtful  whether  any  such  equality  of  height  as  prevails  in 
central  Massachusetts  can  be  explained  as  an  inheritance  from 
an  equality  determined  by  climatic  control  when  the  regipn  had 
a  much  greater  elevation,  for  to-day  these  uplands  are  about 
three  thousand  feet  below  the  tree  line,  and  their  structure  is 
by  no  means  uniform. 

C  3 .  Denudation  and  Beveling  will  be  more  Advanced  near  the 
Coast  than  in  the  Interior.  It  has  been  urged  that  near  the  coast 
"  mountains  would  have  been  more  lowered  than  in  the  interior, 
and,  in  the  coastal  region,  there  may  well  have  been  an  approach 
to  the  peneplain  condition  "  and  again,  that  "  this  beveling  of  the 
hill-tops  would  be  very  much  further  advanced  near  the  coast 
than  in  the  interior,  thus  coinciding  with  the  conditions  found 
in  New  England." 

The  ancient  mountain  trends  of  southern  New  England  are 
obliquely  traversed  by  the  shore-line  of  Long  Island  sound. 
The  ancient  mountain  structures  show  no  sign  of  weakening  as 
they  approach  the  shore-line,  and  we  may  fairly  suppose  that 


THE  PENEPLAIN  377 

there  has  been  about  as  much  denudation  to  be  done  there  as 
farther  north.  From  southern  New  Hampshire,  across  central 
Massachusetts  and  Connecticut,  there  is  no  indication  of  a  weak- 
ening of  the  rocks  ;  a  good  variety  of  more  or  less  resistant 
gneisses  and  schists  occur  all  across  this  district.  Difference  of 
climate  cannot  be  appealed  to  as  a  cause  of  faster  denudation 
and  beveling  near  the  coast,  for  the  climate  is  more  severe  in 
the  interior.  The  streams  are  larger  and  the  valleys  are  neces- 
sarily lower  and  broader  near  the  coast  than  in  the  interior,  but 
the  interstream  uplands  are  under  essentially  similar  conditions 
in  the  two  regions.  A  rough  equality  of  mountain  heights  being 
established,  as  H,  A,  B  (tig.  9),  there  is  then  no  reason  for  the 
greater  action  of  the  weather  on  a  square  foot  of  surface  at  B 
than  at  A.  The  master  streams  having  gained  a  graded  slope 


FIG.  9 

GEF,  there  is  no  reason  for  the  denudation  of  A  to  hesitate  at 
the  height  C,  a  thousand  feet  above  the  streams,  while  B  is 
reduced  to  D,  only  a  hundred  feet  or  less  above  the  streams. 
The  tilting  of  a  previously  denuded  surface  seems  a  relatively 
simple  and  safe  way  of  accounting  for  the  relation  of  the  upland 
and  stream  profiles  CD  and  EF,  as  has  been  suggested  above 
(A  6);  but  tilting  has  no  announced  place  in  this  alternative 
theory.  The  omission  of  so  commonplace  a  movement*"is  the 
more  curious,  inasmuch  as  frequent  movement  of  some  sort 
must  be  characteristic  of  a  theory  that  requires  no  long  periods 
of  relative  quiet. 

C  4.  New  England  and  New  Jersey  as  Maturely  Dissected 
Mountains,  Rejuvenated.  It  has  been  maintained  that  the  re- 
gions especially  under  discussion  have  been  lowered  to  the  stage 
of  full  maturity,  then  elevated  and  made  more  rugged,  and  that 
although  the  surface  has  always  been  mountainous,  it  was  once 
less  mountainous  than  now,  because  of  the  recent  uplift.  There 
are  various  other  parts  of  the  world  to  which  a  similar  description 


378 


PHYSIOGRAPHIC  ESSAYS 


FIG. 10 


might  be  applied  :  the  indication  of  full  maturity  being  found  in 
the  well-opened  valleys  of  the  larger  streams  ABC  (Fig.  10), 
developed  with  respect  to  a  former  base-level  MM ;  and  the  indi- 
cation of  "recent  uplift"  being  no  less  apparent  in  the  narrow 

gorges  £>,  in- 
cised in  the 
floor  of  the  ma- 
turely opened 
valleys  ABC, 
with  reference 

to  the  new  base-level  NN.  The  essential  evidence  of  such  recent 
uplift  and  rejuvenation  is  found  in  benches  E,  F,  on  the  compound 
valley  slopes  AED  and  CFD.  If  rejuvenation  were  so  long  ago 
that  this  bench  were  destroyed  by  the  development  of  continuous 
slopes  AGD  and  CHD,  then  the  uplift  could  not  be  discovered 
by  topographical  evidence.  It  is  on  evidence  of  this  kind  that 
rejuvenation  has  been  announced  for  the  Susquehanna  district 
of  the  Pennsylvania  Appalachians  and  for  the  Hudson  valley  ; 
but  no  description  has  been  published  of  any  such  evidence  for 
the  rejuvenation  of  New  England.  The  deep  valleys  of  many 
rivers  in  Massachusetts  and  Connecticut  have  no  persistent 
benches  on  their  slopes,  and  there  is  no  visible  reason  for  say- 
ing that  any  important  pause  was  made  in  the  elevation  by  which 
the  former  base-level  of  the  uplands  A  C  was  replaced  by  the  pres- 
ent base-level  NN  oi  the  valleys  AGDHC.  The  rivers  truly  have 
many  falls  and  rapids,  due  to  their  displacement  from  better- 
graded  courses  by  the  irregular  distribution  of  glacial  drift,  but 
this  is  quite 
another  matter. 
The  valley- 
side  benches 
are  important 
items  in  the 

present  discussion,  if  they  exist  at  all ;  for  when  fully  established 
they  will  define  many  interesting  points.  If  high  on  the  valley 
sides,  as  at  A  (Fig.  1 1)  (resembling  the  gorge  of  the  Rhine),  they 
would  show  that  the  previous  cycle  had  gone  far  beyond  maturity 
and  well  into  old  age  before  uplift  occurred  ;  if  low  down  in  the 


FIG.  ii 


THE  PENEPLAIN  379 

valley  bottom,  as  at  B  (resembling  the  Fraler  river  valley  in 
British  Columbia),  they  are  of  trifling  importance  as  far  as  the 
present  discussion  is  concerned.  If  the  downstream  slope  of  the 
benches  were  about  parallel  to  the  present  profile  of  the  rivers, 
a  uniform  uplift  would  be  suggested ;  if  distinctly  not  parallel  to 
the  present  stream  profiles,  an  uneven  uplift  would  be  implied. 
All  these  points  should  receive  specific  attention  if  the  new 
hypothesis,  which  "requires  no  long  periods  of  relative  quiet,"  is 
to  be  accepted.  As  now  stated,  the  recent  rejuvenation  of  New 
England  seems  to  me  very  open  to  question.  There  is  no  evi- 
dence of  recent  rejuvenation  in  the  occurrence  of  a  young 
coastal  plain  along  the  coastal  border,  such  as  ordinarily  accom- 
panies recent  uplift,  unless  the  post-glacial  coastal  plain  of  Maine 
be  so  considered  ;  and  that  would  hardly  be  permissible,  for  the 
existing  valleys  were  eroded  before  the  plain  was  formed. 

C  5.  The  Alternate  Hypothesis  takes  no  Account  of  Buried 
Peneplains.  The  alternative  hypothesis,  which  calls  merely  for 
a  greatly  reduced,  but  still  markedly  irregular  surface,  entirely 
fails  to  meet  the  case  of  well-preserved  peneplains,  like  that  of 
the  Piedmont  belt  in  Virginia,  and  even  more  entirely  fails  to 
meet  the  case  of  buried  peneplains,  such  as  have  been  described 
above.  The  first  example  cited  —  that  of  the  even  floor  on 
which  the  Carboniferous  rocks  rest  in  the  Colorado  canon  —  is 
entirely  beyond  the  reach  of  a  theory  that  does  not  carry  sub- 
aerial  denudation  farther  than  the  stage  of  maturity.  If  refuge 
is  taken  in  the  theory  of  marine  abrasion,  the  several  examples 
in  France  and  Bohemia,  where  marine  abrasion  is  excluded, 
remain  to  be  explained.  It  must  therefore  be  repeated  that  it  is 
a  matter  of  regret  that  a  theory  intended  to  supplant  the  theory 
of  peneplanation  should  have  been  framed  chiefly  with  respect 
to  the  rugged  uplands  of  New  England  and  New  Jersey,  and 
without  sufficient  consideration  of  the  many  other  examples  of 
better  peneplains,  buried  and  unburied,  of  which  modern  geolog- 
ical and  geographical  writings  contain  abundant  descriptions. 

The  preparation  of  this  essay  has  been  greatly  aided  by  the 
kindness  of  my  geological  and  geographical  colleagues  in  Edin- 
burgh, London,  and  Paris.  The  completion  of  the  essay  in  south- 
eastern France  has  made  it  impossible  to  cite,  as  fully  as  I  should 


380  PHYSIOGRAPHIC  ESSAYS 

like,  certain  pertinent  examples,  to  which,  however,  there  may  be 
opportunity  of  returning  if  fuller  consideration  of  the  peneplain 
idea  is  called  for  by  a  continuation  of  this  discussion. 

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Velain,  C.    "Auvergne  et  Limousin,  Geographic  Physique."     L'ltineraire 
Miriam,  10.    Paris,  1897. 


XVIII 
BASE-LEVEL,   GRADE,   AND   PENEPLAIN 

Thesis  of  this  Essay.  The  attention  given  during  the  last  fifty 
years  to  the  processes  and  results  of  land  sculpture  has  naturally 
resulted  in  the  introduction  of  various  new  terms,  three  of  which 
stand  at  the  head  of  this  article.  It  is  desired  to  point  out  that 
too  many  meanings  have  been  attached  to  the  first  term,  "  base- 
level,"  and  that  some  of  them  should  be  transferred  to  the  other 
two,  "grade"  and  "peneplain." 

The  Original  Meaning  of  Base-Level.  Although  the  control 
exerted  by  sea-level  on  river  action  has  long  been  recognized, 
the  importance  of  the  control  was  more  generally  perceived  by 
American  students  of  geology  when  it  was  explicitly  formulated 
in  the  term  "base-level"  by  Powell  in  1875.  The  term  soon  be- 
came so  popular,  especially  with  American  writers,  that  a  diver- 
gence of  meaning  has  arisen  with  regard  to  it.  It  is  therefore 
proposed  to  trace  its  history,  with  the  hope  of  inducing  geologists 
and  geographers  to  use  it  in  a  somewhat  restricted  sense. 

Powell's  original  definition  of  base-level  is  as  follows,  the 
parenthesis  being  in  his  text : 

We  may  consider  the  level  of  the  sea  to  be  a  grand  base-level,  below 
which  the  dry  lands  cannot  be  eroded  ;  but  we  may  also  have,  for  local  and 
temporary  purposes,  other  base-levels  of  erosion,  which  are  the  levels  of  the 
beds  of  the  principal  streams  which  carry  away  the  products  of  erosion.  (I 
take  some  liberty  in  using  the  term  "level"  in  this  connection,  as  the  action 
of  a  running  stream  in  wearing  its  channel  ceases,  for  all  practical  purposes, 
before  its  bed  has  quite  reached  the  level  of  the  lower  end  of  the  stream. 
What  I  have  called  the  base-level  would,  in  fact,  be  an  imaginary  surface, 
inclining  slightly  in  all  its  parts  toward  the  lower  end  of  the  principal  stream 
draining  the  area  through  which  the  level  is  supposed  to  extend,  or  having 
the  inclination  of  its  parts  varied  in  direction  as  determined  by  tributary 
streams.)  Where  such  a  stream  crosses  a  series  of  rocks  in  its  course,  some 
of  which  are  hard,  and  others  soft,  the  harder  beds  form  a  series  of  tempo- 
rary dams,  above  which  the  corrasion  of  the  channel  through  the  softer  beds 


382  PHYSIOGRAPHIC  ESSAYS 

is  checked,  and  thus  we  may  have  a  series  of  base-levels  of  erosion,  below 
which  the  rocks  on  either  side  of  the  river,  though  exceedingly  friable,  can- 
not be  degraded  (a,  203,  204). 

Base-level,  as  thus  defined,  seems  to  include  three  ideas : 
first,  the  grand  or  general  base-level  for  sub-aerial  erosion  is  the 
level  of  the  sea ;  second,  a  base-level  is  an  imaginary,  sloping 
surface  which  generalizes  the  faint  inclination  of  the  trunk  and 
branch  rivers  of  a  region  when  the  erosion  of  their  channels  has 
practically  ceased ;  third,  local  and  temporary  base-levels  are 
those  slow  reaches  in  a  river  which  are  determined  by  ledges  in 
its  course  farther  downstream. 

There  is  some  reason  for  thinking  that  Powell's  intention  may 
have  been  misunderstood  with  respect  to  the  first  and  third  of 
these  ideas.  The  first,  "the  level  of  the  sea,"  may  have  referred 
only  to  the  actual  area  of  the  sea,  and  not  to  an  imaginary  exten- 
sion of  the  sea-level  or  geoid  surface  under  the  lands.  The  third 
certainly  referred  to  the  faintly  sloping  reach  of  a  river,  and  not  to 
a  level  surface  passing  through  the  ledge  of  hard  rock  with  respect 
to  which  the  reach  is  worn  down,  although  this  latter  meaning  has 
become  popular.  The  following  citations  will  show  that  most 
writers  seem  to  be  agreed  that  base-levels  may  be  local  or  tempo- 
rary as  well  as  general,  but  that  there  is  no  prevalent  agreement 
as  to  the  definition  of  either  the  general  or  the  local  base-level. 

Definitions  of  Base-Level  by  Various  Writers.  The  following 
authors  adopt  the  first  of  the  above  meanings.  Gilbert  writes  : 
"The  land  cannot  be  worn  down  below  the  level  of  the  ocean. 
Geologists  express  this  law  by  saying  that  the  ocean  is  the  '  base- 
level  of  erosion'  "  (c,  575). 

Campbell  says  :  "  If  the  streams  are  in  their  old  age,  the  sur- 
face of  the  land  will  constitute  a  peneplain,  and  in  their  extreme  old 
age,  this  peneplain  will  approach  very  closely  to  base-level"  (665). 

Tarr  writes  to  the  same  effect :  "  In  no  part  of  the  valley  can 
the  stream  cut  below  the  sea-level,  or  below  base-level,  as  it  is 
called  "  (265). 

Russell  quotes  Powell,  as  if  adopting  his  definition,  but  con- 
cludes that 

the  real  base-level  toward  which  all  streams  are  working  is  the  surface 
level  of  the  sea.  .  .  .  When  a  stream  has  lowered  its  channel  nearly  to 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  383 

base-level,  downward  corrasion  is  retarded,  but  lateral  corrasion  continues. 
.  .  .  The  ultimate  result  of  erosion  is  to  reduce  a  land  area  to  a  plain  at  sea- 
level  (47-48). 

Finally,  Powell  may  be  quoted  again  as  follows  :  "  The  base- 
level  of  a  plain  is  the  level  of  the  surface  of  the  sea,  lake,  or 
stream  into  which  the  waters  of  the  plain  are  discharged"  (£,  34). 

The  second  idea  under  the  term  "  base-level "  -that  of  the 
imaginary,  undulating  surface  —  does  not  appear  to  have  been 
adopted  by  any  of  the  many  writers  whose  works  I  have  looked 
over.  It  is  perhaps  on  account  of  the  elaborateness  of  this  sec- 
ond meaning  that  it  has  not  come  more  generally  into  use.  Its 
partial  adoption,  however,  is  indicated  by  the  following  extracts. 
It  should  be  noted  that  nearly  all  the  writers  here  cited  imply 
that  after  base-level  is  reached  by  a  stream,  downward  corrasion 
ceases. 

McGee  describes  the  streams  of  the  coastal  plain  at  about  the 
head  of  Chesapeake  bay  as  "at  base-level"  (a,  617). 

When  describing  the  dissection  of  the  Piedmont  plateau  of 
Virginia,  Darton  says :  "As  the  cutting  reached  base-level  a 
series  of  wide  terraces  were  cut"  (584). 

Winslow  writes:  "The  streams  of  the  prairie  country  [in 
Missouri]  .  .  .  have,  in  large  part,  reached  base-level,  and  are 
developing  meander  plains  (310). 

Fairbanks  states  that  in  southeastern  California 

erosion  has  reached  an  advanced  stage  with  the  production  of  excellent 
examples  of  base-leveling.  .  .  .  One  of  the  best  examples  ...  is  the 
western  portion  of  a  granite  ridge  lying  south  of  the  El  Paso  range.  ...  It 
is  bordered  by  long,  gentle  slopes  of  gravel  and  bowlders,  which,  extending 
upward  into  the  shallow  canons,  reach  almost  to  the  summit.  Viewed  from 
a  distance  of  ten  miles  but  little  of  the  mountains  appears  to  project  above 
the  plane  of  deposition  (70). 

Salisbury's  statement  is  as  follows : 

The  time  necessary  for  the  development  of  such  a  surface  is  known  as 
a  cycle  of  erosion,  and  the  resulting  surface  is  a  base-level  plain,  that  is,  a 
plain  as  near  sea-level  as  river  erosion  can  bring  it.  At  a  stage  preceding 
the  base-level  stage  the  surface  would  be  a  peneplain.  ...  It  is  also  impor- 
tant to  notice  that  when  streams  have  cut  a  land  surface  down  to  the  level 
at  which  they  cease  to  erode,  that  surface  will  still  possess  some  slight  slope, 
and  that  to  the  seaward.  Along  the  coast  a  base-level  is  at  sea-level.  A 


384  PHYSIOGRAPHIC  ESSAYS 

little  back  from  the  coast  it  is  slightly  higher,  and  at  a  greater  distance  still 
higher.  No  definite  degree  of  slope  can  be  fixed  upon  as  marking  a  base- 
level.  The  angle  of  slope  which  would  practically  stop  erosion  in  a  region 
of  slight  rainfall  might  be  great  enough  to  allow  of  erosion  if  the  precipi- 
tation were  greater.  .  .  .  The  Mississippi  has  a  fall  of  less  than  a  foot  per 
mile.  ...  A  small  stream  in  a  similar  situation  would  have  ceased  to  lower 
its  channel  before  so  low  a  gradient  had  been  reached  (£,  73,  79). 

J.  Geikie  writes  : 

Running  waters  will  continue  to  deepen  their  channels  until  the  gradient 
by  the  process  is  gradually  reduced  to  a  minimum  and  vertical  erosion 
ceases.  The  main  river  will  be  th^  first  to  attain  this  base-level,  —  a  level 
not  much  above  that  of  the  sea  (47). 

Marr  does  not  use  the  term  "base-level,"  but  says : 

A  river  which  has  established  equilibrium  ...  is  said  to  have  reached 
its  base-line  of  erosion,  and  no  further  work  of  erosion  or  deposit  can  occur 
until  the  conditions  are  changed  (84). 

Dryer  states  : 

The  lower  Mississippi  has  reached  its  base-level,  or  the  lowest  level  to 
which  its  current  and  load  will  permit  it  to  reduce  its  bed.  ...  In  the 
lower  reaches  of  a  river  the  valley  is  soon  cut  down  to  base-level,  where  the 
slope  is  gentle  and  the  current  too  slow  to  carry  the  full  load  of  sediment 
it  receives.  Deposition  occurs  and  downward  corrasion  ceases  (79,  154). 

•  In  a  discussion  of  reaches  and  rapids  Powell  makes  the  follow- 
ing statement :  "  The  slow  reach  is  a  base-level,  like  that  of 
a  lake,  below  which  the  banks  and  hills  on  either  side  cannot  be 
degraded"  (ft  35). 

Various  other  definitions,  more  or  less  aberrant  from  the  original 
and  discordant  with  each  other,  are  found  in  the  following  citations. 

Button  took  base-level  to  be  a  condition  : 

The  condition  of  base-level  is  one  in  which  the  rivers  of  a  region  cannot 
corrade.  As  a  general  rule  it  arises  from  the  rivers  having  cut  down  so 
low  that  their  transporting  power  is  fully  occupied,  even  to  repletion.  .  •.  . 
The  recurrence  of  upheaval  terminates  the  condition  of  base-level  (224,  225). 

According  to  Willis,  base-level  is  a  slope : 

A  base-level  is  the  lowest  slope  to  which  rivers  can  reduce  a  land  area 
(a,  189).  The  ideal  lowest  possible  slope,  which  is  called  a  base-level,  is 
perhaps  rarely  reached  (^,  27). 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  385 

Hayes  makes  base-level  a  mathematical  plane  : 

The  term  "  base-level,"  synonymous  with  base-level  of  erosion,  is  [here] 
restricted  to  Powell's  original  use  .  .  . ,  the  general  base-level  being  sea-level. 
There  may  be  an  indefinite  number  of  local  base-levels  in  any  region,  each 
being  determined  by  the  outlet  of  the  stream  whose  drainage  basin  is  con- 
sidered ;  but  only  one  general  base-level.  ...  It  should  be  clearly  under- 
stood, then,  that  a  base-level  is  not  a  topographic  form,  but  a  mathematical 
plane  which  may  or  may  not,  and  generally  does  not,  coincide  with  a  land 
surface  (21). 

When  describing  erosion  by  rivers,  Scott  writes : 

A  stage  must  sooner  or  later  be  reached  when  the  vertical  cutting  of  the 
stream  must  cease.  This  stage  is  called  the  base-level  of  erosion  or  regimen 
of  the  river,  and  it  approximates  a  parabolic  curve,  rising  toward  the  head 
of  the  stream  (98). 

Rice  makes  the  following  statement :  "  The  condition  of  balance 
between  erosion  and  deposition  [by  rivers]  has  been  called  by 
Powell  the  condition  of  base-level"  (140). 

Brigham  writes  as  follows  : 

A  base-level  is  a  plane  to  which  denudation  must  reduce  a  stably  poised 
land  mass,  and  below  which  denudation  cannot  take  place.  The  plane  is 
that  of  the  ocean  surface.  .  .  .  The  great  river  first  cuts  its  bed  close  to 
the  sea-level,  and  we  say  that  a  portion  of  the  valley  is  reduced  to  base-level. 
It  lacks  a  little  of  it,  but  the  difference  is  so  small  that  we  neglect  it. 
Gradually  the  valley  widens,  and  the  base-leveled  strip  extends  up  the 
stream  toward  the  heart  of  the  country  (281). 

Cowles  gives  a  definition  of  base-level  which,  taken  literally, 
gives  it  the  meaning  of  a  process  :  "  Denudation  of  the  uplands 
and  deposition  in  the  lowlands  result  in  an  ultimate  planation 
known  as  the  base-level "  (178). 

The  derivative  use  of  base-level  as  the  name  of  a  worn-down 
land  surface  does  not  seem  to  be  so  common  now  as  it  was  some 
ten  years  ago.  A  few  examples  will  here  suffice. 

Keith  made  frequent  use  of  "base-level  plain,"  or  simply  " base- 
level,"  as  the  name  for  a  surface  that  had  been  reduced  to  faint 
relief,  even  though  now  uplifted  and  more  or  less  dissected.  He 
discusses  the  "  considerable  variation  in  the  altitude  of  different 
parts  of  the  base-level"  or  old  Tertiary  land  surface  in  the  Catoctin 
region  district  of  Virginia  (373).  He  mentions  "  hill  tops  marking 
the  dissected  base-level"  of  the  Shenandoah  valley  (374).  The 


386  PHYSIOGRAPHIC  ESSAYS 

term  seems  to  be  applied  in  at  least  one  instance  to  a  peneplain 
in  saying,  "  It  needs  but  little  study  of  this  base-level  to  discover 
considerable  inequalities  in  its  surface"  (369). 

Diller  made  equally  free  use  of  "base-level-plain"  and  of  "base- 
level"  in  his  account  of  an  ancient  surface  of  erosion  in  northern 
California.  He  states  that  "  the  western  edge  of  the  base-level, 
where  it  enters  the  mountains,  has  an  altitude  of  2600  feet,"  and 
on  a  later  page  he  suggests  two  ways  in  which  the  "  deformation 
of  the  base-level  may  be  studied  "  (406,  430). 

Kummel  writes  of  the  "long  erosion  which  resulted  in  the 
Cretaceous  base-level "  of  Connecticut  (379). 

Willis  says : 

The  tendency  is  in  time  to  reduce  the  land  to  a  gently  sloping  plain, 
which  extends  from  the  sea  to  the  headwaters  of  the  rivers.  Such  a  plain 
is  called  a  base-level.  ...  A  surface  which  is  almost,  but  not  quite,  a 
base-level  is  called  a  peneplain  (a,  188,  189). 

Hill  describes  a  persistent  bench  near  Panama  as  "  represent- 
ing an  ancient  base-leveled  plain,  which  will  be  described  as  the 
Panama  base-level"  (197). 

An  essay  by  Van  Hise  describing  a  base-leveled  plain  is  en- 
titled "A  Central  Wisconsin  Base-Level"  (57). 

I  have  had  a  small  share  in  a  similar  use  of  base-level ;  for 
example : 

The  general  upland  surface  of  the  Highlands  [of  New  Jersey]  is  an  old 
base-level,  in  which  valleys  have  been  cut  in  consequence  of  a  subsequent 
elevation  (a,  20  ;  see  also  Davis  and  Wood,  384). 

A  review  of  the  above  citations,  whose  number  might  be 
greatly  extended,  shows  that  base-level  is  given  very  different 
meanings  by  different  writers.  These  meanings  are :  an  imagi- 
nary level  surface  in  extension  of  that  of  the  ocean  (the  convex 
geoid  surface)  ;  an  imaginary  mathematical  plane ;  an  imaginary 
surface  sloping  with  the  mature  or  old  streams  of  its  area ;  the 
lowest  slope  to  which  rivers  can  reduce  a  land  surface  ;  a  level 
not  much  above  that  of  the  sea ;  a  slow  reach  in  a  stream  ;  a 
condition  in  which  rivers  cannot  corrade  or  in  which  they  are 
balanced  between  erosion  and  deposition  ;  a  certain  stage  in 
the  history  of  rivers  when- vertical  cutting  ceases  and  their  slope 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  387 

approximates  a  parabolic  curve  ;  an  ultimate  plariation ;  and  a 
plain  of  degradation. 

Limitation  of  the  Meaning  of  Base-Level.  The  diversity  of 
the  above  definitions  may  be  better  perceived  when  it  is  noted 
that  they  are  expressed  in  terms  of  very  unlike  quantities  :  imagi- 
nary surfaces,  level,  plane,  or  warped  ;  a  low  slope  ;  a  part  of  a 
river  ;  a  condition  of  river  development ;  a  stage  in  river  history  ; 
an  ultimate  planation ;  and  an  actual  geographical  form.  It  is 
evidently  desirable  to  associate  base-level  with  at  most  only  a 
few  of  these  meanings,  preferably  with  only  one ;  and  to  leave 
the  others  unnamed,  or  to  associate  them  with  other  terms.  It 
seems  to  me  advisable  to  limit  base-level  to  the  first  meaning, 
"an  imaginary  level  surface,"  and  to  define  it  simply  as  the  level 
base  with  respect  to  which  normal  sub-aerial  erosion  proceeds  ;  to 
employ  the  term  "grade  "  for  the  balanced  condition  of  a  mature 
or  old  river ;  and  to  name  the  geographical  surface  that  is  devel- 
oped near  or  very  near -to  the  close  of  a  cycle,  a  "peneplain,"  or 
"plain  of  gradation."  The  following  paragraphs  may  make  the 
need  of  this  discrimination  clearer. 

A  full  understanding  of  the  development  of  land  forms  can  be 
gained  only  by  tracing  the  progressive  changes  of  a  generalized 
example  from  the  initial  stage  through  the  various  sequential 
stages  to  the  ultimate  stage  of  an  ideal  geographical  cycle.  This 
problem  is  encountered  in  an  elementary  form  at  the  beginning 
of  the  study  of  land  sculpture  in  physiography  or  geology,  and  at 
the  very  outset  it  is  necessary  to  make  definite  and  simple  state- 
ment regarding  the  limit  with  respect  to  which  the  processes  of 
normal  sub-aerial  erosion  (weather  and  streams,  without  significant 
aid  from  wind  or  ice)  may  act.  If  the  limit  is  defined  in  terms  of 
the  slopes  that  the  streams  of  the  region  will  have  gained  when 
they  have  reached  a  maturely  balanced  condition,  the  definition 
will  be  of  no  service  to  beginners ;  indeecl,  a  limit  thus  defined  is 
elusive  and  difficult  of  conception  even  by  experts.  The  limiting 
surface  is  certainly  of  so  great  importance  to  the  beginner  that 
it  must  be  briefly  defined  for  him  in  terms  of  known  factors,  and 
the  definition  thus  framed  should  remain  serviceable  through  all 
later  study.  These  conditions  are  satisfied  when  the  beginner  is 
told  that  the  limit  of  sub-aerial  erosion  is  the  "level  base"  or 


388  PHYSIOGRAPHIC  ESSAYS 

" base-level"  drawn  through  a  land  mass  in  prolongation  of  the 
normal  sea-level  surface.  The  fact  that  rivers  erode  their  chan- 
nels near  their  mouths  below  sea-level,  and  that  special  processes 
of  erosion  (winds  and  glaciers)  may  work  below  sea-level,  does  not 
invalidate  the  general  statement  at  the  opening  of  the  whole  dis- 
cussion ;  but  these  special  conditions  must  be  explicitly  considered 
later,  especially  those  concerning  glacial  erosion.  It  suffices  at 
first  to  recognize  that  in  the  ideal  undisturbed  cycle  of  normal 
erosion  the  base-level  must  be  more  and  more  closely  approached 
as  time  is  extended. 

This  definition  of  base-level  as  a  level  base  certainly  has  the 
advantage  of  being  easily  conceived.  Once  conceived  in  the  study 
of  the  ideal  cycle,  it  needs  no  modification  so  long  as  the  relative 
attitude  of  land  and  sea  remains  fixed.  If  the  land  rise  or  fall  with 
respect  to  the  sea,  the  base-level  takes  a  new  position  within  the 
land  mass,  and  further  progress  of  erosion  is  then  continued  with 
respect  to  the  new  limit. 

As  the  study  of  the  cycle  advances  it  becomes  desirable  to 
speak  of  various  local  or  temporary  controls  of  erosion :  a  rock 
ledge  or  a  lake  on  a  river  course,  the  central  basin  of  a  dry  interior 
basin  either  above  or  below  sea-level,  the  surface  of  a  lake  in  such 
a  basin.  Nothing  can  be  simpler  than  to  imagine  a  level  surface 
passing  through  any  one  of  these  controls,  and  rising  or  sinking 
as  the  control  rises  or  sinks  ;  and  such  a  surface  is  naturally  called 
a  local  or  temporary  base-level.  With  the  enlargement  of  concep- 
tions that  is  required  when  the  aggradation  of  depressions  is 
considered  at  the  same  time  with  the  degradation  of  elevations, 
Powell's  more  general  term  "  gradation"  may  replace  " erosion"; 
the  merit  of  this  substitution  will  appear  more  fully  in  the 
following  pages. 

In  view  of  the  importance  appropriately  allowed  to  the  idea  of 
the  level  base  with  respect  to  which  the  erosion  of  valleys  by 
rivers  must  proceed,  it  is  curious  that  earlier  writers  did  not  give 
more  explicit  attention  to  it ;  but  as  far  as  I  have  read,  they  were 
so  largely  occupied  with  controverting  the  various  older  theories 
of  the  origin  of  valleys  that  it  did  not  occur  to  them  to  give  spe- 
cial name  to  limiting  surface  of  erosion.  Their  understanding  of 
the  important  principle  here  involved  is  to  be  read  rather  between 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  389 

the  lines  than  in  explicit  statements.  For  example,  Greenwood's 
curious  book  on  "  Rain  and  Rivers,"  almost  as  remarkable  for 
its  admixture  of  jokes  and  polemics  as  for  its  many  admirable 
expositions  of  rain  and  river  work,  contains  the  following  account 
of  the  problems  here  considered  : 

Suppose  a  barrier  of  rock  to  run  across  any  valley  or  river  bed ;  when 
the  bed  of  the  valley  or  river  on  the  upper  side  of  the  barrier  has  been 
worn  down  to  a  horizontal  level  with  this  barrier,  it  can  not  go  lower.  .  .  . 
But  as  the  barrier  is  cut  through,  the  bed  of  the  valley  or  river  will  be 
deepened  backward,  or  from  below  upward,  or  towards  the  hills.  .  .  .  The 
passage  of  the  detritus  and  soil  from  the  inclined  upper  parts  of  valleys  is 
checked  in  the  horizontal  lower  parts  of  valleys,  and  soil  accumulates  there. 
This  is  the  origin  of  alluvial  plains  ;  and  a  river  of  any  size,  or  any  rapidity, 
may,  at  any  distance  from  the  sea,  have  patches  of  alluvial  plain,  where  no 
lakes  have  ever  been ;  that  is,  above  every  rapid  or  accidental  barrier  of 
hard  ground.  .  .  .  The  only  difference  in  the  laws  for  the  growth  and 
gradient  of  these  patches  from  those  which  regulate  the  growth  and  gradi- 
ent of  the  plain  at  the  level  of  the  sea  is  that  they  have  no  increasing 
cause  for  rising  equivalent  to  the  forward  lengthening  of  the  delta  of  the 
lower  alluvial  plain.  These  flat,  alluvial  patches  may  be  seen  even  in  tor- 
rents, sometimes  reaching  from  one  cascade  to  the  other.  ...  It  is  easy 
to  perceive  that  these  patches  must  be  liable  to  constant  change.  They 
must  be  perpetually  shortened  by  the  recession  of  the  lower  barrier,  and 
lengthened  by  the  recession  of  the  upper  one.  .  .  .  These  principles  are 
eternally  at  work  on  all  valleys,  from  the  smallest  to  the  largest  (174-176). 

Greenwood's  use  of  "  horizontal  "  in  describing  the  lower  parts 
of  valleys  is  curiously  inexact  in  contrast  to  his  keenness  in 
recognizing  the  difference  between  what  we  should  now  call 
local  base-levels  and  general  base-levels,  and  also  in  recognizing 
that  the  aggradation  of  a  flood  plain  is  related  to  the  "  forward 
lengthening  of  the  delta." 

The  Balanced  Condition  of  Rivers.  Turning  now  more  particu- 
larly to  the  problem  of  river  action,  we  find  that  the  balance 
between  erosion  and  deposition,  attained  by  mature  rivers,  intro- 
duces one  of  the  most  important  problems  that  is  encountered  in 
the  discussion  of  the  geographical  cycle.  The  development  of  this 
balanced  condition  is  brought  about  by  changes  in  the  capacity 
of  a  river  to  do  work,  and  in  the  quantity  of  work  that  the  river 
has  to  do.  The  changes  continue  until  the  two  quantities,  at  first 
unequal,  reach  equality ;  and  then  the  river  may  be  said  to  be 


390  PHYSIOGRAPHIC  ESSAYS 

graded,  or  to  have  reached  the  condition  of  grade.  This  condition 
cannot  be  understood  without  rather  careful  thinking  on  the  part 
of  the  expert  as  well  as  of  the  tyro.  The  idea  of  grade  is  not  of 
almost  axiomatic  simplicity,  like  the  idea  of  base-level ;  its  meaning 
must  be  gradually  elaborated  as  it  is  approached.  Moreover,  a 
graded  river  does  not  maintain  a  constant  slope ;  it  changes  its 
slope  systematically  with  the  progress  of  the  cycle ;  but  before 
taking  up  this  element  of  the  discussion,  a  few  paragraphs  may  be 
given  to  the  consideration  of  "grade,"  as  a  common  word  used 
in  a  technical  sense. 

It  should  be  noted  in  the  first  place  that  it  is  a  condition  of 
river  development,  not  a  surface,  nor  a  stage,  nor  a  form,  for 
which  the  term  "  grade  "  is  to  serve  as  a  name.  The  condition 
of  grade  must  not  be  confused  with  the  limiting  under-surface  of 
erosion,  with  respect  to  which  the  graded  condition  is  developed ; 
the  name  for  this  surface  is  "  base-level."  Nor  must  it  be  confused 
with  the  stage  in  the  history  of  river  development  in  which  the 
graded  condition  is  reached;  "maturity"  is  the  name  for  that 
stage  ;  but  it  may  be  noted  in  passing  that  the  graded  condition 
persists  all  through  the  old  age  as  well  as  the  maturity  of  an 
uninterrupted  cycle.  "  Grade,"  meaning  a  condition  or  balance, 
must  not  be  confused  with  the  same  word  used  with  another  mean- 
ing, namely,  the  slope  or  declivity  of  the  river  when  the  graded 
condition  is  reached  ;  for  "grade,"  meaning  slope,  varies  in  place 
and  in  time ;  while  "grade,"  meaning  balance,  always  implies  an 
equality  of  two  quantities.  In  fine,  grade  is  a  condition  of  essen- 
tial balance  between  corrasion  and  deposition,  usually  reached  by 
rivers  in  the  mature  stage  of  their  development,  when  their  slopes 
have  been  duly  worn  down  or  built  up  with  respect  to  the  base- 
level  of  their  basin. 

There  can  be  no  question  that  the  balanced  condition  of  mature 
and  old  rivers  deserves  a  name.  It  was  to  this  condition  that 
Powell  called  attention  in  his  original  discussion  of  land  sculpture, 
and  to  which  he  devoted  one  of  the  meanings  of  his  term  "  base- 
level."  A  name  had  already  been  suggested  for  the  balanced 
condition  by  various  writers,  who  called  it  the  "  regime  "  or  "  regi- 
men "  of  rivers,  while  the  slope  of  a  river  under  this  regimen 
was  called  its  " pente  d'tquilibre"  by  Dausse  (759)  and  the 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  391 

** Erosions-Terminante"  by  Philippson  (71).  But  "regimen  "  may 
be  better  used  as  meaning  the  rule  of  river  action  under  which 
the  balanced  condition  is  developed  and  maintained  ;  while  "  slope 
of  equilibrium  "  may  be  taken  as  a  descriptive  phrase,  too  cum- 
bersome for  ordinary  or  frequent  use,  but  essentially  synonymous 
with  "graded  slope."  "Base-level"  seems  at  best  a  very  inap- 
propriate name  for  a  condition  in  which  the  idea  of  slope  is  essen- 
tial ;  and  when  another  and  equally  important  use  is  made  of  this 
excellent  word,  its  employment  as  the  name  for  the  balanced 
condition  of  rivers  is  all  the  more  unsatisfactory.  "Grade"  is 
the  most  satisfactory  term  for  the  balanced  condition  or  state 
of  equilibrium  of  rivers  on  several  grounds,  in  spite  of  certain 
objections  that  may  be  urged  against  it.  Let  us  consider  the 
objections  first. 

Origin  and  Use  of  the  Term  "  Grade"  One  of  my  correspond- 
ents has  objected  to  "  grade  "  because,  in  the  sense  here  adopted, 
the  word  means,  etymologically,  a  step,  and  not  a  slope.  This 
objection  seems  to  me  of  small  value  on  account  of  the  freedom 
with  which  new  meanings  are  given  to  old  roots.  Language 
does  not  grow  by  rule  but  by  use ;  and  use  has  decreed  that  one 
meaning  of  the  English  word  "grade"  shall  depart  somewhat 
from  the  meaning  of  its  Latin  ancestor.  The  chapter  on  Trans- 
ference of  Meaning,  in  a  work  on  "  Words  and  their  Ways  in 
English  Speech,"  by  two  of  my  colleagues,  Professors  Greenough 
and  Kittredge,  may  be  consulted  to  advantage  in  this  connection. 

Another  correspondent  objects  because  the  word  "grade"  is 
already  in  common  use,  meaning,  among  other  things,  a  slope,  and 
the  ratio  of  the  vertical  to  the  horizontal  in  a  slope  ;  but  as  a  matter 
of  fact  no  practical  inconvenience  has  arisen  on  this  account.  The 
context  suffices  to  indicate  which  one  of  the  several  meanings  of 
the  word  is  intended.  Moreover,  if  we  should  endeavor  to  escape 
the  criticism  of  Scylla,  by  making  up  a  new  technical  term  in 
order  to  avoid  the  technical  use  of  a  common  word  in  a  new 
meaning,  we  should  be  met  by  the  objections  of  Chary bdis, 
who  maintains  that  "every  new  technical  term  is  a  positive 
detriment  .to  science."  The  objections  to  "grade"  seem  to 
me  far  outweighed  by  the  many  points  in  its  favor,  which  may 
now  be  reviewed. 


392  PHYSIOGRAPHIC  ESSAYS 

In  favor  of  the  term  it  may  be  noted  first  that  "grade,"  like 
"  base-level,"  is  of  a  convenient  form,  ready  for  use  as  noun,  adjec- 
tive, and  verb,  after  the  handy  fashion  of  the  English  language 
in  many  other  cases.  In  the  second  place,  the  sense  of  the  verb 
"grade,"  as  employed  by  engineers  (to  prepare,  by  cutting  and 
filling,  a  smooth  bed  of  gentle  slope  for  a  railroad  or  other  line 
of  transportation),  is  closely  analogous  to  the  meaning  here  advo- 
cated for  the  verb  " grade  "  as  used  by  geologists  and  geographers ; 
a  river  grades  its  course  by  a  process  of  cutting  and  filling,  until 
an  equable  slope  is  developed  along  which  the  transportation  of 
its  load  is  most  effectively  accomplished.  In  the  third  place, 
"grade  "  lends  itself  admirably  to  the  formation  of  such  terms  as 
"  degrade,"  "  aggrade,"  and  "  gradation  " ;  "  degrade,"  in  the  sense 
of  to  wear  down,  has  been  in  use  for  some  time  by  geologists ; 
"aggrade"  is  an  excellent  addition  to  our  terminology,  proposed 
by  Salisbury  (a,  103)  in  the  sense  of  building,  up  ;  while  "grada- 
tion "  is  Powell's  term  for  the  general  process  of  wearing  down 
elevations  and  filling  up  depressions,  in  the  production  of  lowland 
plains  (b,  30).  Finally,  the  word  has  already  made  a  beginning 
towards  acquiring  a  useful  place  in  scientific  writings. 

The  use  of  "grade"  in  the  sense  here  advocated  was  almost 
reached  by  Gilbert  in  his  description  of  hills  of  planation,  covered 
with  stream  gravels  :  "  The  slope  of  the  hill  depends  on  the 
grade  of  the  ancient  stream,  and  is  independent  of  the  hardness 
and  dip  of  the  strata  "  (b,  130);-  and  again  in  his  account  of  how 
a  river  "tends  to  establish  a  single,  uniform  grade,"  and  "an 
equilibrium  of  action  "  (a,  100).  It  was  in  consequence  of  a  sug- 
gestion from  this  philosophical  writer  that  I  introduced  "grade" 
as  a  substitute  for  various  paraphrases  in  my  own  work  in  1893 

(b,  77)- 

McGee  considers  the  control  of  the  balanced  condition  of  rivers 
under  the  "law  of  river  gradation"  (b,  265). 

Mill  uses  "grade"  as  a  verb,  essentially  in  the  sense  here 
advocated  :  "  Ultimately  the  river  grades  its  course  and  flows 
uniformly  along  a  uniform  slope  "  (56). 

Gannett  has  adopted  "grade"  as  a  technical  term  in  Folios 
I  and  2  of  the  Topographic  Atlas  of  the  United  States.  In 
the  first  he  writes  :  "  There  finally  comes  a  time  when  the  river 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  393 

ceases  to  erode,  or,  rather,  it  deposits  as  much  as  it  erodes.  .  .  . 
A  river  is  then  said  to  be  graded." 

In  the  second  a  special  sheet,  with  explanatory  text,  is  de- 
voted to  "A  Graded  River,"  the  example  chosen  being  the  lower 
Missouri : 

At  this  stage  the  lower  portion  of  its  [a  river's]  course  has  been  eroded 
to  almost  as  low  a  stage  as  possible,  and  its  slope  has  become  very  slight, 
so  that  its  cutting  power  is  trifling.  This  part  of  the  stream  is  said  to  be 
"  graded." 

Johnson  uses  "  gradation  "  as  involving  both  degradation  and 
aggradation,  and  as  producing  a  "graded  slope,"  a  slope  of  "equi- 
librium easily  disturbed,  yet  constantly  maintained  "  (620). 

"Grade  "  may  therefore  be  regarded  as  having  already  gained 
recognition  in  the  sense  here  advocated,  as  a  replacement  of  one 
of  the  meanings  of  "  base-level." 

There  remain  to  be  considered  several  reasons  in  favor  of  giv- 
ing different  names  to  the  limiting  base  of  sub-aerial  erosion  and 
to  the  balanced  condition  in  which  rivers  spend  most  of  their  lives 
while  approaching  the  limit  of  their  work.  The  first  reason  is 
based  on  the  persistence  of  the  base-level  surface  all  through  the 
cycle,  without  change  from  its  initially  complete  extension,  in 
contrast  to  the  gradual  introduction  and  slow  extension  of  the 
condition  of  grade  during  the  mature  and  older  stages  of  the 
cycle.  The  second  is  based  on  the  fixity  of  the  base-level  surface 
in  contrast  to  the  variation  in  the  slope  of  graded  rivers.  The 
third  springs  from  the  essential  simplicity  in  the  meaning  of 
"base-level"  in  contrast  to  the  complexity  and  variety  of  condi- 
tions ultimately  gathered  under  the  term  "grade." 

Base-Level  is  Complete  from  the  Beginning  and  Permanent  to 
the  End ;  Grade  is  Sloivly  Introduced  and  Gradually  Extended. 
The  conception  of  the  general  base-level  must  be  made  at  the 
outset  as  that  of  a  completed  surface  extending  beneath  the  land 
mass  under  consideration  at  the  beginning  of  the  cycle,  and  so 
remaining  as  long  as  the  advance  of  the  cycle  continues  undis- 
turbed. In  the  ideal  case,  which  provides  the  general  scheme 
with  respect  to  which  all  other  cases  are  classified,  the  land  mass 
once  uplifted  is  supposed  to  stand  still  until  it  is  worn  down  flat. 
This  supposition  is  so  artificial  and  does  so  great  violence  to  much 


394  PHYSIOGRAPHIC  ESSAYS 

that  is  known  as  to  the  behavior  of  the  earth's  crust  that  some 
students  are  therefore  disposed  to  discard  the  scheme  of  the  cycle 
altogether  in  the  study  of  the  sculpture  of  land  masses,  overlook- 
ing the  fact  that  however  many  movements  of  a  land  mass  may 
be  discovered,  the  many  incomplete  cycles  that  are  separated  by 
these  movements  must  each  be  treated  essentially  according  to 
the  scheme  of  the  ideal  cycle.  In  every. case  the  processes  of 
land  sculpture,  quickened  or  slackened  in  consequence  of  the 
new  attitude  given  to  the  region,  go  on  with  respect  to  the  new 
attitude  of  the  base-level  within  the  land  mass. 

Even  during  the  movement  of  the  land  mass,  it  must  be  con- 
ceived of  as  rising  or  sinking  through  a  fixed  and  complete  base- 
level  surface,  with  respect  to  which  its  carving  is  even  then  begun, 
and  long  afterwards  continued,  during  the  ensuing  time  of  rela- 
tive or  absolute  rest.  Hence,  for  every  cycle  or  partial  cycle  of 
erosion,  the  imaginary  base-level  surface  is  immediately  conceived 
as  complete  at  the  outset,  and  as  thenceforwards  remaining  un- 
changed. Local  base-levels  are  also  complete,  in  extending  at 
once  as  far  as  the  imagination  wishes  to  carry  them ;  they  rise 
or  fall  slowly  with  their  control. 

It  is  far  otherwise  with  the  development  of  the  graded  condition. 
The  previous  paragraphs  have  explained  that  the  development  of 
grade  depends  on  the  spontaneous  adjustment  of  the  capacity  of 
a  river  to  do  work,  and  the  quantity  of  work  to  be  done  by  the 
river.  It  is  well  understood  that  this  adjustment  is  realized  by 
the  larger  streams  relatively  early  in  the  cycle ;  by  those  of 
medium  and  smaller  size  at  later  and  later  stages  ;  and  hence 
that  the  condition  of  grade  is  deliberately  introduced  and  system- 
atically extended  through  all  parts  of  a  river  system  as  the  cycle 
advances.  The  condition  of  grade  needs  no  mention  when  the 
scheme  of  the  cycle  is  first  presented.  Truly,  it  might  be  consid- 
ered as  an  accompaniment  of  the  youth  of  a  cycle  in  those  special 
cases  where  a  large  river  is  running  across  a  slowly  rising  region 
of  weak  rocks,  for  here  the  condition  of  grade  may  be  continuously 
maintained  during  the  period  of  uplift.  But  it  is  not  in  connection 
with  special  cases  of  this  kind  that  a  first  acquaintance  with  the 
condition  of  grade  is  best  made.  Its  fuller  meaning  is  not  likely 
to  be  well  understood  unless  presented  with  something  of  the 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  395 

deliberation  that  characterizes  the  actual  development  of  graded 
rivers.  Indeed,  the  conception  of  grade  is  likely  to  be  an  embar- 
rassment if  presented  too  early. 

The  extension  of  the  graded  condition  over  all  parts  of  a  river 
system  introduces  a  thoroughness  of  organization  in  the  processes 
of  land  sculpture  that  warrants  the  use  of  the  term  "  maturity  " 
as  the  name  of  the  stage  of  the  cycle  in  which  the  organization 
of  river  systems  is  chiefly  accomplished.  The  growth  of  organi- 
zation goes  with  the  development  of  grade.  In  every  reach  of  a 
river  in  which  the  graded  condition  has  been  attained,  the  lowest 
point  on  the  reach  is  always  coincident  with  and  dependent  on  a 
controlling  base-level  (as  above  defined),  either  general  or  local, 
and  river  action  at  any  point  in  the  graded  reach  is  then  deli- 
cately correlated  with  that  at  every  other  point.  River  action  in 
such  a  reach  may  justly  be  said  to  be  organized,  inasmuch  as  a 
change  in  form  or  action  at  any  one  point  involves  a  change  at 
every  other  point.  Adjacent  reaches,  separated  by  a  fall  on  an 
ungraded  ledge  or  by  an  unfilled  lake,  are  independently  organ- 
ized ;  a  change  in  one  does  not  necessarily  call  for  a  change  in 
the  other.  But  when  all  falls  and  rapids  are  worn  down,  and  all 
lakes  are  filled  up,  and  the  entire  river  system  is  graded,  as  is 
characteristically  the  case  in  the  late-mature  stage  of  a  cycle,  the 
organization  of  the  system  is  so  complete  that  all  its  parts  are 
correlated.  A  change  at  any  one  point  then  involves  a  change, 
of  infinitesimal  amount  perhaps,  all  through  the  system.  It  is 
this  condition  of  organization  that  Gilbert  alluded  to  in  describ- 
ing the  "interdependence"  that  comes  to  be  developed  among 
the  different  lines  of  a  river  system,  as  a  result  of  which  "  a  dis- 
turbance upon  any  line  is  communicated  through  it  to  the  main 
line  and  thence  to  every  tributary"  (b,  124). 

The  actual  slopes  of  the  different  parts  of  a  graded  river  system 
vary  from  a  faintest  declivity  in  the  lower  course  of  the  trunk 
river  to  decidedly  steeper  declivities  in  the  uppermost  courses  of 
the  headwater  streams.  If  any  stream  line  is  followed  from  head 
to  mouth,  its  profile  will  show  a  curve,  approximating  theoretically 
to  the  flatter  part  of  one  wing  of  a  parabola ;  but  when  studied 
in  detail,  the  normally  continuous  decrease  of  slope  downstream 
is  found  to  be  seldom  realized.  The  entrance  of  a  tributary  is 


396  PHYSIOGRAPHIC  ESSAYS 

usually  accompanied  by  a  decrease  of  slope  upstream  and  an  in- 
crease of  slope  downstream  from  the  tributary  mouth ;  the  spas- 
modic action  of  floods  introduces  some  faint  symptoms  of  disorder 
in  otherwise  simple  slopes  ;  and  in  this  connection  the  inequalities 
due  to  what  McGee  has  called  "  varigradation  "  are  to  be  consid- 
ered (b,  269 ;  see  also  Oldham).  All  these  complications  in  the 
slopes  of  a  graded  river  system  make  it  extremely  difficult  to  con- 
ceive of  a  surface  which  shall  generalize  the  river  slopes.  Indeed, 
it  is  hardly  worth  while  to  attempt  this  conception,  for  the  reason 
that  all  the  value  of  the  imaginary  surface  is  to  be  found  in  the 
actual  slope  lines  of  the  graded  river  systems  by  which  the  sur- 
face is  guided.  It  is  with  respect  to  the  sloping  course  of  a  graded 
stream  that  the  valley  sides  are  to  be  worn  down  ;  it  is  with  re- 
spect to  the  graded  lines  of  a  river  system  that  its  whole  basin  is 
to  be  worn  down.  This  conception,  as  announced  by  Powell,  is 
of  fundamental  importance  ;  but  it  does  not  seem  to  gain  in  clear- 
ness or  strength  by  expressing  the  control  of  erosion  in  terms  of 
a  warped  surface,  guided  by  the  branching  lines  of  the  graded 
river  system,  instead  of  expressing  it  distinctly  in  terms  of  the 
branching  stream  lines  themselves.  Reference  will  be  made  again 
to  this  aspect  of  the  problem  further  on. 

Not  only  do  graded  streams  vary  in  slope  in  different  parts  of 
a  river  system  ;  the  slopes  may  vary  greatly  in  two  neighboring 
river  systems  at  the  time  of  the  general  establishment  of  their 
grade.  This  may  be  illustrated  by  considering  the  unlike  con- 
ditions obtaining  in  two  rivers,  alike  in  volume,  but  one  flowing 
through  an  upland  of  resistant  rocks,  the  other  through  a  similar 
upland  of  weak  rocks.  The  first  river  would  have  to  cut  down  a 
deep  valley  to  a  gentle  slope  before  grade  was  reached,  because  its 
load  would  be  slowly  delivered  from  the  resistant  rocks  of  its 
valley  walls,  and  high  walls  would  have  to  be  produced  by  deep 
valley  cutting  before  a  balance  could  be  struck  between  the  in- 
creasing load  from  the  walls  and  headwaters  and  the  decreasing 
capacity  of  the  river.  The  second  river  could  not  cut  so  deep  a 
valley,  however  weak  the  rocks  of  its  bed,  because  it  would  have 
an  abundant  load  supplied  by  the  rapid  wasting  of  its  valley  sides, 
even  when  they  were  of  moderate  height,  and  a  strong  slope 
down  the  valley  would  be  required  in  order  to  maintain  a  velocity 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  397 

with  which  the  graded  stream  could  bear  the  abundant  load  away. 
Only  as  the  whole  upland  is  worn  down  in  the  later  stages  of  the 
cycle  could  the  second  stream  wear  down  its  valley  to  a  gentle 
slope,  and  then  the  valley  would  be  still  shallower  than  when 
grade  was  first  attained. 

The  principle  here  considered  is  clearly  recognized  by  Gilbert, 
who  instances  the  Platte  as  a  river  of  the  second  kind,  and  states 
that  Powell  also  had  so  described  it  (a,  100).  The  difference 
between  the  two  kinds  of  rivers  is  not  satisfactorily  indicated 
in  terms  of  base-level,  but  it  is  clearly  presented  by  stating  that 
one  has  developed  its  grade  on  a  faint  slope,  the  other  on  a 
stronger  slope. 

The  incapacity  of  the  Platte  to  deepen  its  valley  leads  Gannett 
to  describe  it  as  an  "overloaded  river";  but  this  phrase  is  not 
altogether  satisfactory,  because  it  overlooks  the  fact  that  rivers 
refuse  to  be  overloaded.  A  river  will  most  dutifully  work  up  to 
its  full  capacity  ;  it  is  ready  to  increase  its  capacity  by  increasing 
its  slope  through  aggrading  when  necessary  (as  stated  below),  and 
thus  it  may  become  heavily  loaded  ;  but  like  the  traditional  llama 
it  refuses  to  carry  an  overload.  Like  all  streams  with  braided 
channels,  the  Platte  is  well  graded,  as  well  graded  as  the  typical 
lower  Missouri,  although  the  quantity  and  texture  of  its  load 
require  it  to  maintain  a  relatively  strong  slope. 

Base-Level  remains  fixed  all  through  an  Uninterrupted  Cycle  ; 
the  Slope  of  Graded  Streams  must  vary  as  the  Cycle  advances. 
After  a  river  system  has  attained  a  maturely  graded  condition, 
it  will  maintain  a  graded  condition  through  all  the  rest  of  the 
undisturbed  cycle ;  but  it  is  important  to  recognize  that  the 
maintenance  of  grade,  during  the  very  slow  changes  in  volume 
and  load  that  accompany  the  advance  of  the  cycle,  involves  an 
appropriate  change  of  slope  as  well.  Instead,  therefore,  of  having 
to  do  with  a  fixed  control  of  erosion,  such  as  is  found  in  the 
general  base-level  of  a  region,  we  have  here  to  do  with  a  slowly, 
delicately,  and  elaborately  changing  equilibrium  of  river  action, 
accompanied  by  a  corresponding  change  in  river  slope.  For  ex- 
ample, a  large  river  in  a  mountain  valley  may  reach  grade  in  the 
early  maturity  of  its  region.  It  will  then  flow  with  a  rushing 
current  on  a  rapidly  sloping  bed  of  cobblestones,  and  may  stand 


398  PHYSIOGRAPHIC  ESSAYS 

hundreds  or  even  thousands  of  feet  above  base-level.  In  the  old 
age  of  the  region  the  same  river  will  flow  with  a  sluggish  current 
on  a  nearly  level  bed  of  sand  and  silt  through  a  peneplain,  only 
a  few  tens  or  scores  of  feet  above  base-level. 
•  This  is  a  point  that  is  not  generally  enough  recognized.  It  is 
too  often  implied  —  in  the  absence  of  explicit  statement  to  the 
contrary  —  that  when  a  river  is  once  balanced  between  erosion 
and  deposition  its  slope  thenceforward  remains  constant.  The 
beginner  would  gather  this  understanding  of  the  question  from 
several  of  the  definitions  of  "base-level"  above  quoted,  but  such 
is  evidently  not  the  case.  When  a  stream  is  first  graded,  its 
channel  is  not  level,  and  it  has  not  reached  the  base  of  its  erosive 
work.  In  virtue  of  the  continual,  though  slow,  variations  of  stream 
volume  and  load  through  the  normal  cycle,  the  balanced  condition 
of  any  stream  can  be  maintained  only  by  an  equally  continuous, 
though  small,  change  of  river  slope,  whereby  capacity  to  do  work, 
and  work  to  be  done,  shall  always  be  kept  equal.  It  might  at  first 
be  thought  that  changes  of  this  kind  would  be  perceptible,  and 
that  there  would  be  occasional  departures  of  a  river  from  the 
graded  condition ;  but  such  is  not  the  case,  because  the  change 
in  the  value  of  any  variable  in  a  unit  of  time  is  only  by  a  quantity 
of  the  second  order,  by  a  differential  of  its  total  value.  Once 
graded,  a  river  will  never  depart  perceptibly  from  the  graded  con- 
dition as  long  as  the  normal  advance  of  the  cycle  is  undisturbed. 
The  slope  of  a  river  must  necessarily  be  steeper  on  the  first  attain- 
ment of  grade  in  early  maturity,  when  an  abundant  load  is  received 
from  the  steep  valley  sides  and  the  active  headwaters,  than  in  late 
old  age,  when  the  valley  sides  have  been  worn  down  almost  level, 
and  when  the  even  headwater  streams  are  weak  and  sluggish. 
Hence,  just  as  a  graded  river  has  slopes  of  varying  declivities  in 
its  different  parts  at  any  one  time,  so  the  slope  at  any  one  part 
of  the  river  must  vary  at  different  times  in  the  successive  stages 
of  the  cycle. 

Not  only  so  ;  it  is  eminently  possible  that  the  slope  of  a  graded 
stream  may  have  to  be  increased  for  a  time  after  it  has  been  first 
attained,  for  there  is  no  necessity  that  the  load  should  cease 
increasing  just  when  its  value  has  risen  to  equality  with  that 
which  the  stream  can  transport.  There  is  much  probability  that, 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  3*99 

after  grade  is  reached  in  a  normal,  undisturbed  cycle,  a  river  may 
have  for  a  time  to  aggrade  its  valley  floor  until  the  time  of  maxi- 
mum load  is  reached ;  and  only  after  the  maximum  gives  way  to 
a  decrease  of  load  can  there  be  a  beginning  of  that  very  slow  and 
long-continued  decrease  of  river  slope  which  continues  through 
late  maturity  and  old  age.  Furthermore,  if  at  any  time  in  the 
cycle  a  change  of  climate  should  occur,  new  slopes  would  have 
to  be  developed  by  the  streams  in  order  to  bring  about  a  new 
balance  between  erosion  and  transportation  under  the  new  relation 
of  load  and  volume.  If,  for  example,  the  changes  were  from  humid 
to  arid  conditions,  all  the  valley  floors  would  have  to  be  steepened 
by  aggradation.  If  from  arid  to  humid,  the  graded  valley  floors 
would  be  sharply  trenched,  and  in  time  reduced  to  lower  slopes. 
There  can  be  little  doubt  that  under  an  increased  rainfall  the 
"base-level"  described  in  southeastern  California  by  Fairbanks 
would  be  sharply  dissected,  quite  independent  of  any  elevation 
of  the  region.  I  have  already  discussed  certain  aspects  of  this 
problem  (c,  377). 

The  clearest  account  that  I  have  found  of  the  normal  varia- 
tion of  the  graded  slope  is  in  the  paper  by  Johnson  already  cited. 
He  says  that  the  graded  slope  "continually  alters  its  inclination. 
There  is  a  slow  departure  from  equilibrium,  and  there  is  closely 
following  readjustment  toward  recovery  of  it."  The  graded  slope 
passes  through  its  "  transformations  with  a  slowness  comparable 
to  that  of  mountain  wear.  ...  It  keeps  pace  with  the  slow 
growth  of  the  debris  mass  following  upon  mountain  lowering." 
But  if  a  stream  be  deprived  of  the  greater  part  of  its  load  by  some 
abnormal  changes,  it  "would  at  once  attack  its  former  slope  of 
equilibrium,  and  rapidly,  though  at  a  progressively  slowing  rate, 
lower  it.  On  the  other  hand,  its  load  largely  increased,  the  stream 
would  rapidly  build  up  the  slope.  In  either  case,  however,  it 
would  come  to  a  stand  at  a  new  grade  of  equilibrium"  (621). 

The  same  author  attaches  much  importance  to  the  effect  of 
climatic  changes  on  graded  river  slopes.  When  describing  the 
dissection  of  the  High  plains,  he  says : 

It  is  not  necessary,  in  order  to  account  for  change  in  behavior  of  the 
traversing  streams,  to  appeal  to  deformation.  A  sufficient  cause  may  be 
looked  for  in  change  of  climate.  There  is  record  of  erosion,  with  reversal 


400  PHYSIOGRAPHIC  ESSAYS 

to  deposition  and  rebuilding,  and  reversal  again  finally  to  erosion,  and 
there  is  reason  for  believing  that  this  series  of  interruptions  of  the  grada- 
tion cycle  was  an  effect  of  climatic  oscillation  rather  than  of  earth  move- 
ment (628). 

This  is  by  far  the  most  striking  actual  example  of  varying 
graded  slopes  on  record,  —  an  example  that  is  easily  denned  in 
terms  of  changing  grade,  but  not  in  terms  of  changing  base-level. 
It  is  much  more  satisfactory  to  describe  the  High  plains  in  terms 
of  stronger  or  fainter  graded  slopes  than  to  consider  them  "  near 
base-level,"  as  has  been  done  in  spite  of  their  standing  at  altitudes 
of  four  thousand  feet  and  more. 

The  conception  of  grade  must  therefore  include  the  conception 
of  different  and  changing  slopes  in  large  and  small  streams,  in 
mature  and  old  streams,  in  streams  dissecting  weak  and  strong 
rocks,  in  streams  of  arid  and  humid  regions.  The  conception  is  of 
the  greatest  value  as  a  supplement  to  the  simpler  idea  of  base-level ; 
but  it  is  so  intricate  that  it  cannot  be  fully  apprehended  until  the 
whole  course  of  the  cycle  is  patiently  worked  through.  Yet  a  still 
further  extension  of  the  conception  remains  to  be  considered. 

Base-Levels  are  of  only  Two  Kinds,  General  (Permanent}  and 
Local  ( Temporary] ;  Grade  includes  not  only  the  Balanced  Con- 
dition of  Large  and  Small,  Mature  and  Old  Water  Streams,  but 
that  of  All  Kinds  of  Waste  Streams  as  well.  A  final  reason 
for  giving  different  names  to  the  limiting  base  of  sub-aerial  ero- 
sion and  to  the  balanced  condition  of  the  mature  and  old  streams 
that  are  working  with  respect  to  the  limiting  base  is  found  in  the 
essential  identity  of  conditions  in  graded  water  streams  and  in 
graded  waste  streams,  and  in  the  strong  unlikeness  between  the 
attitude  of  a  base-level  surface  as  defined  in  any  of  the  above 
citations  and  the  slopes  often  assumed  by  graded  waste  streams. 
These  are  points  to  which  the  geologists  and  geographers  of  the 
older  schools  gave  little  or  no  attention ;  indeed,  it  is  only  about 
fifty  years  since  some  of  the  leaders  of  our  science  taught  that 
rounded  hills  could  not  be  formed  by  sub-aerial  erosion  and  that 
they  must  be  the  work  of  the  sea.  It  is  now  well  understood,  how- 
ever, that  slopes  covered  with  soil  of  local  or  up-hill  derivation  are 
really  "  drained  "  by  an  association  of  many  graded  waste  streams, 
whose  behavior  closely  resembles  that  of  graded  water  streams. 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  401 

The  first  development  of  the  balanced  or  graded  condition  in 
waste  streams  usually  takes  place  on  the  outcrops  of  the  weaker 
rocks  that  are  exposed  on  freshly  cut  valley  sides.  Here  graded 
waste  slopes  are  locally  developed ;  the  adjoining  waste  streams 
form  a  sheet  or  cloak  of  waste  which  creeps  slowly  down  the 
slope,  while  untamed  ledges  of  harder  rocks  are  still  kept  bare 
by  the  removal  of  waste  from  their  surface  as  fast  as  it  is  formed. 
These  represent  the  falls  and  rapids  of  water  streams,  because 
the  waste  from  above  the  ledges  passes  over  them  quickly ;  while 
the  graded  waste-covered  slopes  represent  the  graded  reaches  of 
water  streams,  where  the  movement  is  more  regular  and  leisurely. 
The  less  resistant  of  the  bare  ledges  are  the  first  to  retreat  under 
cover,  permitting  the  grades  below  and  above  to  unite  in  a  single 
continuous  slope,  and  so  on,  until  all  ledges  are  concealed  under 
a  graded  sheet  of  waste,  and  the  sharp,  vigorous  forms  of  youth 
and  early  maturity  merge  into  the  subdued  and  tamed  forms  of 
passing  maturity  and  approaching  old  age.  During  the  progress 
of  this  change  there  may  be  abundant  examples  of  captures  of 
one  group  of  waste  streams  by  the  leading  members  of  another 
group,  especially  in  regions  of  tilted  strata,  thus  increasing  the 
resemblance  of  waste  streams  and  water  streams,  until  one  is 
tempted  to  regard  the  difference  between  them  as  one  of  degree 
rather  than  of  kind. 

As  maturity  passes  into  old  age,  all  the  elevations  are  worn  lower 
and  lower  and  the  graded  cloak  of  waste  covers  more  and  more 
of  the  surface.  As  the  later  stages  of  the  cycle  are  approached, 
the  whole  region,  monadnocks  excepted,  is  reduced  to  moderate 
relief,  and  bare  ledges  are  rarely  seen.  On  the  faintly  sloping 
forms  of  advanced  old  age  the  graded  sheet  of.  waste  covers  the 
entire  surface  between  the  water  streams.  Everywhere  gently 
waste-covered  slopes  lead  from  the  low  arched  divides  to  the 
streams.  The  surface  soil,  greatly  refined  in  texture  by  long 
exposure  to  the  weather  in  its  deliberate  journey,  slowly  creeps 
and  washes  to  the  streams,  and  the  relief  is  reduced  to  smaller 
and  smaller  measures.  The  condition  of  grade,  at  first  developed 
in  the  lower  course  of  the  larger  rivers,  next  in  their  branches 
and  headwaters,  then  on  the  valley  sides  and  over  the  hills,  has 
thus  been  extended  all  over  the  region.  The  organization  that 


402  PHYSIOGRAPHIC  ESSAYS 

at  maturity  characterized  the  water  streams  has  come  in  old  age 
to  characterize  the  streams  and  sheets  of  waste  all  over  the  land 
surface.  From  the  beginning  to  the  end  of  this  process  there  is 
steady  progress  without  break  or  interruption  through  the  normal 
cycle.  There  is  an  essential  unity  of  development  through  the 
whole  of  it.  It  is  very  desirable  that  this  unity  should  be  ex- 
pressed in  the  terms  employed  in  the  description  of  land  sculpture 
and  land  form,  and  that  the  balanced  condition  of  water  streams 
and  waste  streams  alike  should  be  expressed  by  such  a  term  as 
"grade,"  rather  than  that  an  artificial  distinction  between  them 
should  be  introduced  by  speaking  of  the  balanced  rivers  as 
defining  a  "  base-level,"  while  balanced  waste  streams  are  given 
some  other  name  by  which  their  close  affinity  to  graded  water 
stream  is  concealed. 

An  old  land  surface,  sheeted  over  with  a  graded  soil  cover,  is  a 
peneplain  of  erosion  or  of  gradation  ;  it  passes  slowly  into  a  plain 
of  gradation.  It  is  almost  the  realization  of  that  imaginary  base- 
level  surface  described  by  Powell  as  "  inclining  slightly  in  all  its 
parts  toward  the  lower  end  of  the  principal  streams  draining  the 
area  through  which  the  level  is  supposed  to  extend,  or  having  the 
inclination  of  its  parts  varied  in  direction  as  determined  by  tribu- 
tary streams  " ;  but  this  imaginary  surface  is  elusive  and  intangible, 
because  of  the  impossibility  of  defining  the  stage  of  stream  devel- 
opment when  it  should  be  introduced,  and  the  length  of  graded 
stream  course  that  it  should  follow ;  while,  on  the  other  hand,  the 
graded  land  surface  is  a  reality  whose  gradual  development  and 
slow  change  is  one  of  its  essential  characteristics. 

Until  the  imaginary  surface  is  thus  realized,  it  is  hardly  worth 
while  to  attempt  to  conceive  it,  for  as  far  as  the  control  of  ero- 
sive processes  is  concerned,  that  is  better  exercised  (as  has  been 
stated  already)  by  the  visible  skeleton  of  the  surface  that  is  seen 
in  graded  streams  than  by  the  surface  itself.  It  is  always  with 
reference  to  the  graded  course  of  the  main  river  that  the  side 
streams  are  graded  ;  it  is  with  reference  to  all  the  graded  streams 
that  the  slopes  of  the  interfluves  are  graded.  These  relations  of 
branch  to  trunk  and  of  side  slopes  to  streams  are  of  the  very 
greatest  importance  and  must  be  considered  with  the  utmost 
care  ;  but  the  imaginary  surface  passing  from  river  to  river  under 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  403 

the  hills  of  the  interfluves  has  relatively  little  importance  as  a 
control  of  the  processes  of  erosion.  With  every  extension  head- 
wards  along  the  graded  channels  of  branching  streams,  the  surface 
becomes  more  warped  and  wrinkled,  more  difficult  to  conceive, 
more  likely  to  differ  as  conceived  by  different  minds.  It  must  be 
not  only  irregularly  warped  when  first  defined,  but  it  must  vary 
slowly  in  form  and  slope.  Just  as  no  limit  can  be  set  to  the  head- 
ward  part  of  the  graded  main  stream  or  to  the  number  of  graded 
branch  streams  to  be  taken  as  guides  for  the  imaginary  warped 
base-level,  so  no  limit  can  be  set  between  the  graded  stream 
courses  and  the  graded  waste  slopes  of  their  head  or  along  their 
sides.  The  imaginary  surface  should,  if  conceived  at  all,  follow 
the  lead  of  all  the  graded  lines  and  surfaces  as  fast  as  they  are 
developed  ;  it  should  be  extended  as  they  are  extended,  modified 
as  they  are  modified.  But  if  this  be  agreed  to,  part  of  the  imagi- 
nary surface  becomes  a  real  surface,  and  the  rest  may  be  neglected 
until  it  also  is  realized. 

Just  as  every  reach  in  a  stream  is  graded  with  respect  to  the 
next  downstream  barrier  or  local  base-level,  so  every  waste  slope 
is  graded  with  respect  to  the  ledge  or  cliff  at  its  lower  margin ; 
the  lowest  reach,  ending  at  the  river  mouth,  is  graded  with  refer- 
ence to  the  general  base-level  or  the  ocean  ;  the  lowest  graded 
slope  of  a  valley  side  is  graded  with  reference  to  the  stream  (or 
flood  plain)  in  the  valley  bottom.  Again,  every  bare  ledge  on 
a  mountain  side  will,  in  time,  be  graded  (or  consumed)  by  the 
head  ward  growth  of  the  graded  slope  next  below  it,  just  as  every 
ledge  of  rocks  that  makes  a  fall  or  rapid  at  the  head  of  a  reach 
will,  in  time,  be  obliterated  by  the  upstream  extension  of  the 
graded  reach.  (In  both  cases,  when  the  time  of  extinction  of 
the  ledge  is  attained,  the  waste  slope  and  the  stream  reach  will 
probably  have  been  worn  somewhat  farther  into  the  land  mass, 
assuming  a  somewhat  fainter  declivity  —  that  is,  coming  closer 
to  base-level  —  than  was  the  case  while  the  ledge  still  existed.) 

The  close  similarity,  the  real  homology  between  the  two  classes 
of  streams,  makes  it  all  the  clearer  that  "  base-level"  is  not  a  good 
term  to  apply  to  either.  It  is  not  desirable  to  say  that  a  hillside 
ledge  is  "base-leveled  "  when  it  is  worn  back  so  far  that  it  disap- 
pears under  the  slope  of  the  growing  sheet  of  waste ;  yet  it  is 


404  PHYSIOGRAPHIC  ESSAYS 

certainly  desirable  to  indicate  by  the  use  of  an  appropriate  termi- 
nology that  the  disappearance  of  the  ledge  has  been  accomplished 
by  changes  of  the  same  kind  as  those  which  have  caused  the  ob- 
literation of  falls  and  rapids  in  rivers.  Hence  it  seems  desirable 
to  say  that  every  ledge,  in  valley  side  or  stream  bed,  will  in  time 
be  graded  —  not  base-leveled  —  with  respect  to  the  attitude  as- 
sumed at  that  future  time  by  the  graded  —  not  base-leveled  — 
reach  or  slope  next  below  it. 

It  is,  perhaps,  on  account  of  the  elusive  character  of  the  imagi- 
nary warped  surface  that  its  definition  is  sometimes  couched  in 
indefinite  language.  In  the  original  definition,  Powell  said : 

I  take  some  liberty  in  using  the  term  "level"  in  this  connection,  as  the 
action  of  a  stream  in  wearing  its  channel  ceases,  for  all  practical  purposes, 
before  its  bed  has  quite  reached  the  level  of  the  lower  end  of  the  stream. 
What  I  have  called  the  base-level  would,  in  fact,  be  an  imaginary  surface, 
inclining  slightly  («,  204). 

In  a  later  paper  he  said  again  : 

It  will  be  understood  that  the  land  plain  which  is  brought  down  to  the  level 
of  the  sea  has  its  margin  on  the  seashore,  and  that  it  extends  back  from  the 
shore  a  distance  which  may  be  miles  or  hundreds  of  miles.  As  it  stretches 
back,  its  surface  rises  slightly.  The  whole  plain  is  not  brought  down  abso- 
lutely to  the  level  of  the  sea,  but  only  nearly  to  that  level  (<£,  34,  35). 

Salisbury  states  that  "  no  definite  degree  of  slope  can  be  fixed 
upon  as  marking  a  base-level."  Geikie  defines  base-level  as  "a 
level  not  much  above  that  of  the  sea."  Brigham  writes  : 

The  great  river  first  cuts  its  bed  close  to  the  sea-level,  and  we  say  that 
a  portion  of  the  valley  is  reduced  to  base-level.  It  lacks  a  little  of  it,  but 
the  difference  is  so  small  that  we  neglect  it. 

These  qualified  statements  are  apparently  the  result  of  attempt- 
ing to  define  a  surface  in  terms  of  its  variable  feature,  slope, 
instead  of  in  terms  of  its  constant  feature,  balance  of  activities. 
Whatever  slope  is  agreed  upon  must  change  to  a  fainter  slope  if 
more  time  is  allowed  ;  but  the  balance,  once  struck,  is  always 
maintained  as  long  as  the  cycle  endures.  Another  cause  of  diffi- 
culty in  definition  seems  to  have  arisen  from  giving  the  same 
name  to  a  variable  and  to  its  limit.  Both  the  imaginary  warped 
surface  and  the  actual  peneplain  are  essentially  variables ;  their 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  405 

variations  are  similar  and  systematic  ;  they  both  approach,  but 
never  reach,  the  limiting  base  of  sub-aerial  erosion.  The  latter  is 
essentially  a  constant,  accurately  definable  from  the  beginning, 
and  remaining  unchanged  while  the  variable  surfaces  approach 
it.  It  may  be  defined  as  the  limit  of  either  of  these  variables  in 
a  strictly  mathematical  fashion.  The  base-level  is  the  level  base 
toward  which  the  land  surface  constantly  approaches  in  accordance 
with  the  laws  of  degradation,  but  which  it  can  never  reach. 

Plains  and  Peneplains.  The  names  for  surfaces  of  ultimate 
and  penultimate  sub-aerial  erosion  deserve  brief  consideration. 
My  own  preference,  prejudiced,  perhaps,  by  a  share  that  I  have 
had  in  making  up  names,  would  be  to  avoid  "  base-level "  as  a 
technical  name  for  any  geographical  form,  to  use  "plain"  spar- 
ingly for  surfaces  of  erosion,  because  of  the  rare  occurrence  of 
complete  or  ultimate  planation  ;  and  usually  to  employ  "  pene- 
plain "  as  the  name  for  the  penultimate  form  developed  in  a  cycle 
of  erosion.  It  was  in  order  to  avoid  the  implication  of  complete 
erosion,  and  the  objections  that  such  an  implication  aroused,  that 
the  term  "peneplain"  was  suggested  thirteen  years  ago.  This 
word  gradually  came  into  use  with  quotation  marks  and  an  ex- 
planatory footnote.  The  footnote  disappeared  first,  and  now  the 
quotation  marks  are  frequently  omitted,  as  if  the  word  had  gained 
an  established  position,  although  among  writers  in  Great  Britain 
the  need  of  the  term  is  still  so  little  felt  that  it  is  generally  men- 
tioned as  an  American  invention  when  used  at  all,  instead  of 
being  fully  adopted,  like  "delta  "  and  "  atoll,"  without  explanation 
or  acknowledgment. 

There  seems  to  be  to-day  less  hesitation  regarding  the  accept- 
ance of  the  idea  of  far-advanced  sub-aerial  degradation  than  there 
was  fifteen  years  ago,  —  witness  the  use  of  "  plain  of  erosion"  by 
Hobbs  (137)  as  a  name  for  the  worn-down  surface,  now  uplifted 
and  dissected,  in  the  uplands  of  Connecticut ;  nevertheless  it  still 
seems  desirable  to  speak  of  such  surfaces  as  peneplains  in  the 
absence  of  proof  that  they  were  actually  reduced  to  plains.  The 
alternatives  for  peneplain  are  as  follows  : 

Powell  contrasts  "gradation  or  true  plains"  with  "diastrophic 
plains"  (plateaus),  the  former  being  produced  by  gradation,  a 
"process  accomplished  through  the  agency  of  water,"  and  the 


406  PHYSIOGRAPHIC  ESSAYS 

latter  by  the  uplifting  of  the  earth's  crust.  This  use  of  "  grada- 
tion "  is  a  natural  complement  of  the  use  of  "  grade  "  in  the  sense 
advocated  in  this  essay.  Gradation  plains  are  then  treated  under 
four  heads:  "sea  plains,"  "lake  plains,"  "stream  plains,"  and 
"flood  plains."  Of  the  first  class  it  is  said: 

Whenever  in  any  region  the  process  of  slow  upheaval  comes  to  an  end, 
and  such  district  is  still  subject  to  degradation  by  rains  and  streams,  the 
process  of  reduction  goes  on  until  the  surface  is  brought  down  to  the  level 
of  the  sea.  .  .  .  The  sea-level  plain  is  permanent  in  the  absence  of  dias- 
trophism.  .  .  .  Low  lands  with  surfaces  more  inclined,  and  with  more 
swiftly  running  streams,  are  still  called  "  plains,"  though  they  are  not  fully 
brought  down  to  base-level;  sometimes  they  are  called  "  peneplains" 
(A  34,  35). 

"  Sea  plain  "  has  not  come  into  general  use,  perhaps  because 
of  possible  confusion  with  "sea-cut  plains,"  "or  plains  of  marine 
denudation."  The  following  extract  gives  an  example  of  the 
employment  of  the  term  with  double  meaning  by  Hughes,  in 
describing  the  uplands  of  western  Yorkshire : 

It  is  to  both  of  the  agencies  above  mentioned  [marine  and  sub-aerial 
erosion],  acting  simultaneously  throughout  long  ages,  that  we  must  refer 
the  tremendous  results  that  we  have  forced  upon  our  attention.  .  .  .  We 
will  refer  to  these  great  plateaus  by  the  shorter  term  "  sea  plain,"  to  dis- 
tinguish them  from  the  river  plains  or  bed  plains  (131). 

Dryer  uses  the  phrase  "  graded  plain  "  in  a  somewhat  different 
sense.  The  reduction  of  the  border  of  a  land  area  to  a  submarine 
plain  by  sea  action,  while  the  rest  of  the  land  surface  is  reduced 
to  base-level  by  sub-aerial  processes,  would  result  in  the  pro- 
duction of  a  "  graded  plain,  lying  partly  above  and  partly  below 
sea-level"  (234).  No  example  of  this  kind  of  plain  is  mentioned. 
"Gradation  plain"  is  used  by  Adams  for  a  locally  developed 
peneplain  between  residual  ridges  (508). 

The  terminology  employed  by  Hayes  departs  somewhat  from 
that  in  use  with  other  writers.  He  says : 

The  processes  which  tend  to  produce  a  base-level  plain  are  embraced 
under  the  term  "gradation."  This  includes  aggradation  and  degradation.  .  .  . 
A  "  base-leveled  surface  "  is  any  land  surface,  however  small,  which  has  been 
brought  approximately  to  a  base-level,  either  general  or  local,  by  the  processes 
of  gradation.  When  such  a  surface  has  considerable  extent  it  becomes 
a  "base-level  plain."  .  .  .  The  term  "base-level  peneplain,"  or  simply 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  407 

"  peneplain,"  is  applied  to  a  surface  of  which  a  greater  or  less  proportion 
has  been  reduced  to  the  condition  of  a  base-level  plain,  but  which  con- 
tains also  some  unreduced  residual  areas  (21,  22). 

It  seems  to  me  that  it  is  going  too  far  to  say  that  "a  base-leveled 
surface  is  any  land  surface,  however  small,  which  has  been  brought 
approximately  to  a  base-level,  either  general  or  local."  It  would 
follow  from  this  definition  that,  inasmuch  as  every  point  in  a  con- 
tinuously graded  river  is  a  local  base-level  for  every  other  point 
farther  upstream,  the  upper  stretches  of  the  flood  plain  or  broad 
valley  floor  of  a  large  river  would  be  called  a  base-leveled  surface, 
in  spite  of  their  standing  several  hundreds,  or  even  thousands,  of 
feet  above  the  general  base-level.  The  valley  plain  of  the  Platte, 
for  example,  attains  altitudes  of  more  than  three  thousand  feet, 
and  cannot  be  fitly  described  as  a  base-level  plain,  unless  base- 
level  is  taken  to  mean  a  sloping  surface.  It  may  be  more  appro- 
priately called  a  graded  valley  plain,  or  a  graded  valley  floor,  for 
these  terms  do  not  contain  any  implication  that  the  surface  is 
either  low  or  level. 

Another  objection  to  the  above  use  of  "  base-leveled  surface" 
is  that  it  arbitrarily  separates  graded  valley  floors  and  graded  hill- 
sides, whose  analogies  with  respect  to  the  processes  of  gradation 
ought  to  be  exhibited  rather  than  concealed  in  a  systematic  ter- 
minology. It  can  hardly  be  supposed  that  any  one  would  to-day 
call  a  waste-covered  hillside  a  "base-leveled  surface,"  although  it 
has  every  characteristic  with  respect  to  the  processes  of  gradation 
that  is  possessed  by  a  graded  valley  floor.  A  third  objection  to 
this  use  of  "base-leveled  surface"  would  be  found  when  applying 
it  to  the  High  plains  of  eastern  Colorado  and  western  Kansas, 
which,  according  to  the  explanation  offered  by  Johnson  and  cited 
above,  were  produced  by  aggradation  during  a  time  of  less  rainfall 
than  at  present.  Here  an  extended  surface  was,  as  Hayes  might 
phrase  it,  "  brought  approximately  to  a  base-level,  either  general 
or  local,  by  the  processes  of  gradation,"  and  yet  it  was  actually 
built  up  hundreds  of  feet  above  the  preexistent  and  the  present 
valleys,  and  thousands  of  feet  above  the  general  base-level,  al- 
though there  is  no  indication  of  any  discontinuity  in  the  graded 
surface  between  the  High  plains  and  the  mouths  of  their 
aggrading  rivers.  The  High  plains  are  better  called  aggraded 


408  PHYSIOGRAPHIC  ESSAYS 

river-made  plains,  or  "fluviatile  plains";  and  in  this  respect  they 
resemble  the  great  plains  of  northern  India. 

The  Geographical  Cycle.  The  period  of  time  during  which  an 
uplifted  land  mass  undergoes  its  transformations  by  the  processes 
of  land  sculpture,  ending  in  a  low,  featureless  plain,  has  been 
called  a  geographical  cycle,  or,  as  Lawson  phrases  it,  a  "geo- 
morphic  cycle"  (253).  Hayes  writes:  "The  term  'gradation 
period '  is  employed '  for  the  entire  time  during  which  the  base- 
level  remains  in  one  position ;  that  is,  the  interval  between  two 
elevations  of  the  earth's  surface  of  sufficient  magnitude  to  pro- 
duce a  marked  change  in  the  position  of  sea-level "  (22);  but  on 
later  pages  he  uses  the  phrase  "cycles  of  gradation,"  or  simply 
"cycles,"  instead  of  "gradation  periods."  It  matters  little  which 
of  these  terms  is  used,  but  it  would  certainly  be  an  advantage 
that  only  one  should  be  retained  to  express  the  single  idea  here 
considered. 

Denudation  and  Degradation.  It  seems  worth  while  to  call 
attention  in  this  connection  to  the  desirability  of  a  more  careful 
discrimination  than  is  customary  between  the  terms  "denudation" 
and  "degradation."  "Denudation"  might  be  used  advisedly  as 
the  name  of  those  active  processes,  chiefly  operative  in  the  yo..th 
and  maturity  of  a  cycle,  by  which  rock  structures  are  laid  bare, 
literally  denuded,  because  their  waste  is  removed  as  fast  as  it  is 
formed.  "  Degradation,"  on  the  other  hand,  is  more  appropriately 
associated  with  those  leisurely  processes,  characteristic  of  the 
later  stages  of  the  cycle,  in  which  a  graded  slope  is  reduced  to 
fainter  and  fainter  declivity,  although  maintaining  its  graded  con- 
dition all  the  while.  Aggradation  is  naturally  the  opposite  of 
degradation,  and  implies  the  deposition  of  rock  waste  by  trans- 
porting agencies,  the  built-up  surface  being  always  kept  essen- 
tially at  grade.  Thus  defined,  denudation  would  accompany  the 
early  work  of  downward  corrasion  by  streams,  and  the  longer- 
lasting  work  of  valley  widening  by  weathering  and  washing.  It 
would  be  systematically  transmuted  into  degradation  as  the  proc- 
esses that  operate  on  the  various  lines  of  down-slope  streaming 
attained  the  graded  condition ;  the  large  rivers  first,  the  smaller 
branch  streams  later ;  the  headwater  streamlets  and  the  hillside 
waste  streams  later  still.  Retreating  cliffs  and  summit  ledges, 


BASE-LEVEL,  GRADE,  AND  PENEPLAIN  409 

the  last  strongholds  of  denudation,  would  pass  into  the  phase  of 
degradation  when  they  are  reduced  under  th*e  graded  waste  cover 
in  the  stage  of  subdued  relief,  characteristic  of  late  maturity  and 
early  old  age  ;  and  thenceforward  all. further  erosion  would  be  by. 
degradation  alone. 

Conclusion.  It  may  seem  at  first  reading  that  this  essay  is 
concerned  with  words  rather  than  with  facts ;  but  such  is  not  my 
intention.  My  object  has  been  primarily  to  secure  a  just  and 
accurate  recognition  of  facts,  and  only  secondarily  to  attach  words 
to  the  facts  as  convenient  handles  by  which  to  bring  the  facts 
forward.  It  is  a  fact  of  large  import  that  the  wearing  down  of 
land  masses  proceeds  in  an  orderly  manner,  involving  the  dis- 
closure of  bare  rock  ledges  (denudation)  in  the  earlier  stages  of 
the  cycle  of  erosion,  and  the  concealment  of  all  ledges  under  a. 
graded  sheet  of  waste  in  the  later  stages  of  the  cycle  (degra- 
dation). It  is  a  fact  of  much  delicacy  that  streams  tend  to  assume 
a  balanced  condition  as  to  corrasion  and  transportation  ;  that 
after  once  attaining  this  condition  they  preserve  it  as  long  as 
their  work  continues  without  disturbance ;  but  that  the  slope  of 
their  graded  courses  must  vary  systematically  through  the  stages 
of  maturity  and  old  age,  as  well  as  through  changes  of  climate. 
It  is  a  fact  of  great  value  in  geographical  description  that  the 
balanced  condition  of  water  streams  is  imitated  so  closely  by 
that  of  waste  streams  that  one  set  of  terms  applies  to  both 
kinds  of  streams. 

There  can  be  no  question  that  the  adoption  of  a  suitable  term 
as  the  name  for  a  fact  is  a  great  aid  to  the  general  recognition 
of  the  fact  itself.  It  is  largely  on  this  account,  as  well  as  in  the 
interests  of  a  precise  terminology,  that  I  have  here  written  out  a 
series  of  notes  that  have  been  gathered  during  the  past  two  years, 
and  of  which  some  account  was  given  at  the  meeting  of  the  Geo- 
logical Society  of  America  in  Washington,  in  December,  1899. 

It  is  admittedly  difficult  always  to  use  terms  in  a  manner  that 
is  perfectly  consistent  with  their  definitions.  It  is  rarely  possible 
to  limit  terms  to  a  single  meaning.  It  is  probable  that  in  this  at- 
tempt to  reduce  our  terminology  to  greater  simplicity  and  better 
order  than  now  prevails,  I  have  laid  myself  open  to  criticism  on 
ths  very  grounds  that  are  objected  to  in  the  course  of  this  essay. 


410  PHYSIOGRAPHIC  ESSAYS 

Further  discussion  may  therefore  be  advisedly  directed  to  a  settle- 
ment of  open  questions.  It  is  certainly  open  to  consideration 
whether  "denudation"  and  " degradation  "  should  be  limited  as 
above  suggested  ;  but  the  advisability  of  holding  "  base-level " 
and  "grade  "to  the  meanings  here  indicated  seems  to  be  much 
less  open  to  difference  of  opinion.  The  future  meanings  of  these 
words  will  depend  much  lesst  on  the  preference  of  the  older 
geologists  and  geographers  of  to-day  than  on  that  of  their  younger 
successors.  I  therefore  urge  those  who  are  now  taking  up  the 
use  of  such  terms  as  "base-level"  and  "grade,"  "denudation" 
and  "degradation,"  to  consider  carefully  the  meaning  to  be 
adopted  for  them. 

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Philippson,  A.    "Ein  Beitrag  zur  Erosionstheorie."    Petermanns  Mittheil- 

ungen,  XXXII  (1886),  67-79. 
Powell,  J.  W.    (a)  Exploration  of  the  Colorado  River  of  the  West  and  its 

Tributaries.     Washington,  1875. 

(b)  "Physiographic  Processes";   "Physiographic  Features."    Nat.  Geog. 
Mon.  (1895),  1-32,  33-64.     New  York,  American  Book  Co. 


412  PHYSIOGRAPHIC  ESSAYS 

Rice,  W.  N.,  editor  of  Revised  Text-Book  of  Geology,  by  James  D.  Dana. 

New  York,  American  Book  Co.,  1897. 

Russell,  I.  C.     Rivers  of  North  America.    New  York,  Putnam,  1898. 
Salisbury,  R.  D.     (a)  "Surface  Geology."    GeoL  Surv.  New  Jersey,  Ann. 

Rep.  State  GeoL  for  1892-1893,  35-246. 
(£)  "  The  Physical  Geography  of  New  Jersey."    Geol.  Surv.  New  Jersey, 

Final  Report,  IV  (1898). 

Scott,  W.  B.  An  Introduction  to  Geology.  New  York,  Macmillan,  1897. 
Tarr,  R.  S.  Elementary  Physical  Geography.  New  York,  Macmillan,  1895. 
Van  Hise,  C.  R.  "A  Central  Wisconsin  Base-Level."  Science,  IV  (1896), 

57-59- 
Willis,  B.     (a)  "The  Northern  Appalachians."     Nat.  Geog.  Mon.  (1895), 

169-202.     New  York,  American  Book  Co. 

(^)  "Paleozoic  Appalachia."    Geol.  Surv.  Maryland,  IV  (1900),  23-93. 
Winslow,  A.    "Lead  and  Zinc  Deposits."  Geol.  Surv.  Missouri,  VI  (1894). 


XIX 

THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA 

In  Faltensystemen  von  sehr  hohem  Alter  wurde  die  urspriingliche 
Anordnung  der  Langenthaler  durch  das  Ueberhandnehmen  der  transversalen 
Erosionsfurchen  oft  ganz  und  gar  verwischt.  —  Lowl,  Petermanns  Mittheil- 
ungen,  XXVIII  (1882),  411. 

I.  INTRODUCTORY 

Plan  of  Work  here  Proposed.  No  one  now  regards  a  river 
and  its  valley  as  ready-made  features  of  the  earth's  surface.  All 
are  convinced  that  rivers  have  come  to  be  what  they  are  by  slow 
processes  of  natural  development,  in  which  every  peculiarity  of 
river  course  and  valley  form  has  its  appropriate  cause.  Being  fully 
persuaded  of  the  gradual  and  systematic  evolution  of  topographical 
forms,  it  is  now  desired,  in  studying  the  rivers  and  valleys  of 
Pennsylvania,  to  seek  the  causes  of  the  location  of  the  streams  in 
their  present  courses  ;  to  go  back,  if  possible,  to  the  early  date 
when  central  Pennsylvania  was  first  raised  above  the  sea,  and 
trace  the  development  of  the  several  river  systems  then  implanted 
upon  it  from  their  ancient  beginning  to  the  present  time. 

The  existing  topography  and  drainage  system  of  the  state  will 
first  be  briefly  described.  We  must  next  inquire  into  the  geolog- 
ical structure  of  the  region,  follow  at  least  in  a  general  way  the 
deformations  and  changes  of  attitude  and  altitude  that  it  has  suf- 
fered, and  consider  the  amount  of  denudation  that  has  been 
accomplished  on  its  surface.  We  must  at  the  same  time  bear  in 
mind  the  natural  history  of  rivers,  their  morphology  and  develop- 
ment ;  we  must  recognize  the  varying  activities  of  a  river  in  its 
youth  and  old  age,  the  adjustments  of  its  adolescence  and  maturity, 
and  the  revival  of  its  decrepit  powers  when  the  land  that  it  drains 
is  elevated  and  it  enters  a  new  cycle  of  life.  Finally,  we  shall 
attempt  to  follow  out  the  development  of  the  rivers  of  Pennsyl- 
vania by  applying  the  general  principles  of  river  history  to  the 
special  case  of  Pennsylvania  structure. 

413 


PHYSIOGRAPHIC  ESSAYS 

General  Description  of  the  Topography  of  Pennsylvania.  The 
strongly  marked  topographical  districts  of  Pennsylvania  can 
hardly  be  better  described  than  by  quoting  the  account  given 
over  a  century  ago  by  Lewis  Evans,  of  Philadelphia,  in  his 
"Analysis  of  a  Map  of  the  Middle  British  Colonies  in  America" 
(I755)>  which  is  as  valuable  from  its  appreciative  perception  as 
it  is  interesting  from  its  early  date.  The  following  paragraphs 
are  selected  from  his  early  pages  : 

The  land  southwestward  of  Hudson's  River  is  more  regularly  divided  and 
into  a  greater  number  of  stages  than  the  other.  The  first  object  worthy  of 
regard  in  this  part  is  a  rief  or  vein  of  rocks  of  the  talky  or  isinglassy  kind, 
some  two  or  three  or  half  a  dozen  miles  broad  ;  rising  generally  some  small 
matter  higher  than  the  adjoining  land  ;  and  extending  from  New  York  city 
southwesterly  by  the  lower  falls  of  Delaware,  Schuylkill,  Susquehanna, 
Gun-Powder,  Patapsco,  Potomack,  Rapahannock,  James  River,  and  Ronoak. 
This  was  the  antient  maritime  boundary  of  America  and  forms  a  very  reg- 
ular curve.  The  land  between  this  rief  and  the  sea  and  from  the  Navesink 
hills  southwest  .  .  .  may  be  denominated  the  Lower  Plains,  and  consists  of 
soil  washt  down  from  above  and  sand  accumulated  from  the  ocean.  Where 
these  plains  are  not  penetrated  by  rivers,  they  are  a  white  sea-sand,  about 
twenty  feet  deep  and  perfectly  barren,  as  no  mixture  of  soil  helps  to  enrich 
them.  But  the  borders  of  the  rivers,  which  descend  from  the  uplands,  are 
rendered  fertile  by  the  soil  washt  down  with  the  floods  and  mixt  with  the 
sands  gathered  from  the  sea.  The  substratum  of  sea-mud,  shells  and  other 
foreign  subjects  is  a  perfect  confirmation  of  this  supposition.  And  hence  it 
is  that  for  forty  or  fifty  miles  inland  and  all  the  way  from  the  Navesinks  to 
Cape  Florida,  all  is  .a  perfect  barren  where  the  wash  from  the  uplands  has 
not  enriched  the  borders  of  the  rivers ;  or  some  ponds  and  defiles  have  not 
furnished  proper  support  for  the  growth  of  white  cedars.  ... 

From  this  rief  of  rocks,  over  which  all  the  rivers  fall,  to  that  chain  of 
broken  hills,  called  the  South  mountain,  there  is  the  distance  of  fifty,  sixty, 
or  seventy  miles  of  very  uneven  ground,  rising  sensibly  as  you  advance  fur- 
ther inland,  and  may  be  denominated  the  Upland.  This  consists  of  veins  of 
different  kinds  of  soil  and  substrata  some  scores  of  miles  in  length ;  and  in 
some  places  overlaid  with  little  ridges  and  chains  of  hills.  The  declivity  of 
the  whole  gives  great  rapidity  to  the  streams ;  and  our  violent  gusts  of  rain 
have  washt  it  all  into  gullies,  and  carried  down  the  soil  to  enrich  the  borders 
of  the  rivers  in  the  Lower  Plains.  These  inequalities  .render  half  the  country 
not  easily  capable  of  culture,  and  impoverishes  it,  where  torn  up  by  the 
plow,  by  daily  washing  away  the  richer  mould  that  covers  the  surface. 

The  South  mountain  is  not  in  ridges  like  the  Endless  mountains,  but  in 
small,  broken,  steep,  stoney  hills ;  nor  does  it  run  with  so  much  regularity. 
In  some  places  it  gradually  degenerates  to  nothing,  not  to  appear  again  for 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    415 

some  miles,  and  in  others  it  spreads  several  miles  in  breadth.  Between 
South  mountain  and  the  hither  chain  of  the  Endless  mountains  (often  for 
distinction  called  the  North  mountain,  and  in  some  places  the  Kittatinni 
and  Pequelin),  there  is  a  valley  of  pretty  even  good  land,  some  eight,  ten, 
or  twenty  miles  wide,  and  is  the  most  considerable  quantity  of  valuable  land 
that  the  English  are  possest  of ;  and  runs  through  New  Jersey,  Pensilvania, 
Mariland  and  Virginia.  It  has  yet  obtained  no  general  name,  but  may 
properly  enough  be  called  Piemont,  from  its  situation.  Besides  conveniences 
always  attending  good  land,  this  valley  is  everywhere  enriched  with 
Limestone. 

The  Endless  mountains,  so  called  from  a  translation  of  the  Indian  name 
bearing  that  signification,  come  next  in  order.  They  are  not  confusedly 
scattered  -and  in  lofty  peaks  overtopping  one  another,  but  stretch  in  long 
uniform  ridges  scarce  half  a  mile  perpendicular  in  any  place  above  the  inter- 
mediate vallies.  Their  name  is  expressive  of  their  extent,  though  no  doubt 
not  in  a  literal  sense.  .  .  .  The  mountains  are  almost  all  so  many  ridges  with 
even  tops  and  nearly  of  a  height.  To  look  from  these  hills  into  the  lower 
lands  is  but,  as  it  were,  into  an  ocean  of  woods,  swelled  and  deprest  here 
and  there  by  little  inequalities,  not  to  be  distinguished  one  part  from  another 
any  more  than  the  waves  of  the  real  ocean.  The  uniformity  of  these  moun- 
tains, though  debarring  us  of  an  advantage  in  this  respect,  makes  some 
amends  in  another.  They  are  very  regular  in  their  courses,  and  confine  the 
creeks  and  rivers  that  run  between ;  and  if  we  know  where  the  gaps  are 
that  let  through  these  streams,  we  are  not  at  a  loss  to  lay  down  their  most 
considerable  inflections.  .  .  . 

To  the  northwestward  of  the  Endless  mountains  is  a  country  of  vast 
extent,  and  in  a  manner  as  high  as  the  mountains  themselves.  To  look  at 
the  abrupt  termination  of  it,  near  the  sea  level,  as  is  the  case  on  the  west 
side  of  Hudson's  River  below  Albany,  it  looks. as  a  vast  high  mountain; 
for  the  Kaats  Kills,  though  of  more  lofty  stature  than  any  other  mountains  in 
these  parts  of  America,  are  but  the  continuation  of  the  Plains  on  the  top, 
and  the  cliffs  of  them  in  the  front  they  present  towards  Kinderhook.  These 
Upper  Plains  are  of  extraordinary  rich  level  land,  and  extend  from  the 
Mohocks  River  through  the  country  of  the  Confederates.1  Their  termination 
northward  is  at  a  little  distance  from  Lake  Ontario ;  but  what  is  westward 
is  not  known,  for  those  most  extensive  plains  of  Ohio  are  part  of  them. 

These  several  districts  recognized  by  Evans  may  be  summarized 
as  the  coastal  plain  of  nearly  horizontal  Cretaceous  and  later  beds, 
just  entering  the  southeastern  corner  of  Pennsylvania  ;  the  mar- 
ginal upland  of  contorted  schists  of  disputed  age  ;  the  South 
mountain  belt  of  ancient  and  much  disturbed  crystalline  rocks, 
commonly  called  Archaean  ;  a  space  between  these  two  traversed 

1  Referring  to  the  league  of  Indian  tribes,  so  called. 


416  PHYSIOGRAPHIC  ESSAYS 

by  the  sandstone  lowland  of  the  Newark  formation1 ;  the  great 
Appalachian  valley  of  crowded  Cambrian  limestones  and  slates  ; 
the  region  of  the  even-crested,  linear,  Paleozoic  ridges,  bounded  by 
Kittatinny,  or  Blue  mountain,  on  the  southeast  and  by  Allegheny 
mountain  on  the  northwest,  this  being  the  area  with  which  we 
are  here  most  concerned  ;  and  finally  the  Allegheny  plateau, 
consisting  of  nearly  horizontal  Devonian  and  Carboniferous  beds, 
and  embracing  all  the  western  part  of  the  state.  The  whole 
region  presents  the  most  emphatic  expression  not  only  of  its 
structure,  but  also  of  the  more  recent  cycles  of  development 
through  which  it  has  passed. 

The  Drainage  of  Pennsylvania.  The  greater  part  of  the  Alle- 
gheny plateau  is  drained  westward  into  the  Ohio,  and  with  this 
we  shall  have  little  to  do.  The  remainder  of  the  plateau  drainage 
reaches  the  Atlantic  by  two  rivers,  the  Delaware  and  the  Susque- 
hanna,  of  which  the  latter  is  the  more  special  object  of  our  study. 
The  North  and  West  branches  of  the  Susquehanna  rise  in  the 
plateau,  which  they  traverse  in  deep  valleys  ;  thence  they  enter 
the  district  of  the  central  ranges,  where  they  unite  and  flow  in 
broad  lowlands  among  the  even-crested  ridges.  The  Juniata 
brings  the  drainage  of  the  Broad  Top  region  to  the  main  stream 
just  before  their  confluent  current  cuts  across  the  marginal  Blue 
mountain.  The  rock-rimmed  basins  of  the  anthracite  region  are 
drained  by  small  branches  of  the  Susquehanna  northward  and 
westward,  and  by  the  Schuylkill  and  Lehigh  to  the  south  and 
east.  The  Delaware,  which  traverses  the  plateau  between  the 
anthracite  region  and  the  Catskill  mountain  front,  together  with 
the  Lehigh,  the  Schuylkill,  the  little  Swatara,  and  the  Susque- 
hanna, cut  the  Blue  mountain  by  fine  water  gaps,  and  cross  the 
great  limestone  valley.  The  Lehigh  then  turns  eastward  and  joins 
the  Delaware,  and  the  Swatara  turns  westward  to  the  Susque- 
hanna ;  but  the  Delaware,  Schuylkill,  and  Susquehanna  all  con- 
tinue across  South  mountain  and  the  Newark  belt,  and  into  the 
low  plateau  of  schists  beyond.  The  Schuylkill  unites  with  the 
Delaware  near  Philadelphia,  just  below  the  inner  margin  of 

1  Russell  has  recommended  the  revival  of  this  term,  proposed  many  years  ago 
by  Redfield,  as  a  non-committal  name  for  the  "  new  red  sandstones"  of  our 
Atlantic  slope,  commonly  called  Triassic. 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    417 

the  coastal  plain ;  the  Delaware  and  the  Susquehanna  continue 
in  their  deflected  estuaries  to  the  sea.  All  of  these  rivers  and 
many  of  their  side  streams  are  at  present  sunk  in  small  valleys 
of  moderate  depth  and  width,  below  the  general  surface  of  the 
lowlands,  and  are  more  or  less  complicated  with  terrace  gravels. 

Previous  Studies  of  Appalachian  Drainage.  There  have  been 
no  special  studies  of  the  history  of  the  rivers  of  Pennsylvania  in 
the  light  of  what  is  now  known  of  river  development.  A  few 
recent  essays  of  rather  general  character  as  far  as  our  rivers  are 
concerned,  may  be  mentioned. 

Peschel  examined  our  rivers  chiefly  by  means  of  general  maps, 
with  little  regard  to  the  structure  and  complicated  history  of  the 
region.  He  concluded  that  the  several  transverse  rivers  which 
break  through  the  mountains,  namely  the  Delaware,  Susquehanna, 
and  Potomac,  are  guided  by  fractures  anterior  to  the  origin  of 
the  rivers  (442).  There  does  not  seem  to  be  sufficient  evidence  to 
support  this  obsolescent  view,  for  most  of  the  water  gaps  are 
located  independently  of  fractures  ;  nor  can  Peschel's  method  of 
river  study  be  trusted  as  leading  to  safe  conclusions. 

Tietze  regards  our  transverse  valleys  as  antecedent  (600);  but 
this  was  only  a  general  suggestion,  for  his  examination  of  the 
structure  and  development  of  the  region  is  too  brief  to  establish 
this  and  exclude  other  views. 

Lowl  questions  the  conclusion  reached  by  Tietze,  and  ascribes 
the  transverse  gaps  to  the  backward  or  headwater  erosion  of 
external  streams,  a  process  which  he  has  done  much  to  bring 
into  its  present  important  position,  and  which  for  him  replaces 
the  persistence  of  antecedent  streams  of  other  authors  (a,  405  ;  b). 

A  brief  article  that  I  wrote  in  comment  on  Lowl's  first  essay 
several  years  ago  now  seems  to  me  insufficient  in  its  method  (a). 
It  exaggerated  the  importance  of  antecedent  streams ;  it  took 
no  sufficient  account  of  the  several  cycles  of  erosion  through 
which  the  region  has  certainly  passed  ;  and  it  neglected  due  con- 
sideration of  the  readjustment  of  initial  immature  stream  courses 
during  more  advanced  river  life.  Since  then,  a  few  words  in 
Lowl's  essay  have  come  to  have  more  and  more  significance  to 
me ;  he  says  that  in  mountain  systems  of  very  great  age  the 
original  arrangement  of  the  longitudinal  valleys  often  becomes 


418  PHYSIOGRAPHIC  ESSAYS 

entirely  confused  by  means  of  their  conquest  by  transverse  erosion 
gaps.  This  suggestion  has  been  so  profitable  to  me  that  I  have 
placed  the  original  sentence  at  the  beginning  of  this  paper.  Its 
thesis  is  the  essential  element  of  my  present  study. 

Philippson  refers  to  the  above-mentioned  authors  and  gives  a 
brief  account  of  the  arrangement  of  drainage  areas  within  our 
Appalachians,  but  briefly  dismisses  the  subject  (149).  His  essay 
contains  a  serviceable  bibliography. 

If  these  several  earlier  essays  have  not  reached  any  precise 
conclusion,  it  may  perhaps  be  because  the  details  of  the  geolog- 
ical structure  and  development  of  Pennsylvania  have  not  been 
sufficiently  examined.  Indeed,  unless  the  reader  has  already 
become  familiar  with  the  geological  maps  and  reports  of  the 
Pennsylvania  surveys,  and  is  somewhat  acquainted  with  its  geog- 
raphy, I  shall  hardly  hope  to  make  my  case  clear  to  him.  The 
volumes  that  should  be  most  carefully  studied  are,  first,  the 
always  inspiring  classic,  "Coal  and  its  Topography"  (1856),  by 
Lesley,  in  which  the  immediate  relation  of  our  topography  to 
the  underlying  structure  is  so  finely  described  ;  the  Geological 
Map  of  Pennsylvania  (1856),  the  result  of  the  labors  of  the  first 
survey  of  the  state ;  and  the  Geological  Atlas  of  Counties,  Vol- 
ume X  of  the  second  survey  (1885).  Besides  these,  the  ponderous 
volumes  of  the  final  report  of  the  first  survey  and  numerous 
reports  on  separate  counties  by  the  second  survey  should  be 
examined,  as  they  contain  many  accounts  of  the  topography, 
although  saying  very  little  about  its  development.  If,  in  addition 
to  all  this,  the  reader  has  seen  the  central  district  of  the  state 
and  marveled  at  its  even-crested,  straight,  and  zigzag  ridges,  and 
walked  through  its  narrow  water  gaps  into  the  inclosed  coves 
that  they  drain,  he  may  then  still  better  follow  the  considera- 
tions here  presented. 

II.    OUTLINE  OF  THE  GEOLOGICAL  HISTORY  OF  THE  REGION 

Conditions  of  Formation.  The  region  in  which  the  Susque- 
hanna  and  the  neighboring  rivers  are  now  located  is  built  in 
chief  part  of  marine  sediments  derived  in  Paleozoic  time  from  a 
large  land  area  to  the  southeast,  whose  northwest  coast  line 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    419 

probably  crossed  Pennsylvania  somewhere  in  the  southeastern 
part  of  the  state,  doubtless  varying  its  position,  however,  by 
many  miles  as  the  sea  advanced  and  receded  in  accordance  with 
the  changes  in  the  relative  altitudes  of  the  land  and  water  sur- 
faces, such  as  have  been  discussed  by  Newberry  and  Claypole. 
The  sediments  thus  accumulated  are  of  enormous  thickness, 
measuring  twenty  or  thirty  thousand  feet  from  their  crystalline 
foundation  to  the  uppermost  layer  now  remaining.  The  whole 
mass  is  essentially  conformable  in  the  central  part  of  the  state. 
Some  of  the  formations  are  resistant,  and  these  have  determined 
the  position  of  our  ridges ;  others  are  weaker,  and  are  chosen  as 
the  sites  of  valleys  and  lowlands.  The  first  are  the  Oneida  and 
Medina  sandstones,  —  which  will  be  here  generally  referred  to 
under  the  latter  name  alone,  —  the  Pocono  sandstone,  and  the 
Pottsville  conglomerate  ;  to  these  may  be  added  the  fundamental 
crystalline  mass  on  which  the  whole  series  of  bedded  formations 
was  deposited,  and  the  basal  sandstone  that  is  generally  asso- 
ciated with  it.  Wherever  we  now  see  these  harder  rocks,  they 
rise  above  the  surrounding  lowland  surface.  On  the  other  hand, 
the  weaker  beds  are  the  Cambrian  limestones  (Trenton)  and 
slates  (Hudson  river),  all  the  Silurian  except  the  Medina  above 
named,  the  whole  of  the  Devonian,  —  in  which,  however,  there 
are  two  hard  beds  of  subordinate  value,  the  Oriskany  sandstone 
and  a  Chemung  sandstone  and  conglomerate,  that  form  low  and 
broken  ridges  over  the  softer  ground  on  either  side  of  them,  — 
and  the  Carboniferous  (Mauch  Chunk)  red  shales  and  some  of 
the  weaker  sandstones  (Coal  Measures). 

Former  Extension  of  Strata  to  the  Southeast.  We  are  not 
much  concerned  with  the  conditions  under  which  this  great 
series  of  beds  was  formed ;  but,  as  will  appear  later,  it  is  impor- 
tant for  us  to  recognize  that  the  present  southeastern  margin  of 
the  beds  is  not  by  any  means  their  original  margin  in  that  direc- 
tion. It  is  probable  that  the  whole  mass  of  deposits,  with 
greater  or  less  variations  of  thickness,  extended  at  least  twenty 
miles  southeast  of  Blue  mountain,  and  that  many  of  the  beds 
extended  much  farther.  The  reason  for  this  conclusion  is  a 
simple  one.  The  several  resistant  beds  above  mentioned  consist 
of  quartz  sand  and  pebbles  that  cannot  be  derived  from  the 


420  PHYSIOGRAPHIC   ESSAYS 

underlying  beds  of  limestones  and  shales  ;  their  only  known 
source  lay  in  the  crystalline  rocks  of  the  Paleozoic  land  to  the 
southeast.  South  mountain  may  possibly  have  made  part  of  this 
Paleozoic  land  ;  but  it  seems  more  probable  that  it  was  land  only 
during  the  earlier  Archaean  age,  and  that  it  was  submerged  and 
buried  in  Cambrian  time  and  not  again  brought  to  the  light  of 
day  until  it  had  been  crushed  into  many  local  anticlines  (Lesley), 
whose  crests  were  uncovered  by  Permian  and  later  erosion.  The 
occurrence  of  Cambrian  limestone  on  either  side  of  South  moun- 
tain, taken  with  its  compound  anticlinal  structure,  makes  it  likely 
that  Medina  time  found  this  crystalline  area  entirely  covered  by 
the  Cambrian  beds  ;  Medina  sands  must  therefore  have  come 
from  still  farther  to  the  southeast.  A  similar  argument  applies 
to  the  source  of  the  Pocono  and  Pottsville  beds.  The  measure 
of  twenty  miles  as  the  former  southeastern  extension  of  the 
Paleozoic  formations  therefore  seems  to  be  a  moderate  one  for 
the  average  of  the  whole  series  ;  perhaps  forty  would  be  nearer 
the  truth. 

Cambro- Silurian  and  Permian  Deformations.  This  great 
series  of  once  horizontal  beds  is  now  wonderfully  distorted ; 
but  the  distortions  follow  a  general  rule  of  trending  northeast 
and  southwest,  and  of  diminishing  in  intensity  from  southeast  to 
northwest.  It  is  well'  known  that  in  the  Hudson  valley  a  con- 
siderable disturbance  occurred  between  Cambrian  and  Silurian 
time,  for  there  the  Medina  lies  unconformably  on  the  Hudson 
river  shales.  It  seems  likely,  for  reasons  that  will  be  briefly 
given  later  on,  that  the  same  disturbance  extended  into  Pennsyl- 
vania and  farther  southwest,  but  that  it  affected  only  the  south- 
eastern corner  of  the  state ;  and  that  the  unconformities  in 
evidence  of  it,  which  are  preserved  in  the  Hudson  valley,  are  here 
lost  by  subsequent  erosion.  Waste  of  the  ancient  land  and  its 
Cambro-Silurian  annex  still  continued  and  furnished  vast  beds  of 
sandstone  and  sandy  shales  to  the  remaining  marine  area,  until 
at  last  the  subsiding  Paleozoic  basin  was  filled  up  and  the  coal 
marshes  extended  broadly  across  it.  At  this  time  we  may  picture 
the  drainage  of  the  southeastern  land  area  wandering  rather 
slowly  across  the  great  Carboniferous  plains  to  the  still  sub- 
merged basin  far  to  the  west :  a  condition  of  things  that  is  not 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    421 

imperfectly  represented,  although  in  a  somewhat  more  advanced 
stage,  by  the  existing  drainage  of  the  mountains  of  the  Carolinas 
across  the  more  modern  coastal  plain  to  the  Atlantic. 

This  condition  was  interrupted  by  the  great  Permian  deforma- 
tion that  gave  rise  to  the  main,  ranges  of  the  Appalachians  in 
Pennsylvania,  Virginia,  and  Tennessee.  The  Permian  name  seems 
appropriate  here,  for  while  the  deformation  may  have  begun  at 
an  earlier  date,  and  may  have  continued  into  Triassic  time,  its 
culmination  seems  to  have  been  within  Permian  limits.  It  was 
characterized  by  a  resistless  force  of  compression,  exerted  in  a 
southeast-northwest  line,  in  obedience  to  which  the  whole  series 
of  Paleozoic  beds,  even  twenty  or  more  thousand  feet  in  thick- 
ness, was  crowded  gradually  into  great  and  small  folds,  trending 
northeast  and  southwest.  The  subjacent  Archaean  terrane  doubt- 
less shared  more  or  less  in  the  disturbance ;  for  example,  South 
mountain  is  described  by  Lesley  as  "  not  one  mountain,  but  a 
system  of  mountains  separated  by  valleys.  It  is,  geologically 
considered,  a  system  of  anticlinals  with  troughs  between.  .  .  . 
It  appears  that  the  South  mountain  range  ends  eastward  [in 
Cumberland  and  York  counties]  in  a  hand  with  five  [anti- 
clinal] fingers"  (6). 

It  may  be  concluded  with  fair  probability  that  the  folds  began 
to  rise  in  the  southeast,  where  they  are  crowded  closest  together, 
some  of  them  having  begun  here  while  coal  marshes  were  still 
forming  farther  west ;  and  that  the  last  folds  to  be  begun  were 
the  fainter  ones  on  the  plateau,  now  seen  in  Negro  mountain  and 
Chestnut  and  Laurel  ridges.  In  consequence  of  the  inequalities 
in  the  force  of  compression  or  in  the  resistance  of  the  yielding 
mass,  the  folds  do  not  continue  indefinitely  with  horizontal  axes, 
but  vary  in  height,  rising  or  falling  away  in  great  variety. 
Several  adjacent  folds  often  follow  some  general  control  in 
this  respect,  their  axes  rising  and  falling  together.  It  is  to  an 
unequal  yielding  of  this  kind  that  we  owe  the  location  of  the 
anthracite  synclinal  basins  in  eastern  Pennsylvania,  the  Coal  Meas- 
ures being  now  worn  away  from  the  prolongation  of  the  synclines, 
which  rise  in  either  direction. 

Perm-Triassic  Denudation.  During  and  for  a  long  time  after 
this  period  of  mountain  growth  the  destructive  processes  of 


422  PHYSIOGRAPHIC  ESSAYS 

erosion  wasted  the  land  and  lowered  its  surface.  An  enormous 
amount  of  material  was  thus  swept  away  and  laid  down  in  some 
unknown  ocean  bed.  We  shall  speak  of  this  as  the  Perm-Triassic 
period  of  erosion.  A  measure  of  its  vast  accomplishment  is  seen 
when  we  find  that  the  Newark  formation,  which  is  generally 
correlated  with  Triassic  or  Jurassic  time,  lies  unconformably  on 
the  eroded  surface  of  Cambrian  and  Archaean  rocks  in  the  south- 
eastern part  of  the  state,  where  we  have  concluded  that  the 
Paleozoic  series  once  existed ;  where  the  strata  must  have  risen 
in  a  great  mountain  mass  as  a  result  of  the  Appalachian  defor- 
mations ;  and  whence  they  must  therefore  have  been  denuded 
before  the  deposition  of  the  Newark  beds.  Not  only  so ;  the 
moderate  sinuosity  of  the  southeastern  or  under  boundary  of  the 
Newark  formation  indicates  clearly  enough  that  the  surface  on 
which  that  portion  of  the  formation  lies  is  one  of  no  great  relief 
or  inequality  ;  and  such  a  surface  -can  be  carved  out  of  an  ele- 
vated land  only  after  long-continued  denudation,  by  which  topo- 
graphical development  is  carried  beyond  the  time  of  its  greatest 
strength  or  maturity  into  the  fainter  expression  of  old  age. 
This  is  a  matter  of  some  importance  in  our  study  of  the  develop- 
ment of  the  rivers  of  Pennsylvania ;  and  it  also  constitutes  a 
good  part  of  the  evidence  already  referred  to  as  indicating  that 
there  must  have  been  some  earlier  deformations  of  importance 
in  the  southeastern  part  of  the  state ;  for  it  is  hardly  con- 
ceivable that  the  great  Paleozoic  mass  could  have  been  so  deeply 
worn  off  of  the  Newark  belt  between  the  making  of  the  last  of 
the  coal  beds  and  the  first  of  the  Newark.  It  seems  more  in 
accordance  with  the  facts  here  recounted  and  with  the  teachings 
of  geological  history  in  general  to  suppose,  as  we  have  here,  that 
something  of  the  present  deformation  of  the  ancient  rocks 
underlying  the  Newark  beds  was  given  at  an  early  date,  such 
as  that  of  the  Green  mountain  growth ;  and  that  a  certain 
amount  of  the  erosion  of  the  folded  beds  was  thus  made  possible 
in  middle  Paleozoic  time ;  then  again  at  some  later  date,  as 
Permian,  a  second  period  of  mountain  growth  arrived,  and 
further  folding  was  effected,  and  after  this  came  deeper  erosion, 
thus  dividing  the  destructive  work  that  was  done  into  several 
parts,  instead  of  crowding  it  all  into  the  post-Carboniferous 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    423 

time  ordinarily  assigned  to  it.  It  is  indeed  not  impossible  that 
an  important  share  of  what  we  have  called  the  Permian  defor- 
mation was,  as  above  suggested,  accomplished  in  the  southeastern 
part  of  the  state  while  the  coal  beds  were  yet  forming  in  the 
west ;  many  grains  of  sand  in  the  sandstones  of  the  Coal  Meas- 
ures may  have  had  several  temporary  halts  in  other  sandstone 
beds  between  the  time  of  their  first  erosion  from  the  Archaean 
rocks  and  the  much  later  time  when  they  found  the  resting 
place  that  they  now  occupy. 

Newark  Deposition.  After  the  great  Paleozoic  and  Perm- 
Triassic  erosions  thus  indicated,  when  the  southeastern  area  of 
ancient  mountains  had  been  well  worn  down  and  the  Permian 
folds  of  the  central  districts  had  acquired  a  well-developed 
drainage,  there  appeared  an  opportunity  for  local  deposition  in 
the  slow  depression  of  a  northeast-southwest  belt  of  the  deeply 
wasted  land,  across  the  southeastern  part  of  the  state ;  and  into 
this  trough-like  depression  the  waste  from  the  adjacent  areas  on 
either  side  was  carried,  building  the  Newark  formation.  This 
may  be  referred  to  as  the  Newark  or  Trias-Jurassic  period  of 
deposition.  The  volume  of  this  formation  is  unknown,  as  its 
thickness  and  original  area  are  still  undetermined ;  but  it  is 
pretty  surely  of  many  thousand  feet  in  vertical  measure,  and  its 
original  area  may  have  been  easily  a  fifth  or  a  quarter  in  excess 
of  its  present  area,  if  not  more  than  that.  So  great  a  local  accu- 
mulation seems  to  indicate  that  while  the  belt  of  deposition 
was  sinking,  the  adjacent  areas  were  rising,  in  order  to  furnish  a 
continual  supply  of  material ;  the  occurrence  of  heavy  conglom- 
erates along  the  margins  of  the  Newark  formation  confirms 
this  supposition,  and  the  heavy  breccias  near  Reading  indicate 
the  occurrence  of  a  strong  topography  and  a  strong  transporting 
agent  to  the  northwest  of  this  part  of  the  Newark  belt.  It  will 
be  necessary,  when  the  development  of  the  ancestors  of  our 
present  rivers  is  taken  up,  to  consider  the  effects  of  the  depres- 
sion that  determined  the  locus  of  Newark  deposition  and  of  the 
adjacent  elevation  that  maintained  a  supply  of  material. 

Jurassic  Tilting.  Newark  deposition  was  stopped  by  a  gradual 
reversal  of  the  conditions  that  introduced  it.  The  depression 
of  the  Newark  belt  was  after  a  time  reversed  into  elevation, 


424 


PHYSIOGRAPHIC  ESSAYS 


accompanied  by  a  peculiar  tilting,  and  again  the  waste  of  the 
region  was  carried  away  to  some  unknown  resting  place.  This 
disturbance,  which  may  be  regarded  as  a  revival  of  the  Permian 
activity,  culminated  in  Jurassic,  or  at  least  in  post-Newark  time, 
and  resulted  in  the  production  of  the  singular  monoclinal  atti- 
tude of  the  formation ;  and  as  far  as  I  can  correlate  it  with  the 
accompanying  change  in  the  underlying  structures,  it  involved 
there  an  over-pushing  of  the  closed  folds  of  the  Archaean  and 
Paleozoic  rocks.  This  is  illustrated  in  Figs.  12  and  13,  in  which 
the  original  and  disturbed  attitudes  of  the  Newark  and  the 


FIG.  12 


FIG.  13 


underlying  formations  are  roughly  shown,  the  over-pushing  of 
the  fundamental  folds  causing  the  monoclinal  and  probably 
faulted  structure  in  the  overlying  beds.  (See  Am.  Jour.  Set., 
XXXII  (1886),  342  ;  and  U.  S.  Geol.  Surv.,  VII Ann.  ^/.(i888), 
486.)  If  this  be  true,  we  might  suspect  that  the  unsymmetrical 
attitude  of  the  Appalachian  folds,  noted  by  Rogers  as  a  charac- 
teristic of  the  range,  is  a  feature  that  was  intensified,  if  not 
originated,  in  Jurassic  and  not  in  Permian  time. 

It  is  not  to  be  supposed  that  the  Jurassic  deformation  was 
limited  to  the  area  of  the  Newark  beds  ;  it  may  have  extended 
some  way  on  either  side ;  but  it  presumably  faded  out  at  no 
great  distance,  for  it  has  not  been  detected  in  the  history  of  the 
Atlantic  and  Mississippi  regions  remote  from  the  Newark  belt. 
In  the  district  of  the  central  folds  of  Pennsylvania,  with  which 
we  are  particularly  concerned,  this  deformation  was  probably 
expressed  in  a  further  folding  and  over-pushing  of  the  already 
partly  folded  beds,  with  rapidly  decreasing  effect  to  the  north- 
west ;  and  perhaps  also  by  slip  faults,  which  at  the  surface  of 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    425 

the  ground  nearly  followed  the  bedding  planes  ;  but  this  is  evi- 
dently hypothetical  to  a  high  degree.  The  essential  point  for 
our  subsequent  consideration  is  that  the  Jurassic  deformation 
was  probably  accompanied  by  a  moderate  elevation,  for  it  al- 
lowed the  erosion  of  the  Newark  beds  and  of  laterally  adjacent 
areas  as  well. 

Jura- Cretaceous  Denudation.  In  consequence  of  this  elevation, 
a  new  cycle  of  erosion  was  entered  upon,  which  I  shall  call 
the  Jura-Cretaceous  cycle.  It  allowed  the  accomplishment  of 
a  vast  work,  which  ended  in  the  production  of  a  general  lowland 
of  denudation,  a  wide  area  of  faint  relief,  whose  elevated  rem- 
nants are  now  to  be  seen  in  the  even  ridge  crests  that  so 
strongly  characterize  the  central  district,  as  well  as  in  certain 
other  even  uplands,  now  etched  by  the  erosion  of  a  later  cycle 
of  destructive  work.  I  shall  not  take  space  here  for  the  delib- 
erate statement  of  the  argument  leading  to  this  end,  but  its 
elements  are  as  follows :  the  extraordinarily  persistent  ac- 
cordance among  the  crest-line  altitudes  of  many  Medina  and 
Carboniferous  ridges  in  the  central  district ;  the  generally 
corresponding  elevation  of  the  western  plateau  surface,  itself  a 
surface  of  erosion,  but  now  trenched  by  relatively  deep  and 
narrow  valleys ;  the  generally  uniform  and  consistent  altitude 
of  the  uplands  in  the  crystalline  highlands  of  northern  New 
Jersey  and  in  the  South  mountains  of  Pennsylvania ;  and  the 
extension  of  the  same  general  surface,  descending  slowly  east- 
ward, over  the  even  crest  lines  of  the  Newark  trap  ridges. 
Besides  the  evidence  of  less  continental  elevation  thus  deduced 
from  the  topography,  it  may  be  noted  that  a  lower  stand  of  the 
land  in  Cretaceous  time  than  now  is  indicated  by  the  erosion 
that  the  Cretaceous  beds  have  suffered  in  consequence  of  the 
elevation  that  followed  their  deposition.  The  Cretaceous  trans- 
gression in  the  western  states  doubtless  bears  on  the  problem 
also.  Finally,  it  may  be  fairly  urged  that  it  is  more  accordant 
with  what  is  known  about  old  mountains  in  general  to  suppose 
that  their  mass  has  stood  at  different  altitudes  with  respect  to 
base-level  during  their  long  period  of  denudation  than  to  sup- 
pose that  they  have  held  one  altitude  through  all  the  time  since 
their  deformation. 


426  PHYSIOGRAPHIC  ESSAYS 

It  is  natural  enough  that  the  former  maintenance  of  some 
lower  altitude  than  the  present  should  have  expression  in  the 
form  of  the  country,  if  not  now  extinguished  by  subsequent 
erosion.  It  is  simply  the  reverse  of  this  statement  that  leads 
us  to  the  above-stated  conclusion.  We  may  be  sure  that  the 
long-maintained  period  of  relative  quiet  was  of  great  importance 
in  allowing  time  for  the  mature  adjustment  of  the  rivers  of  the 
region,  and  hence  due  account  must  be  taken  of  it  in  a  later 
section.  I  say  relative  quiet,  for  there  were  certainly  subordi- 
nate oscillations  of  greater  or  less  value ;  McGee  has  detected 
records  of  one  of  these  about  the  beginning  of  Cretaceous  time, 
but  its  effects  are  not  now  known  to  be  of  geographical  value ; 
that  is,  they  do  not  now  manifest  themselves  in  the  form  of  the 
present  surface  of  the  land,  but  only  in  the  manner  of  deposi- 
tion and  ancient  erosion  of  certain  deposits  (b}.  Another  subordi- 
nate oscillation  in  the  sense  of  a  moderate  depression  seems  to 
have  extended  through  middle  and  later  Cretaceous  time,  result- 
ing in  an  inland  transgression  of  the  sea  and  the  deposit  of  the 
Cretaceous  formation  unconformably  on  the  previous  land  sur- 
face for  a  considerable  distance  beyond  the  present  margin 
of  the  formation.  This  is  important  as  affecting  our  rivers. 
Although  these  oscillations  were  of  considerable  geological 
value,  I  do  not  think  that  for  the  present  purposes  they  call 
for  any  primary  division  of  the  Jura-Cretaceous  cycle  ;  for  as 
the  result  of  this  long  period  of  denudation  we  find  but  a  single 
record  in  the  great  lowland  of  erosion  above  described,  a  record 
of  prime  importance  in  the  geographical  development  of  our 
region  that  will  often  be  referred  to.  The  surface  of  faint 
relief  then  completed  may  be  called  the  Cretaceous  base-level 
lowland.  It  may  be  pictured  as  a  low,  undulating  plain  of  wide 
extent,  with  a  portion  of  its  Atlantic  margin  submerged  and 
covered  over  with  a  relatively  thin  marine  deposit  of  sands, 
marls,  and  clays. 

Tertiary  Elevation  and  Denudation.  This  broad  lowland  is  a 
lowland  no  longer.  It  has  been  raised  over  the  greater  part  of 
its  area  into  a  highland,  with  an  elevation  of  from  one  to  three 
thousand  feet,  sloping  gently  eastward  and  descending  under 
the  Atlantic  level  near  the  present  margin  of  the  Cretaceous 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    427 

formation.  The  elevation  seems  to  have  taken  place  early  in 
Tertiary  time,  and  will  be  referred  to  as  of  that  date.  Oppor- 
tunity was  then  given  for  the  revival  of  the  previously  exhausted 
forces  of  denudation,  and  as  a  consequence  we  now  see  the  for- 
merly even  surface  of  the  plain  greatly  roughened  by  the  incision 
of  deep  valleys  and  the  opening  of  broad  lowlands  on  its  softer 
rocks.  Only  the  harder  rocks  retain  indications  of  the  even 
surface  which  once  stretched  continuously  across  the  whole  area. 
The  best  indication  of  the  average  altitude  at  which  the  mass 
stood  through  the  greater  part  of  post-Cretaceous  time  is  to  be 
found  on  the  weak  shales  of  the  Newark  formation  in  New  Jersey 
and  Pennsylvania,  and  on  the  weak  Cambrian  limestones  of  the 
great  Kittatinny  valley;  for  both  of  these  areas  have  been  actu- 
ally almost  base-leveled  again  in  the  Tertiary  cycle.  They  will 
be  referred  to  as  the  Tertiary  base-level  lowlands  ;  and  the  valleys 
corresponding  to  them,  cut  in  the  harder  rocks,  as  well  as  the 
rolling  lowlands  between  the  ridges  of  the  central  district  of 
Pennsylvania  will  be  regarded  as  of  the  same  date.  Whatever 
variations  of  level  occurred  in  this  cycle  of  development  do  not 
seem  to  have  left  marks  of  importance  on  the  inland  surface, 
though  they  may  have  had  greater  significance  near  .the  coast. 

Later  Changes  of  Level.  Again  at  the  close  of  Tertiary  time, 
there  was  an  elevation  of  moderate  amount,  and  to  this  may  be 
referred  the  trenches  that  are  so  distinctly  cut  across  the  Ter- 
tiary base-level  lowland  by  the  larger  rivers,  as  well  as  the  lateral 
shallower  channels  of  the  smaller  streams.  This  will  be  called 
the  Quaternary  cycle  ;  and  for  the  present  no  further  mention  of 
the  oscillations  known  to  have  occurred  in  this  division  of  time 
need  be  considered ;  the  reader  may  find  careful  discussion  of 
them  in  the  paper  by  McGee,  above  referred  to.  It  is  proper 
that  I  should  add  that  the  suggestion  of  base-leveling  both  of 
the  crest  lines  and  of  the  lowlands,  which  I  have  found  so  profit- 
able in  this  and  other  work,  is  due  largely  to  personal  conference 
with  Messrs.  Gilbert  and  McGee  of  the  Geological  Survey ;  but 
it  is  not  desired  to  make  them  in  any  way  responsible  for  the 
statements  here  given. 

Illustrations  of  Pennsylvanian  Topography.  A  few  sketches 
made  during  a  recent  recess  trip  with  several  students  through 


428 


PHYSIOGRAPHIC  ESSAYS 


Pennsylvania  may  be  introduced  in  this  connection.  The  first 
(Fig.  14)  is  a  view  from  Jenny  Jump  mountain,  on  the  north- 
western side  of  the  New  Jersey  highlands,  looking  northwest 
across  the  Kittatinny  valley  lowland  to  Blue,  or  Kittatinny, 
mountain,  where  it  is  cut  at  the  Delaware  Water  Gap.  The 


FIG. 14 

extraordinarily  level  crest  of  the  mountain  preserves  record  of 
the  Cretaceous  base-level  lowland ;  since  the  elevation  of  this 
ancient  lowland,  its  softer  rocks  have,  as  it  were,  been  etched 
out,  leaving  the  harder  ones  in  relief ;  thus  the  present  valley 
lowland  is  to  be  explained.  In  consequence  of  the  still  later 
elevation  of  less  amount,  the  Delaware  has  cut  a  trench  m  the 
present  lowland  which  is  partly  seen  to  the  left  in  the  sketch. 
Fig.  1 5  is  a  general  view  of  the  Lehigh  plateau  and  canon,  look- 
ing south  from  Bald  mountain  just  above  Penn  Haven  Junction. 


FIG. 15 

Blue  mountain  is  the  most  distant  crest,  seen  for  a  little  space. 
The  ridges  near  and  above  Mauch  Chunk  form  the  other  out- 
lines, all  rising  to  an  astonishingly  even  altitude,  in  spite  of  their 
great  diversity  of  structure.  Before  the  existing  valleys  were 
excavated,  the  upland  surface  must  have  been  an  even  plain,  — 
the  Cretaceous  base-level  lowland  elevated  into  a  plateau.  The 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    429 

valleys  cut  into  the  plateau  during  the  Tertiary  cycle  are  nar- 
row here  because  the  rocks  are  mostly  hard.  The  steep  slopes 
of  the  canon-like  valley  of  the  Lehigh  and  the  even  crests  of 
the  ridges  manifestly  belong  to  different  cycles  of  development. 
Figs.  1 6  and  17  are  gaps,  cut  in  Black  Log  and  Shade  mountains 


FIG.  1 6 

by  a  small  upper  branch  stream  of  the  Juniata  in  southeastern 
Huntingdon  county.  The  stream  traverses  a  breached  anticlinal 
of  Medina  sandstone,  of  which  these  mountains  are  the  lateral 
members.  A  long,  narrow  valley  is  opened  on  the  axial  Trenton 
limestone  between  the  two.  The  gaps  are  not  opposite  to  each 
other,  and  therefore  in  looking  through  either  gap  from  the 
outer  country  the  even  crest  of  the  further  ridge  is  seen  beyo.nd 
the  axial  valley.  The  gap  in  Black  Log  mountain  (Fig.  16)  is 


FIG.  17 

located  on  a  small  fracture,  but  in  this  respect  it  is  unlike  most 
of  its  fellows.  (See  Second  Geol.  Surv.  Pa.,  Report  T3,  19.)  The 
striking  similarity  of  the  two  views  illustrates  the  uniformity 
that  so  strongly  characterizes  the  Medina  ridges  of  the  central 
district.  Fig.  1 8  is  in  good  part  an  ideal  view,  based  on  sketches 
on  the  upper  Susquehanna,  and  designed  to  present  a  typical 


430 


PHYSIOGRAPHIC  ESSAYS 


illustration  of  the  more  significant  features  of  the  region.  It 
shows  the  even  crest  lines  of  a  high  Medina  or  Pocono  ridge  in 
the  background,  retaining  the  form  given  to  it  in  the  Cretaceous 
cycle  ;  the  even  lowlands  in  the  foreground,  opened  on  the  weaker 
Siluro-Devonian  rocks  in  the  Tertiary  cycle  ;  and  the  uneven 
ridges  in  the  middle  distance  marking  the  Oriskany  and  Chemung 
beds  of  intermediate  hardness  that  have  lost  the  Cretaceous 


FIG.  1 8 

level  and  yet  have  not  been  reduced  to  the  Tertiary  lowland. 
The  Susquehanna  flows  distinctly  below  the  lowland  plain,  and 
the  small  side  streams  run  in  narrow  trenches  of  late  Tertiary 
and  Quaternary  date. 

If  this  interpretation  is  accepted,  and  the  Permian  mountains 
are  seen  to  have  been  once  greatly  reduced  and  at  a  later  time 
worn  out,  while  the  ridges  of  to-day  are  merely  the  relief  left  by 
the  etching  of  Tertiary  valleys  in  a  Cretaceous  base-level  low- 
land, then  we  may  well  conclude  with  Lowell  that  "  mountains 
cannot  remain  long  as  mountains ;  they  are  ephemeral  topo- 
graphic forms"  (b,  196). 


III.    GENERAL  CONCEPTION  OF  THE  HISTORY  OF  A  RIVER 

The  Complete  Cycle  of  River  Life:  Youth,  Adolescence ',  Matu- 
rity, and  Old  Age.  The  general  outline  of  an  ideal  river's  history 
may  now  be  considered,  preparatory  to  examining  the  special 
history  of  the  rivers  of  Pennsylvania  as  controlled  by  the  geo- 
logical events  just  narrated. 

Rivers  are  so  long-lived  and  survive  with  more  or  less  modifi- 
cation so  many  changes  in  the  attitude  and  even  in  the. structure 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    431 

of  the  land,  that  the  best  way  of  entering  on  their  discussion  seems 
to  be  to  examine  the  development  of  an  ideal  river  of  simple  his- 
tory, and  from  the  general  features  thus  discovered,  it  may  then 
be  possible  to  unravel  the  complex  sequence  of  events  that  lead 
to  the  present  condition  of  actual  rivers  of  complicated  history. 

A  river  that  is  established  on  a  new  land  may  be  called  an 
original  river.  It  must  at  first  be  of  the  kind  known  as  a  con- 
sequent river,  for  it  has  no  ancestor  from  which  to  be  derived. 
Examples  of  simple  original  rivers  may  be  seen  in  young  plains, 
of  which  southern  New  Jersey  furnishes  a  fair  illustration.  Ex- 
amples of  essentially  original  rivers  may  be  seen  also  in  regions 
of  recent  and  rapid  displacement,  such  as  the  Jura  or  the  broken 
country  of  southern  Idaho,  where  the  directly  consequent  char- 
acter of  the  drainage  leads  us  to  conclude  that,  if  any  rivers 
occupied  these  regions  before  their  recent  deformation,  they 
were  so  completely  extinguished  by  the  newly  made  slopes  that 
we  see  nothing  of  them  now. 

Once  established,  an  original  river  advances  through  its  long 
life,  manifesting  certain  peculiarities  of  youth,  maturity,  and  old 
age,  by  which  its  successive  stages  of  growth  may  be  recog- 
nized without  much  difficulty.  For  the  sake  of  simplicity,  let  us 
suppose  the  land  mass,  on  which  an  original  river  has  begun  its 
work,  stands  perfectly  still  after  its  first  elevation  or  deformation, 
and  so  remains  until  the  river  has  completed  its  task  of  carrying 
away  all  the  mass  of  rocks  that  rise  above  its  base-level.  The 
lapse  of  time  will  be  called  a  cycle  in  the  life  of  a  river.  A  com- 
plete cycle  is  a  long  measure  of  time  in  regions  of  great  eleva- 
tion or  of  hard  rocks  ;  but  whether  or  not  any  river  ever  passed 
through  a  single  cycle  of  life  without  interruption  we  need  not 
now  inquire.  Our  purpose  is  only  to  learn  what  changes  it 
would  experience  if  it  did  thus  develop  steadily  from  infancy 
to  old  age  without  disturbance. 

In  its  infancy  the  river  drains  its  basin  imperfectly,  for  it  is 
then  embarrassed  by  the  original  inequalities  of  the  surface,  and 
lakes  collect  in  all  the  depressions.  At  such  time  the  ratio  of 
evaporation  to  rainfall  is  relatively  large,  and  the  ratio  of  trans- 
ported land  waste  to  rainfall  is  small.  The  channels  followed  by 
the  streams  that  compose  the  river  as  a  whole  are  narrow  and 


432  PHYSIOGRAPHIC  ESSAYS 

shallow,  and  their  number  is  small  compared  to  that  which  will 
be  developed  at  a  later  stage.  The  divides  by  which  the  side 
streams  are  separated  are  poorly  marked,  and  in  level  countries 
are  surfaces  of  considerable  area  and  not  lines  at  all.  It  is  only 
in  the  later  maturity  of  a  system  that  the  divides  are  reduced  to 
lines  by  the  consumption  of  the  softer  rocks  on  either  side.  The 
difference  between  constructional  forms  and  these  forms  that 
are  due  to  the  action  of  denuding  forces  is  in  a  general  way  so 
easily  recognized  that  immaturity  and  maturity  of  a  drainage 
area  can  be  readily  discriminated.  In  the  truly  infantile  drainage 
system  of  the  Red  River  of  the  North,  the  interstream  areas  are 
so  absolutely  flat  that  water  collects  on  them  in  wet  weather, 
not  having  either  original  structural  slope  or  subsequently  devel- 
oped denuded  slope  to  lead  it  to  the  streams.  On  the  almost 
equally  young  lava  blocks  of  southern  Oregon,  the  well-marked 
slopes  are  as  yet  hardly  channeled  by  the  flow  of  rain  down  them, 
and  the  depressions  among  the  tilted  blocks  are  still  undrained, 
unfilled  basins. 

As  the  river  becomes  adolescent,  its  channels  are  deepened 
and  all  the  larger,  ones  descend  close  to  base-level.  If  local  con- 
trasts of  hardness  allow  a  quick  deepening  of  the  downstream 
part  of  the  channel,  while  the  part  next  upstream  resists  erosion, 
a  cascade  or  waterfall  results  ;  but,  like  the  lakes  of  earlier  youth, 
it  is  evanescent  and  endures  but  a  small  part  of  the  whole  cycle 
of  growth  ;  but  the  falls  on  the  small  headwater  streams  of  a 
large  river  may  last  into  its  maturity,  just  as  there  are  young 
twigs  on  the  branches  of  a  large  tree.  With  the  deepening  of 
the  channels,  there  comes  an  increase  in  the  number  of  gulleys 
on  the  slopes  of  the  channel ;  the  gulleys  grow  into  ravines  and 
these  into  side  valleys,  joining  their  master  streams  at  right 
angles  (La  Noe  and  Margerie).  With  their  continued  develop- 
ment the  maturity  of  the  system  is  reached  ;  it  is  marked  by  an 
almost  complete  acquisition  of  every  part  of  the  original  con- 
structional surface  by  erosion  under  the  guidance  of  the  streams, 
so  that  every  drop  of  rain  that  falls  finds  a  way  prepared  to  lead 
it  to  a  stream  and  then  to  the  ocean,  its  goal.  The  lakes  of  initial 
imperfection  have  long  since  disappeared ;  the  waterfalls  of 
adolescence  have  been  worn  back,  unless  on  the  still  young 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    433 

headwaters.  With  the  increase  of  the  number  of  side  streams, 
ramifying  into  all  parts  of  the  drainage  basin,  there  is  a  propor- 
tionate increase  in  the  surface  of  the  valley  slopes,  and  with  this 
comes  an  increase  in  the  rate  of  waste  under  atmospheric  forces  ; 
hence  it  is  at  maturity  that  the  river  receives  and  carries  the 
greatest  load ;  indeed,  the  increase  may  be  carried  so  far  that 
the  lower  trunk  stream,  of  gentle  slope  in  its  early  maturity,  is 
unable  to  carry  the  load  brought  to  it  by  the  upper  branches,  and 
therefore  resorts  to  the  temporary  expedient  of  laying  it  aside  in 
a  flood  plain.  The  level  of  the  flood  plain  is  sometimes  built  up 
faster  than  the  small  side  streams  of  the  lower  course  can  fill 
their  valleys,  and  hence  they  are  converted  for  a  little  distance 
above  their  mouths  into  shallow  lakes.  The  growth  of  the  flood 
plain  also  results  in  carrying  the  point  of  junction  of  tributaries 
farther  and  farther  downstream,  and  at  last  in  turning  lateral 
streams  aside  from  the  main  stream,  sometimes  forcing  them  to 
follow  independent  courses  to  the  sea  (Lombardini).  But  although 
thus  separated  from  the  main  trunk,  it  would  be  no  more  rational 
to  regard  such  streams  as  independent  rivers  than  it  would  be  to 
regard  the  branch  of  an  old  tree,  now  fallen  to  the  ground  in  the 
decay  of  advancing  age,  as  an  independent  plant ;  both  are  de- 
tached portions  of  a  single  individual,  from  which  they  have  been 
separated  in  the  normal  processes  of  growth  and  decay. 

In  the  later  and  quieter  old  age  of  a  river  system,  the  waste  of 
the  land  is  yielded  more  slowly  by  reason  of  the  diminishing  slopes 
of  the  valley  sides  ;  then  the  headwater  streams  deliver  less  detri- 
tus to  the  main  channel,  which,  thus  relieved,  turns  to  its  post- 
poned task  of  carrying  its  former  excess  of  load  to  the  sea,  and 
cuts  terraces  in  its  flood  plain,  preparatory  to  sweeping  it  away. 
It  does  not  always  find  the  buried  channel  again,  and  perhaps 
settling  down  on  a  low  spur  a  little  to  one  side  of  its  old  line,  pro- 
duces a  rapid  or  a  low  fall  on  the  lower  slope  of  such  an  obstruction 
(Penck).  Such  courses  may  be  called  locally  superimposed. 

It  is  only  during  maturity  and  for  a  time  before  and  after- 
wards that  the  three  divisions  of  a  river,  commonly  recognized, 
appear  most  distinctly  ;  the  torrent  portion  being  the  still  young 
headwater  branches,  growing  by  gnawing  backwards  at  their 
sources ;  the  valley  portion  proper,  where  longer  time  of  work 


434  PHYSIOGRAPHIC  ESSAYS 

has  enabled  the  valley  to  obtain  a  greater  depth  and  width  ;  and 
the  lower  flood-plain  portion,  where  the  temporary  deposition  of 
the  excess  of  load  is  made  until  the  activity  of  middle  life  is  past. 

"  Maturity  "  seems  to  be  a  proper  term  to  apply  to  this  long- 
enduring  stage  ;  for  as  in  organic  forms,  where  the  term  first 
came  into  use,  it  here  also  signifies  the  highest  development  of 
all  functions  between  a  youth  of  endeavor  towards  better  work 
and  an  old  age  of  relinquishment  of  fullest  powers.  It  is  the 
mature  river  in  which  the  rainfall  is  best  led  away  to  the  sea, 
and  which  carries  with  it  the  greatest  load  of  land  waste ;  it  is 
at  maturity  that  the  regular  descent  and  steady  flow  of  the  river 
is  best  developed,  being  the  least  delayed  in  lakes  and  least  over- 
hurried  in  impetuous  falls. 

Maturity  past,  and  the  power  of  the  river  is  on  the  decay. 
The  relief  of  the  land  diminishes,  for  the  streams  no  longer 
deepen  their  valleys,  although  the  hill-tops  are  degraded  ;  and 
with  the  general  loss  of  elevation,  there  is  a  failure  of  rainfall 
to  a  certain  extent ;  for  it  is  well  known  that  up  to  certain 
considerable  altitudes  rainfall  increases  with  height.  A  hyeto- 
graphic  and  a  hypsometric  map  of  a  country  for  this  reason 
show  a  marked  correspondence.  The  slopes  of  the  headwaters 
decrease  and  the  valley  sides  widen  so  far  that  the  land  waste 
descends  from  them  more  slowly  than  before.  Later,  what  with 
failure  of  rainfall  and  decrease  of  slope,  there  is  perhaps  a 
return  to  the  early  imperfection  of  drainage,  and  the  number  of 
side  streams  diminishes  as  branches  fall  from  a  dying  tree. 
The  flood  plains  of  maturity  are  carried  down  to  the  sea,  and  at 
last  the  river  settles  down  to  an  old  age  of  well-earned  rest  with 
gentle  flow  and  light  load,  little  work  remaining  to  be  done. 
The  great  task  that  the  river  entered  upon  is  completed. 

Mutual  Adjustment  of  River  Courses.  In  certain  structures, 
chiefly  those  of  mountainous  disorder  on  which  the  streams  are 
at  first  high  above  base-level,  there  is  a  process  of  adjustment 
extremely  characteristic  of  quiet  river  development,  by  which 
the  down-hill  courses  that  were  chosen  in  early  life,  and  as  we 
may  say  unadvisedly  and  with  the  heedlessness  and  little  fore- 
sight of  youth,  are  given  up  for  others  better  fitted  for  the 
work  of  the  mature  river  system.  A  change  of  this  kind  happens 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    435 

when  the  young  stream,  taking  the  lowest  line  for  its  guide, 
happens  to  flow  on  a  hard  bed  at  a  considerable  height  above 
base-level,  while  its  branches  on  one  side  or  the  other  have 
opened  channels  on  softer  beds  ;  a  part  of  the  main  channel 
may  then  be  deserted  by  the  withdrawal  of  its  upper  waters  to 
a  lower  course  by  way  of  a  side  stream.  The  change  to  better 
adjustment  also  happens  when  the  initial  course  of  the  main 
stream  is  much  longer  than  a  course  that  may  be  offered  to 
its  upper  portion  by  the  backward  gnawing  of  an  adjacent 
stream  (Lowl,  Penck).  Sometimes  the -lateral  cutting  or  plana- 
tion  that  characterizes  the  main  trunk  of  a  mature  river  gives  it 
possession  of  an  adjacent  smaller  stream  whose  bed  is  at  a  higher 
level  (Gilbert).  A  general  account  of  these  processes  may  be 
found  in  Philippson's  serviceable  "  Studien  iiber  Wasserscheiden" 
(Leipzig,  1886).  This  whole  matter  is  of  much  importance  and 
deserves  deliberate  examination.  It  should  be  remembered  that 
changes  in  river  courses  of  the  kind  now  referred  to  are  un- 
connected with  any  external  disturbance  of  the  river  basin, 
and  are  purely  normal  spontaneous  acts  during  advancing 
development.  Two  examples,  pertinent  to  our  special  study, 
will  be  considered. 

Let  AB  (Fig.  19)  be  a  stream  whose  initial  consequent  course 
led  it  down  the  gently  sloping  axial  trough  of  a  syncline.  The 
constructional  surface  of  the  syncline  is  shown  by  contours.  Let 
the  succession  of  beds  to  be  discovered  by  erosion  be  indicated 
in  a  section,  laid  in  proper  position  on  the  several  diagrams,  but 
revolved  into  the  horizontal  plane,  the  harder  beds  being  dotted 
and  the  base-level  standing  at  OO.  Small  side  streams  will  soon 
be  developed  on  the  slopes  of  the  syncline  in  positions  deter- 
mined by  cross-fractures  or  more  often  by  what  we  call  accident ; 
the  action  of  streams  in  similar  synclines  on  the  outside  of  the 
inclosing  anticlines  will  be  omitted  for  the  sake  of  simplicity. 
In  time  the  side  streams  will  cut  through  the  harder  upper  bed 
J/and  enter  the  softer  bed  N,  on  which  longitudinal  channels, 
indicated  by  hachures,  will  be  extended  along  the  strike  (Fig.  20) 
(La  Noe  and  Marge rie).  Let  these  be  called  "  subsequent " 
streams.  Consider  two  side  streams  of  this  kind,  C  and  D, 
heading  against  each  other  at  E,  one  joining  the  main  stream 


436 


PHYSIOGRAPHIC   ESSAYS 


lower  down  the  axis  of  the  syncline  than  the  other.  The 
headwaters  of  C  will  rob  the  headwaters  of  D,  because  the  deep- 
ening of  the  channel  of  D  is  retarded  by  its  having  to  join  the 
main  stream  at  a  point  where  the  hard  bed  in  the  axis  of  the  fold 
holds  the  main  channel  well  above  base-level.  The  notch  cut  by 
D  will  then  be  changed  from  a  water  gap  to  a  wind  gap,  and  the 
upper  portion  of  D 
will  find  exit  through 
the  notch  cut  by  C,  as 
in  Fig.  21.  As  other 
subsequent  head- 
waters make  capture 
of  C,  the  greater  depth 
to  which  the  lateral 
valley  is  cut  on  the 
soft  rock  causes  a 
slow  migration  of  the 
divides  in  the  aban- 
doned gaps  towards 
the  main  stream,  and 
before  long  the  upper 
part  of  the  main 
stream  itself  will  be 
led  out  of  the  syn- 
clinal axis  to  follow 
the  monoclinal  valley 
at  one  side  for  a  dis- 
tance (Fig.  22),  until 
the  axis  can  be  re- 
joined through  the 
gap  where  the  axial 
portion  of  the  controlling  hard  bed  is  near  or  at  base-level. 
The  upper  part  •  of  the  synclinal  trough  will  then  be  attacked 
by  under-cutting  on  the  slope  of  the  quickly  deepened  channels 
of  the  lateral  streams,  and  the  hard  bed  will  be  worn  away  in 
the  higher  part  of 'the  axis  before  it  is  consumed  in  the  lower 
part.  The  location  of  the  successful  lateral  stream  on  one  or  the 
other  side  of  the  syncline  may  be  determined  by  the  dip  of 


FIG.  19 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    437 


the  beds,  gaps  being  cut  quicker  on  steep  than  on  gentle  dips. 
If  another  hard  bed  is  encountered  below  the  soft  one,  the  proc- 
ess will  be  repeated  ;  and  the  mature  arrangement  of  the  streams 
will  be  as  in  Fig.  23  (on  a  smaller  scale  than  the  preceding), 
running  obliquely  off  the  axis  of  the  fold  where  a  hard  bed  of 
the  syncline  rises  above  base-level,  and  returning  to  the  axis 


FIG. 21 


FIG. 22 


FIG. 23 


where  the  hard  bed  is  below  or  at  base-level ;  a  monoclinal 
stream  wandering  gradually  from  the  axis  along  the  strike  of 
the  soft  bed  AE,  by  which  the  side  valley  is  located,  and  return- 
ing abruptly  to  the  axis  by  a  cataclinal l  stream  in  a  transverse 

1  See  the  terminology  suggested  by  Powell,  Exploration  of  the  Colorado  River 
of  the  West  (1875),  160.  This  terminology  is  applicable  only  to  the  most  detailed 
study  of  our  rivers,  by  reason  of  their  crossing  so  many  folds  and  changing  so 
often  from  longitudinal  to  transverse  courses. 


438 


PHYSIOGRAPHIC  ESSAYS 


gap  EB  in  the  next  higher  hard  bed,  and  there  rejoining  the 
diminished  representative  or  survivor  of  the  original  axial  or 
synclinal  stream  GB. 

Terminology  of  Rivers  changed  by  Adjustment.  A  special 
terminology  is  needed  for  easy  reference  to  the  several  parts  of 
the  streams  concerned  in  such  an  adjustment.  Let  AB  and 
CD  (Fig.  24)  be  streams  of  unequal  size  cutting  gaps  H  and  G 
in  a  ridge  that  lies  transverse  to  their  course.  CD  being  larger 
than  AB  will  deepen  its  gap  faster.  Of  two  subsequent  streams, 
JE  and  JF,  growing  on  the  upstream  side  of  the  ridge,  JE  will 

have  the  steeper 
slope,  because  it 
joins  the  deeper 
master  stream. 
The  divide  J  will 
therefore  be  driven 
toward  AB,  and  if 
all  the  conditions 
concerned  conspire 
favorably,  JE  will 
at  last  tap  AB  at 
F,  and  lead  the  upper  part,  AF,  out  by  the  line  FEGD  (Fig.  25) 
through  the  deeper  gap  G.  We  may  then  say  that  JE  becomes 
the  divertor  of  AF,  which  is  diverted;  and  when  the  process 
is  completed,  by  the  transfer  of  the  divide  from/,  on  the  soft 
rocks,  to  a  stable  location, H,  on  the  hard  rocks,  there  will  be  a 
short  inverted  stream  HF\  while  HB  is  the  remaining  behe&ded 
portion  of  the  original  stream  AB,  and  the  water  gap  of  AB 
becomes  a  wind  gap,  H.  It  is  very  desirable  that  geographical 
exploration  should  discover  examples  of  the  process  of  adjust- 
ment in  its  several  stages.  The  preparatory  stage  is  easily  rec- 
ognized by  the  difference  in  the  size  of  the  two  main  streams, 
the  difference  in  the  depth  of  their  gaps,  and  the  unsymmetrical 
position  of  the  divide  J.  The  very  brief  stage  of  transition  gives 
us  the  rare  examples  of  bifurcating  streams.  For  a  short  time 
after  capture  of  the  diverted  stream  by  the  divertor,  the  new  divide 
will  lie  between  F  and  H,  in  an  unstable  position,  the  duration 
of  this  time  depending  on  the  energy  of  the  process  of  capture. 


FIG.  25 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    439 

The  consequences  resulting  from  readjustments  of  this  kind, 
by  which  their  recent  occurrence  can  be  detected,  are  :  a  rela- 
tively sudden  increase  of  volume  of  the  divertor  and  hence  a 
rapid  deepening  of  the  course  of  the  diverting  stream  FE,  and  of 
the  diverted  AF,  near  the  point  of  capture ;  small  side  streams 
of  these  two  being  unable  to  keep  pace  with  this  change  will  join 
their  masters  in  local  rapids,  which  work  upstream  gradually 
and  fade  away  (Lowl,  Penck,  McGee).  The  expanded  portion 
ED  of  the  larger  stream  CD,  already  of  faint  slope,  may  be 
locally  overcome  for  a  time  with  the  increase  of  detritus  that 
will  be  thus  delivered  to  it  at  the  entrance  E  of  the  divertor ; 
while  the  beheaded  stream  HB  will  find  itself  embarrassed  to 
live  up  to  the  habits  of  its  large  valley  (Heim).  Geographical 
exploration  with  these  matters  in  mind  offers  opportunity  for 
the  most  attractive  discoveries. 

Examples  of  Adjustment.  Another  case  is  roughly  figured  in 
the  next  three  diagrams  (Figs.  26,  27,  28).  Two  adjacent  syn- 
clinal streams,  EA  and  HB,  join  a  transverse  master  stream,  C, 
but  the  synclines  are  of  different  forms  ;  the  surface  axis  of  one, 
EA,  stands  at  some  altitude  above  base-level  until  it  nearly 
reaches  the  place  of  the  transverse  stream ;  while  the  axis  of 
the  other,  HB,  descends  near  base-level  at  a  considerable  dis- 
tance from  the  transverse  stream.  As  lateral  valleys  E  and  D 
are  opened  on  the  anticline  between  the  synclines  by  a  process 
similar  to  that  already  described,  the  divide  separating  them 
will  shift  towards  the  stream  of  fainter  slope,  that  is,  towards 
the  'syncline  EA,  whose  axis  holds  its  hard  beds  above  base- 
level  ;  and  in  time  the  upper  part  of  the  main  stream  will  be 
withdrawn  from  this  syncline  to  follow  an  easier  course  by 
crossing  to  the  other,  as  in  Fig.  27.  If  the  elevation  of  the  syn- 
clinal axis  AES  take  the  shape  of  a  long,  flat  arch,  descending 
at  the  farther  end  into  a  synclinal  lake  basin,  S,  whose  outlet 
is  along  the  arching  axis  SA,  then  the  mature  arrangement  of 
stream  courses  will  lead  the  lake  outlet  away  from  the  axis  by 
some  gap  in  the  nearer  ascending  part  of  the  arch  where  the 
controlling  hard  bed  falls  near  to  base-level,  as  at  F  (Fig.  28), 
and  will  take  it  by  some  subsequent  course,  FD,  across  the  low- 
land that  is  opened  on  the  soft  beds  between  the  synclines,  and 


440 


PHYSIOGRAPHIC  ESSAYS 


carry  it  into  the  lower  syncline  HB,  at  Dy  where  the  hard  beds 
descend  below  base-level. 

The  variety  of  adjustments  following  the  general  principle  here 
indicated  is  infinite.  Changes  of  greater  or  less  value  are  thus 
introduced  in  the  initial  drainage  areas,  until,  after  attaining  an 
attitude  of  equilibrium,  further  change  is  arrested,  or  if  occurring, 


FIG.  27 


is  relatively  insignificant.  It  should  be  noticed  that  the  new  stream 
courses  thus  chosen  are  not  named  by  any  of  the  terms  now  cur- 
rent to  express  the  relation  of  stream  and  land  history  ;  they  are 
neither  consequent,  antecedent,  nor  superimposed.  The  stream  is 
truly  still  an  original  stream,  although  no  longer  young ;  but  its 
channel  is  not  in  all  parts  strictly  consequent  on  the  initial  construc- 
tional form  of  the  land  that  it  drains.  Streams  thus  rearranged 
may  therefore  be  named  original  streams  of  mature  adjustment. 


THE  RIVERS  AND  VALLEYS  OF   PENNSYLVANIA 


44 1 


It  should  be  clearly  recognized  that  the  process  of  adjustment 
is  a  very  slow  one,  unless  measured  in  the  extremely  long  units 
of  a  river's  life.  It  progresses  no  faster  than  the  weathering 
away  of  the  slopes  of  a  divide,  and  here  as  a  rule  weathering  is 
deliberate  to  say  the  least,  unless  accelerated  by  a  fortunate 
combination  of  favoring  conditions.  Among  these  conditions, 
great  altitude  of  the  mass  exposed  to  erosion  stands  first,  and 
deep  channeling  of  streams  below  the  surface  —  that  is,  the  ado- 
lescent stage  of  drainage  development  —  stands  second.  The 
opportunity  for  the  lateral  migration  of  a  divide  will  depend  on 
the  inequality  of  the  slopes  on  its  two  sides,  and  here  the  most 
important  factors  are  length  of  the  two  opposite  stream  courses 
from  the  water  parting  to  the  common  base-level  of  the  two,  and 
inequality  of  structure  by  which  one  stream  may  have  an  easy 
course  and  the  other  a  hard  one.  It  is  manifest  that  all  these 
conditions  for  active  shifting  of  divides  are  best  united  in  young 
and  high  mountain  ranges,  and  hence  it  is  that  river  adjustments 
have  been  found  and  studied  more  in  the  Alps  than  elsewhere. 

Revival  of  Rivers  by  Elevation  and  Drowning  by  Depression. 
I  make  no  contention  that  any  river  in  the  world  ever  passed 
through  a  simple  uninterrupted  cycle  of  the  orderly  kind  here 
described ;  but  by  examining  many  rivers,  some  young  and 
some  old,  I  do  not  doubt  that  this  portrayal  of  the  ideal  would 
be  found  to  be  fairly  correct  if  opportunity  were  offered  for  its 
development.  The  intention  of  the  sketch  'is  simply  to  prepare 
the  way  for  the  better  understanding  of  our  actual  rivers  of 
more  complicated  history. 

At  the  close  or  at  any  time  during  the  passage  of  an  initial 
cycle  such  as  the  one  just  considered,  the  drainage  area  of  a 
river  system  may  be  bodily  elevated.  The  river  is  then  turned 
back  to  a  new  youth  and  enters  a  new  cycle  of  development. 
This  is  an  extremely  common  occurrence  with  rivers,  whose  life 
is  so  long  that  they  commonly  outlive  the  duration  of  a  quies- 
cent stage  in  the  history  of  the  land.  Such  rivers  may  be  called 
revived.  Examples  may  be  given  in  which  streams  are  now  in 
their  second  or  third  period  of  revival,  the  elevations  that 
separate  their  cycles  following  so  soon  that  but  little  work  was 
accomplished  in  the  quiescent  intervals. 


442 


PHYSIOGRAPHIC  ESSAYS 


The  antithesis  of  this  is  the  effect  of  depression,  by  which  the 
lower  course  may  be  drowned,  flooded,  or  f  jorded.  This  change 
is,  if  slow,  favorable  to  the  development  of  flood  plains  in  the 
lower  course  ;  but  it  is  not  essential  to  their  production.  If  the 
change  is  more  rapid,  open  estuaries  are  formed,  to  be  trans- 
formed to  delta  lowlands  later  on. 

Opportunity  for  New  Adjustments  with  Revival.  One  of  the 
most  common  effects  of  the  revival  of  a  river  by  general  eleva- 
tion is  a  new  adjustment  of  its  course  to  a  greater  or  less  extent, 
as  a  result  of  the  new  relation  of  base-level  to  the  hard  and  soft 
beds  on  which  the  streams  had  adjusted  themselves  in  the  previous 
cycle.  Synclinal  mountains  are  most  easily  explained  as  results 
of  drainage  changes  of  this  kind  (Science,  December  21,  1888). 

Streams  thus  rearranged  may  be  said 
to  be  adjusted  through  elevation  or 
revival.  It  is  to  be  hoped  that,  as  our 
study  advances,  single  names  of  brief 
and  appropriate  form  may  replace 
these  paraphrases  ;  but  at  present  it 
seems  advisable  to  keep  the  desired 
idea  before  the  mind  by  a  descriptive 
phrase,  even  at  the  sacrifice  of  brev- 
ity. A  significant  example  may  be 
described. 

Let  it  be  supposed  that  an  origi- 
nally consequent  river  system  has 
lived  into  advanced  maturity  on  a 
surface  whose  structure  is,  like  that 
of  Pennsylvania,  composed  of  closely 
adjacent  anticlinal  and  synclinal  folds 
with  rising  and  falling  axes,  and  that 
a  series  of  particularly  resistant  beds 
composes  the  upper  members  of  the 
folded  mass.  The  master  stream  A 
(Fig.  29)  at  maturity  still  resides 
where  the  original  folds  were  lowest,  but  the  side  streams  have 
departed  more  or  less  from  the  axes  of  the  synclinals  that  they 
first  followed,  in  accordance  with  the  principles  of  adjustment 


FIG.  29 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    443 

presented  above.  The  relief  of  the  surface  is  moderate,  except 
around  the  synclinal  troughs,  where  the  rising  margins  of  the 
hard  beds  still  appear  as  ridges  of  more  or  less  prominence.  The 
minute  hachures  in  Fig.  29  are  drawn  on  the  outcrop  side  of 
these  ridges.  Now  suppose  a  general  elevation  of  the  region, 
lifting  the  synclinal  troughs  of  the  hard  beds  up  to  base-level 
or  even  somewhat  above  it.  The  deepening  of  the  revived  master 
stream  will  be  greatly  retarded  by 
reason  of  its  having  to  cross  so  many 
outcrops  of  the  hard  beds,  and  thus 
excellent  opportunity  will  be  given 
for  readjustment  by  the  growth  of 
some  diverting  stream,  B,  whose  be- 
ginning on  adjacent  softer  rocks  was 
already  made  in  the  previous  cycle. 
This  will  capture  the  main  river  at 
some  upstream  point,  and  draw  it 
nearly  all  away  from  its  hard  path 
across  the  synclinal  troughs  to  an 
easier  path  across  the  lowlands  that 
had  been  opened  on  the  underlying 
softer  beds,  leaving  only  a  small  be- 
headed remnant  in  the  lower  course. 
The  final  rearrangement  may  be 
indicated  in  Fig.  30.  It  should  be 
noted  that  every  capture  of  branches 
of  the  initial  main  stream  made  by 
the  diverting  stream  adds  to  its  abil- 
ity for  further  encroachments,  for 
with  increase  of  volume  the  channel 
is  deepened  and  a  flatter  slope  is  assumed,  and  the  whole  process 
of  pushing  away  the  divides  is  thereby  accelerated.  In  general 
it  may  be  said  that  the  larger  the  stream  and  the  less  its  eleva- 
tion above  base-level,  the  less  likely  is  it  to  be  diverted,  for 
with  large  volume  and  small  elevation  it  will  early  cut  down  its 
channel  so  close  to  base-level-  that  no  other  stream  can  offer 
it  a  better  course  to  the  sea ;  it  may  also  be  said  that,  as  a  rule, 
of  two  equal  streams,  the  headwaters  of  the  one  having  a  longer 


FIG.  30 


444  PHYSIOGRAPHIC  ESSAYS 

or  a  harder  course  will  be  diverted  by  a  branch  of  the  stream  on 
the  shorter  or  easier  course.  Every  case  must  therefore  be  ex- 
amined for  itself  before  the  kind  of  rearrangement  that  may  be 
expected  or  that  may  have  already  taken  place  can  be  discovered. 

Antecedent  and  Superimposed  Rivers.  It  not  infrequently  hap- 
pens that  the  surface,  on  which  a  drainage  system  is  more  or 
less  fully  developed,  suffers  deformation  by  tilting,  folding,  or 
faulting.  Then,  in  accordance  with  the  rate  of  disturbance,  and 
dependent  on  the  size  and  slope  of  the  streams  and  the  resistance 
of  the  rocks,  the  streams  will  be  more  or  less  rearranged,  some 
of  the  larger  ones  persisting  in  their  courses  and  cutting  their 
channels  down  almost  as  fast  as  the  mass  below  them  is  raised 
and  offered  to  their  action.  It  is  manifest  that  streams  of  large 
volume  and  considerable  slope  are  the  ones  most  likely  to  per- 
severe in  this  way,  while  small  streams  and  larger  ones  of  mod- 
erate slope  may  be  turned  from  their  former  courses  to  new 
courses  consequent  on  the  new  constructional  form  of  the  land. 
Hence,  after  a  disturbance  we  may  expect  to  find  the  smaller 
streams  of  the  former  cycle  pretty  completely  destroyed,  while 
some  of  the  larger  ones  may  still  persist ;  these  would  then  be 
called  antecedent  streams  in  accordance  with  the  nomenclature 
introduced  by  Powell  (a,  153,  163-166).  A  fuller  acquaintance 
with  the  development  of  our  rivers  will  probably  give  us  ex- 
amples of  river  systems  of  all  degrees  of  extinction  or  persist- 
ence at  times  of  disturbance. 

Since  Powell  introduced  the  idea  of  antecedent  valleys  and 
Tietze,  Medlicott,  and  others  showed  the  validity  of  the  explana- 
tion in  other  regions  than  the  one  for  which  it  was  first  proposed, 
it  has  found  much  acceptance.  Lowl's  objection  to  it  does  not 
seem  to  me  to  be  nearly  so  well  founded  as  his  suggestion  of  an 
additional  method  of  river  development  by  means  of  backward 
headwater  erosion  and  subsequent  capture  of  other  streams,  as 
already  described.  And  yet  I  cannot  help  thinking  that  the  ex- 
planation of  transverse  valleys  as  antecedent  courses  savors  of 
the  Gordian  method  of  explaining  a  difficult  matter.  The  case 
of  the  Green  river,  to  which  Powell  first  gave  this  explanation, 
seems  well  supported  ;  the  examples  given  by  Medlicott  in  the 
Himalayas  are  as  good  ;  but  still  it  does  not  seem  advisable  to 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    445 

explain  all  transverse  streams  in  this  way,  merely  because  they 
are  transverse.  Perhaps  one  reason  why  the  explanation  has 
become  so  popular  is  that  it  furnishes  an  escape  from  the  old 
catastrophic  idea  that  fractures  control  the  location  of  valleys, 
and  is  at  the  same  time  fully  accordant  with  the  ideas  of  the 
uniformitarian  school  that  have  become  current  in  this  half  of 
our  century.  But  when  it  is  remembered  that  most  of  the 
streams  of  a  region  are  extinguished  at  the  time  of  mountain 
growth,  that  only  a  few  of  the  larger  ones  can  survive,  and  that 
there  are  other  ways  in  which  transverse  streams  may  originate 
(Hilber),  it  is  evident  that  the  possibility  of  any  given  transverse 
stream  being  antecedent  must  be  regarded  only  as  a  suggestion, 
until  some  independent  evidence  is  introduced  in  its  favor.  This 
may  be  difficult  to  find,  but  it  certainly  must  be  searched  for; 
if  not  then  forthcoming,  the  best  conclusion  may  be  to  leave  the 
case  open  until  the  evidence  appears.  Certainly,  if  we  find  a 
river  course  that  is  accordant  in  its  location  with  the  complicated 
results  of  other  methods  of  origin,  then  the  burden  of  proof  may 
be  said  to  lie  with  those  who  would  maintain  that  an  antecedent 
origin  would  locate  the  river  in  so  specialized  a  manner.  Even 
if  a  river  persist  for  a  time  in  an  antecedent  course,  this  may 
not  prevent  its  being  afterwards  affected  by  the  various  adjust- 
ments and  revivals  that  have  been  explained  above ;  rivers  so 
distinctly  antecedent  as  the  Green  and  the  Sutlej  may  hereafter 
be  more  or  less  affected  by  processes  of  adjustment,  which  they 
are  not  yet  old  enough  to  experience.  Hence,  in  mountains  as 
old  as  the  Appalachians  the  courses  of  the  present  rivers  need 
not  coincide  with  the  location  of  the  pre-Permian  rivers,  even  if 
the  latter  persisted  in  their  courses  through  the  growth  of  the 
Permian  folding  ;  subsequent  elevations  and  adjustments  to  hard 
beds,  at  first  buried  and  unseen,  may  have  greatly  displaced 
them,  in  accordance  with  Lowl's  principle. 

When  the  deeper  channeling  of  a  stream  discovers  an  uncon- 
formable  subjacent  terrane,  the  streams  persist,  at  least  for  a 
time,  in  the  courses  that  were  determined  in  the  overlying  mass  ; 
they  are  then  called  superimposed  (Powell),  inherited  (Shaler), 
or  epigenetic  (Richthofen).  Such  streams  are  particularly  liable 
to  readjustment  by  transfer  of  channels  from  courses  that  lead 


446  PHYSIOGRAPHIC  ESSAYS 

them  over  hard  beds  to  others  on  which  the  hard  beds  are 
avoided  ;  for  the  first  choice  of  channels,  when  the  unconform- 
able  cover  was  still  present,  was  made  without  any  knowledge 
of  the  buried  rock  structure  or  of  the  difficulties  in  which  the 
streams  would  be  involved  when  they  encountered  it.  The  ex- 
amples of  falls  produced  when  streams  terrace  their  flood  plains 
and  run  on  buried  spurs  has  already  been  referred  to  as  super- 
imposed ;  and  the  rivers  of  Minnesota  now  disclosing  half -buried 
ledges  here  and  there  may  be  instanced  as  illustrating  the  transi- 
tion stage  between  simple  consequent  courses,  determined  by  the 
form  of  the  drift  sheet  on  which  their  flow  began,  and  the  fully 
inconsequent  courses  that  will  be  developed  there  in  the  future. 

Simple,  Compound,  Composite,  and  Complex  Rivers.  We  have 
thus  far  considered  an  ideal  river.  It  now  seems  advisable  to 
introduce  a  few  terms  with  which  to  indicate  concisely  certain 
well-marked  peculiarities  in  the  history  of  actual  rivers. 

An  original  river  has  already  been  defined  as  one  which  first 
takes  possession  of  a  land  area,  or  which  replaces  a  completely 
extinguished  river  on  a  surface  of  rapid  deformation. 

A  river  may  be  simple  if  its  drainage  area  is  of  practically 
one  kind  of  structure  and  of  one  age,  like  the  rivers  of  southern 
New  Jersey.  Such  rivers  are  generally  small.  It  may  be  com- 
posite when  drainage  areas  of  different  structure  are  included 
in  the  basin  of  a  single  stream.  This  is  the  usual  case. 

A  compound  river  is  one  which  is  of  different  ages  in  its  differ- 
ent parts,  as  certain  rivers  of  North  Carolina  which  have  old 
headwaters  rising  in  the  mountains  and  young,  lower  courses 
traversing  the  coastal  plain. 

A  river  is  complex  when  it  has  entered  a  second  or  later  cycle 
of  development ;  the  headwaters  of  a  compound  river  are  there- 
fore complex,  while  the  lower  course  may  be  simple  in  its  first 
cycle.  The  degree  of  complexity  measures  the  number  of  cycles 
that  the  river  has  entered. 

When  the  study  of  rivers  is  thus  attempted,  its  necessary 
complications  may  at  first  seem  so  great  as  to  render  it  of  no 
value  ;  but  in  answer  to  this  I  believe  that  it  may  be  fairly  urged 
that,  although  complicated,  the  results  are  true  to  nature,  and  if 
so,  we  can  have  no  ground  of  complaint  against  them.  Moreover, 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    447 

while  it  is  desirable  to  reduce  the  study  of  the  development  of 
rivers  to  its  simplest  form  in  order  to  make  it  available  for  instruc- 
tion and  investigation,  it  must  be  remembered  that  this  cannot 
be  done  by  neglecting  to  investigate  the  whole  truth  in  the  hope 
of  avoiding  too  great  complexity,  but  that  simplicity  can  be 
reached  safely  only  through  fullness  of  knowledge,  if  at  all. 

It  is  with  these  points  in  mind  that  I  have  attempted  to  de- 
cipher the  history  of  the  rivers  of  Pennsylvania.  We  find  in 
the  Susquehanna,  which  drains  a  great  area  in  the  central  part 
of  the  state,  an  example  of  a  river  which  is  at  once  composite, 
compound,  and  highly  complex.  It  drains  districts  of  diverse 
structure ;  it  traverses  districts  of  different  ages ;  and  it  is  at 
present  in  its  fourth  or  fifth  degree  of  complexity,  its  fourth  or 
fifth  cycle  of  development  at  least.  In  unraveling  its  history 
and  searching  out  the  earlier  courses  of  streams  which  may  have 
long  since  been  abandoned  in  the  processes  of  mature  adjust- 
ment, it  will  be  seen  that  the  size  of  the  present  streams  is  not 
always  a  measure  of  their  previous  importance,  and  to  this  we 
may  ascribe  the  difficulty  that  attends  the  attempt  to  decipher  a 
river's  history  from  general  maps  of  its  stream  lines.  Nothing 
but  a  detailed  examination  of  geological  structure  and  history 
suffices  to  detect  facts  and  conditions  that  are  essential  to  the 
understanding  of  the  result. 

If  the  postulates  that  I  shall  use  seem  unsound  and  the  argu- 
ments seem  overdrawn,  error  may  at  least  be  avoided  by  not 
holding  fast  to  the  conclusions  that  are  presented,  for  they  are 
presented  only  tentatively.  I  do  not  feel  by  any  means  absolutely 
persuaded  of  the  correctness  of  the  results,  but  at  the  same  time 
deem  them  worth  giving  out  for  discussion.  The  whole  investi- 
gation was  undertaken  as  an  experiment  to  see  where  it  might 
lead,  and  with  the  hope  that  it  might  lead  at  least  to  a  serious 
study  of  our  river  problems. 

IV.    THE  DEVELOPMENT  OF  THE  RIVERS  OF  PENNSYLVANIA 

Means  of  Distinguishing  between  Antecedent  and  Adjusted 
Consequent  Rivers.  The  outline  of  the  geological  history  of 
Pennsylvania  given  above  affords  means  of  dividing  the  long 


448  PHYSIOGRAPHIC  ESSAYS 

progress  of  the  development  of  our  rivers  into  the  several  cycles 
which  make  up  their  complete  life.  We  must  go  far  back  into 
the  past  and  imagine  ancient  streams  flowing  down  from  the 
Archaean  land  towards  the  Paleozoic  sea,  gaining  length  by  ad- 
dition to  their  lower  portions  as  the  land  grew  with  the  building 
on  of  successive  mountain  ranges ;  for  example,  if  there  were  a 
Cambro-Silurian  deformation,  a  continuation  of  the  Green  moun- 
tains into  Pennsylvania,  we  suppose  that  the  preexistent  streams 
must  in  some  manner  have  found  their  way  westward  to  the  new 
coast  line  ;  and  from  the  date  of  this  mountain  growth  it  is  ap- 
parent that  any  streams  then  born  must  have  advanced  far  in 
their  history  before  the  greater  Appalachian  disturbance  began. 
At  the  beginning  of  the  latter,  as  of  the  former,  there  must  have 
been  streams  running  from  the  land  into  the  sea,  and  at  times 
of  temporary  elevation  of  the  broad  sand  flats  of  the  coal  meas- 
ures such  streams  must  have  had  considerable  additions  to  their 
lower  length,  rising  in  long-growing  Archaean  highlands  or  moun- 
tains, snow-capped  and  drained  by  glaciers  for  all  we  can  say  to 
the  contrary,  descending  across  the  Green  mountain  belt,  by 
that  time  worn  to  moderate  relief  in  the  far-advanced  stage  of 
its  topographical  development,  and  finally  flowing  across  the  coal- 
measure  lowlands  of  recent  appearance.  It  was  across  the  lower 
courses  of  such  rivers  that  the  Appalachian  folds  were  formed, 
and  the  first  step  in  our  problem  consists  in  deciding,  if  possible, 
whether  the  streams  held  their  courses  after  the  antecedent 
fashion,  or  whether  they  were  thrown  into  new  courses  by  the 
growing  folds,  so  that  a  new  drainage  system  would  be  formed. 
Possibly  both  conditions  prevailed,  the  larger  streams  holding 
their  courses  little  disturbed,  and  the  smaller  ones  disappearing, 
to  be  replaced  by  others  as  the  slopes  of  the  growing  surface 
should  demand.  It  is  not  easy  to  make  choice  in  this  matter. 
To  decide  that  the  larger  streams  persisted  and  are  still  to  be 
seen  in  the  greater  rivers  of  to-day,  only  reversed  in  direction  of 
flow,  is  certainly  a  simple  niethod  of  treating  the  problem,  but 
unless  some  independent  reasons  are  found  for  this  choice,  it 
savors  of  assumption.  Moreover,  it  is  difficult  to  believe  that 
any  streams,  even  if  antecedent  and  more  or  less  persistent  for 
a  time  during  the  mountain  growth,  could  preserve  till  now  their 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    449 

pre-Appalachian  courses  through  all  the  varying  conditions  pre- 
sented by  the  alternations  of  hard  and  soft  rocks  through  which 
they  have  had  to  cut,  and  at  all  the  different  altitudes  above 
base-level  in  which  they  have  stood.  A  better  means  of  decid- 
ing the  question  will  be  to  admit  provisionally  the  occurrence  of 
a  completely  original  system  of  consequent  drainage,  located  in 
perfect  accord  with  the  slopes  of  the  growing  mountains ;  to 
study  out  the  changes  of  stream  courses  that  would  result  from 
later  disturbances  and  from  the  mutual  adjustments  of  the  sev- 
eral members  of  such  a  system  in  the  different  cycles  of  its  his- 
tory ;  and  finally  to  compare  the  courses  thus  deduced  with  those 
now  seen.  If  there  be  no  accord,  either  the  method  is  wrong  or 
the  streams  are  not  consequent  but  of  some  other  origin,  such  as 
antecedent ;  if  the  accord  between  deduction  and  fact  be  well 
marked,  varying  only  where  no  definite  location  can  be  given  to 
the  deduced  streams,  but  agreeing  where  they  can  be  located 
more  precisely,  then  it  seems  to  me  that  the  best  conclusion  is 
distinctly  in  favor  of  the  correctness  of  the  deductions.  ^For  it  is 
not  likely,  even  if  it  be  possible,  that  antecedent  streams  should 
have  accidentally  taken,  before  the  mountains  were  formed,  just 
such  locations  as  would  have  resulted  from  the  subsequent  growth 
of  the  mountains  and  from  the  complex  changes  in  the  initial 
river  courses  due  to  later  adjustments.  I  shall  therefore  follow 
the  deductive  method  thus  indicated  and  attempt  to  trace  out 
the  history  of  a  completely  original,  consequent  system  of  drain- 
age accordant  with  the  growth  of  the  central  mountain  district. 

In  doing  this,  it  is  first  necessary  to  restore  the  constructional 
topography  of  the  region ;  that  is,  the  form  that  the  surface 
would  have  had  if  no  erosion  had  accompanied  the  deformation. 
This  involves  certain  postulates  which  must  be  clearly  conceived 
if  any  measure  of  confidence  is-  to  be  gained  in  the  results  based 
upon  them. 

Postulates  of  the  Argument.  In  the  first  place,  I  assume  an 
essential  constancy  in  the  thickness  of  the  Paleozoic  sediments 
over  the  entire  area  in  question.  This  is  warranted  here  because 
the  known  variations  of  thickness  are  relatively  of  a  second 
order,  and  will  not  affect  the  distribution  of  high  and  low  ground 
as  produced  by  the  intense  Permian  folding.  The  reasons  for 


450  PHYSIOGRAPHIC  ESSAYS 

maintaining  that  the  whole  series  had  a  considerable  extension 
southeast  of  the  present  margin  of  the  Medina  sandstone  have 
already  been  presented. 

In  the  second  place,  I  shall  assume  that  the  dips  and  folds  of 
the  beds  now  exposed  at  the  surface  of  the  ground  may  be  pro- 
jected upwards  into  the  air  in  order  to  restore  the  form  of  the 
eroded  beds.  This  is  certainly  inadmissible  in  detail,  for  it  can- 
not be  assumed  that  the  folded  slates  and  limestones  of  the 
Nittany  valley,  for  instance,  give  any  close  indication  of  the  form 
that  the  coal  measures  would  have  taken,  had  they  extended 
over  this  district,  unworn.  But,  in  a  general  way,  the  Nittany 
massif  was  a  complex  arch  in  the  coal  measures  as  well  as  in  the 
Cambrian  beds  ;  for  our  purpose  and  in  view  of  the  moderate 
relief  of  the  existing  topography  it  suffices  to  say  that  wherever 
the  lower  rocks  are  now  revealed  in  anticlinal  structure,  there 
was  a  great  upfolding  and  elevation  of  the  original  surface ;  and 
wherever  the  higher  rocks  are  still  preserved,  there  was  a  rela- 
tively small  elevation. 

In  the  third  place,  I  assume  that  by  reconstructing  from  the 
completed  folds  the  form  which  the  country  would  have  had  if 
unworn,  we  gain  a  sufficiently  definite  picture  of  the  form  through 
which  it  actually  passed  at  the  time  of  initial  and  progressive 
folding.  The  difference  between  the  form  of  the  folds  com- 
pletely restored  and  the  form  that  the  surface  actually  reached 
is  rather  one  of  degree  than  of  kind ;  the  two  must  correspond 
in  the  general  distribution  of  high  and  low  ground,  and  this  is 
the  chief  consideration  in  our  problem.  When  we  remember 
how  accurately  water  finds  its  level,  it  will  be  clearer  that  what 
is  needed  in  the  discussion  is  the  location  of  the  regions  that 
were  relatively  raised  and  lowered,  as  we  shall  then  have  marked 
out  the  general  course  of  the  consequent  water  ways  and  the 
trend  of  the  intervening  constructional  ridges. 

Accepting  these  postulates,  it  may  be  said,  in  brief,  that  the 
outlines  of  the  formations  as  at  present  exposed  are  in  effect  so 
many  contour  lines  of  the  old  constructional  surface,  on  which 
the  Permian  rivers  took  their  consequent  courses.  Where  the 
Trenton  limestone  is  now  seen,  the  greatest  amount  of  overlying 
strata  must  have  been  removed  ;  hence  the  outline  of  the  Trenton 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    451 

formation  is  our  highest  contour  line.  Where  the  Helderberg 
limestone  appears,  there  has  been  a  less  amount  of  material 
removed  ;  hence  the  Helderberg  outcrop  is  a  contour  of  less  ele- 
vation. Where  the  coal  beds  are  still  preserved,  there  has  been 
least  wasting,  and  these  beds  therefore  mark  the  lowest  contour 
of  the  early  surface.  It  is  manifest  that  this  method  assumes 
that  the  present  outcrops  are  on  a  level  surface  ;  this  is  not  true, 
for  the  ridges  through  the  state  rise  a  thousand  feet  more  or 
less  over  the  intervening  valley  lowlands,  and  yet  the  existing 
relief  does  not  count  for  much  in  discussing  the  enormous  relief 
of  the  Permian  surface  that  must  have  been  measured  in  tens  of 
thousands  of  feet  at  the  time  of  its  greatest  strength. 

Constructional  Permian  Topography  and  Consequent  Drainage. 
A  rough  restoration  of  the  early  constructional  topography  is 
given  in  Fig.  31  for  the  central  part  of  the  state,  the  closest 
shading  being  the  area  of  the  Trenton  limestone,  indicating  the 
highest  ground,  or,  better,  the  places  of  greatest  elevation,  while 
the  Carboniferous  area  is  unshaded,  indicating  the  early  low- 
lands. The  prevalence  of  northeast  and  southwest  trends  was 
then  even  more  pronounced  than  now.  Several  of  the  stronger 
elements  of  form  deserve  names  for  convenient  reference.  Thus 
we  have  the  great  Kittatinny,  or  Cumberland  highland,  CC,  on 
the  southeast,  backed  by  the  older  mountains  of  Cambrian  and 
Archaean  rocks,  falling  by  the  Kittatinny  slope  to  the  synclinal 
lowland  troughs  of  the  central  district.  In  this  lower  ground 
lay  the  synclinal  troughs  of  the  eastern  coal  regions,  and  the 
more  local  Broad  Top  basin,  BT,  on  the  southwest,  then  better 
than  now  deserving  the  name  of  basins.  Beyond  the  corrugated 
area  that  connected  the  coal  basins  rose  the  great  Nittany 
highland,  N,  and  its  southwest  extension  in  the  Bedford  range, 
with  the  less  conspicuous  Kishicoquilas  highland,  A',  in  the 
foreground.  Beyond  all  stretched  the  great  Allegheny  low- 
land plains.  The  names  thus  suggested  are  compounded  of 
the  local  names  of  to-day  and  the  morphological  names  of 
Permian  time. 

What  would  be  the  drainage  of  such  a  country  ?  Deductively 
we  are  led  to  believe  that  it  consisted  of  numerous  streams,  as 
marked  in  full  lines  on  the  figure,  following  synclinal  axes  until 


452 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA   453 

some  master  streams  led  them  across  the  intervening  anticlinal 
ridges  at  the  lowest  points  of  their  crests  and  away  into  the 
open  country  to  the  northwest.  All  the  inclosed  basins  would 
hold  lakes,  overflowing  at  the  lowest  part  of  the  rim.  The  gen- 
eral discharge  of  the  whole  system  would  be  to  the  northwest. 
Here  again  we  must  resort  to  special  names  for  the  easy  indica- 
tion of  these  well-marked  features  of  the  ancient  and  now  appar- 
ently lost  drainage  system.  The  master  stream  of  the  region  is 
the  great  Anthracite  river,  carrying  the  overflow  of  the  Anthra- 
cite lakes  off  to  the  northwest,  and  there  perhaps  turning  along 
one  of  the  faintly  marked  synclines  of  the  plateau  and  joining 
the  original  Ohio,  which  was  thus  confirmed  in  its  previous  loca- 
tion across  the  Carboniferous  marshes.  The  synclinal  streams 
that  entered  the  Anthracite  lakes  from  the  southwest  (Fig.  31) 
may  be  named,  beginning  on  the  south,  the  Swatara  (S),  the 
Wiconisco  (Wo),  the  Tuscarora-Mahanoy  (M),  the  Juniata-Cata- 
wissa  (C),  and  the  Wyoming  (Wy).  One  of  these,  probably  the 
fourth,  led  the  overflow  from  the  Broad  Top  lake  into  the  Cata- 
wissa  lake  on  the  middle  Anthracite  river.  The  Nittany  high- 
land formed  a  strong  divide  between  the  central  and  northwestern 
rivers,  and  on  its  outer  slope  there  must  have  been  streams  de- 
scending to  the  Allegheny  lowlands  ;  and  some  of  these  may  be 
regarded  as  the  lower  courses  of  Carboniferous  rivers  that  once 
rose  in  the  Archaean  mountains,  now  beheaded  by  the  growth  of 
mountain  ranges  across  their  middle.  ^ 

The  Jura  Mountains  Homologous  with  the  Permian  Alle- 
ghenies.  However  willing  one  may  be  to  grant  the  former  exist- 
ence of  such  a  drainage  system  as  the  above,  an  example  of  a 
similar  one  still  in  existence  would  be  acceptable  as  a  witness 
to  the  possibilities  of  the  past.  Therefore  we  turn  for  a  moment 
to  the  Jura  mountains,  always  compared  to  the  Appalachians  on 
account  of  the  regular  series  of  folds  by  which  the  two  are  char- 
acterized. But  while  the  initial  topography  is  long  lost  in  our 
old  mountains,  it  is  still  clearly  perceptible  in  the  young  Jura, 
where  the  anticlines  are  still  ridges  and  the  longitudinal  streams 
still  follow  the  synclinal  troughs  ;  while  the  transverse  streams 
cross  from  one  synclinal  valley  to  another  at  points  where  the 
intervening  anticlinal  arches  are  lowest.  We  could  hardly  ask 


454  PHYSIOGRAPHIC  ESSAYS 

for  better  illustration  of  the  deductive  drainage  system  of  our 
early  Appalachians  than  is  here  presented. 

Development  and  Adjustment  of  the  Permian  Drainage.  The 
problem  is  now  before  us.  Can  the  normal  sequence  of  changes 
in  the  regular  course  of  river  development,  aided  by  the  post- 
Permian  deformations  and  elevations,  evolve  the  existing  rivers 
out  of  the  ancient  ones  ? 

In  order  to  note  the  degree  of  comparison  that  exists  be- 
tween the  two,  several  of  the  larger  rivers  of  to-day  are  dotted 
on  the  figure.  The  points  of  agreement  are  indeed  few  and  small. 
Perhaps  the  most  important  ones  are  that  the  Broad  Top  region 
is  drained  by  a  stream,  the  Juniata,  which  for  a  short  distance 
follows  near  the  course  predicted  for  it ;  and  that  the  Nittany 
district,  then  a  highland,  is  still  a  well-marked  divide,  although 
now  a  lowland.  But  there  is  no  Anthracite  river,  and  the  region 
of  the  ancient  coal-basin  lakes  is  now  avoided  by  large  streams ; 
conversely,  a  great  river  —  the  Susquehanna  —  appears  where 
no  consequent  river  ran  in  Permian  time,  and  the  early  synclinal 
streams  frequently  turn  from  the  structural  troughs  to  valleys 
located  on  the  structural  arches. 

Lateral  Water  Gaps  near  the  Apex  of  Synclinal  Ridges.  One 
of  the  most  frequent  discrepancies  between  the  hypothetical 
and  actual  streams  is  that  the  latter  never  follow  the  axis  of  a 
descending  syncline  along  its  whole  length,  as  the  original 
streams  must  have  done,  but  depart  for  a  time  from  the  axis 
and  then  return  to  it,  notching  the  ridge  formed  on  any  hard 
bed  at  the  side,  instead  of  at  the  apex,  of  its  curve  across  the 
axis  of  the  syncline.  There  is  not  a  single  case  in  the  state  of  a 
stream  cutting  a  gap  at  the  apex  of  such  a  synclinal  curve,  but 
there  are  perhaps  hundreds  of  cases  where  the  streams  notch 
the  curve  to  one  side  of  the  apex.  This,  however,  is  precisely 
the  arrangement  attained  by  spontaneous  adjustment  from  an 
initial  axial  course,  as  indicated  in  Fig.  23.  The  gaps  may  be 
located  on  small  transverse  faults,  but  as  a  rule  they  seem  to 
have  no  such  guidance.  It  is  true  that  most  of  our  streams  now 
run  out  of  and  not  into  the  synclinal  basins,  but  a  reason  for 
this  will  be  found  later;  for  the  present  we  look  only  at  the 
location  of  the  streams,  not  at  their  direction  of  flow.  As  far  as 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    455 

this  illustration  goes,  it  gives  evidence  that  the  smaller  streams 
at  least  possess  certain  peculiarities  that  could  not  be  derived 
from  persistence  in  a  previous  accidental  location,  but  which 
would  necessarily  be  derived  from  a  process  of  adjustment  fol- 
lowing the  original  establishment  of  strictly  consequent  streams. 
Hence  the  hypothesis  that  these  smaller  streams  were  long  ago 
consequent  on  the  Permian  folding  receives  confirmation ;  but 
this  says  nothing  as  to  the  origin  of  the  larger  rivers,  which 
might  at  the  same  time  be  antecedent. 

Departure  of  the  Juniata  from  the  Juniata-Catawissa  Syncline. 
It  may  next  be  noted  that  the  drainage  of  the  Broad  Top  region 
does  not  follow  a  single  syncline  to  the  Anthracite  region,  as  it 
should  have  in  the  initial  stage  of  the  consequent  Permian  drain- 
age, but  soon  turns  aside  from  the  syncline  in  which  it  starts 
and  runs  across  country  to  the  Susquehanna.x  It  is  true  that  in 
its  upper  course  the  Juniata  departs  from  the  Broad  Top  region 
by  one  of  the  two  synclines  that  were  indicated  as  the  probable 
line  of  discharge  of  the  ancient  Broad  Top  lake  in  our  restoration 
of  the  constructional  topography  of  the  state ;  there  does  not 
appear  to  be  any  significant  difference  between  the  summit 
altitudes  of  the  Tuscarora-Mahanoy  and  the  Juniata-Catawissa 
synclinal  axes,  and  hence  the  choice  must  have  been  made  for 
reasons  that  cannot  be  detected ;  or  it  may  be  that  the  syncline 
lying  more  to  the  northwest  was  raised  last,  and  for  this  reason 
was  taken  as  the  line  of  overflow.  The  beginning  of  the  river 
is  therefore  not  discordant  with  the  hypothesis  of  consequent 
drainage,  but  the  southward  departure  from  the  Catawissa  syn- 
cline at  Lewistown  remains  to  be  explained.  It  seems  to  me 
that  some  reason  for  the  departure  may  be  found  by  likening  it 
to  the  case  already  given  in  Figs.  26-28.  The  several  synclines 
with  which  the  Juniata  is  concerned  have  precisely  the  relative 
attitudes  that  are  there  discussed.  The  Juniata-Catawissa  syn- 
cline has  parallel  sides  for  many  miles  about  its  middle,  and 
•hence  must  have  long  maintained  the  initial  Juniata  well  above 
base-level  over  all  this  distance ;  the  progress  of  cutting  down 
a  channel  through  all  the  hard  Carboniferous  sandstones  for  so 
great  a  distance  along  the  axis  must  have  been  exceedingly  slow. 
But  the  synclines  next  south,  the  Tuscarora-Mahanoy  and  the 


456  PHYSIOGRAPHIC   ESSAYS 

Wiconisco,  plunge  to  the  northeast  more  rapidly,  as  the  rapid 
divergence  of  their  margins  demonstrates,  and  must  for  this 
reason  have  carried  the  hard  sandstones  below  base-level  in  a 
shorter  distance  and  on  a  steeper  slope  than  in  the  Catawissa 
syncline.  The  further  southwestward  extension  of  the  Pocono 
sandstone  ridges  in  the  southern  than  in  the  northern  syncline 
gives  further  illustration  of  this  peculiarity  of  form.  Lateral 
capture  of  the  Juniata  by  a  branch  of  the  initial  Tuscarora,  and 
of  the  latter  by  a  branch  of  the  Wiconisco,  therefore  seems  pos- 
sible, and  the  accordance  of  the  facts  with  so  highly  specialized 
an  arrangement  is  certainly  again  indicative  of  the  correctness 
of  the  hypothesis  of  consequent  drainage,  and  this  time  in  a 
larger  stream  than  before.  At  first  sight  it  appears  that  an 
easier  lateral  capture  might  have  been  made  by  some  of  the 
streams  flowing  from  the  outer  slope  of  the  Nittany  highland  ; 
this  becomes  improbable  when  it  is  perceived  that  the  heavy 
Medina  sandstone  would  here  have  to  be  worn  through,  as  well  as 
the  repeated  arches  of  the  Carboniferous  beds  in  the  many  high 
folds  of  the  Seven  mountains.  Again,  as  far  as  present  appear- 
ances go,  we  can  give  no  sufficient  reason  to  explain  why  posses- 
sion of  the  headwaters  of  the  Juniata  was  not  gained  by  some 
subsequent  stream  of  its  own,  such  as  G  (Fig.  28),  instead  of  by 
a  side  stream  of  the  river  in  the  neighboring  syncline  ;  but  it  may 
be  admitted,  on  the  other  hand,  that  as  far  as  we  can  estimate 
the  chances  for  conquest,  there  was  nothing  distinctly  in  favor  of 
one  or  the  other  of  the  side  streams  concerned  ;  and  as  long  as 
the  problem  is  solved  indifferently  in  favor  of  one  or  the  other, 
we  may  accept  the  lead  of  the  facts  and  say  that  some  control 
not  now  apparent  determined  that  the  diversion  should  be,  as 
drawn,  through  D  and  not  through  G.  The  detailed  location  of 
the  Juniata  in  its  middle  course  below  Lewistown  will  be  con- 
sidered in  a  later  section. 

Avoidance  of  the  Broqd  Top  Basin  by  the  Juniata  Headwaters, 
Another  highly  characteristic  change  that  the  Juniata  has  suf- 
fered is  revealed  by  examining  the  adjustments  that  would  have 
taken  place  in  the  general  topography  of  the  Broad  Top  district 
during  the  Perm-Triassic  cycle  of  erosion.  When  the  basin  B7 
(Fig.  32)  was  first  outlined,  centripetal  streams  descended  its 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    457 

slopes  from  all  sides,  and  their  waters  accumulated  as  a  lake  in 
the  center,  overflowing  to  the  east  into  the  subordinate  basin  A, 
in  the  Juniata  syncline  alongside  of  the  larger  basin,  and  thence 
escaping  northeast.  In  due  time  the  breaching  of  the  slopes 
opened  the  softer  Devonian  rocks  beneath,  and  peripheral  low- 
lands were  opened  on  them.XThe  process  by  which  the  Juniata 
departed  from  its  original  axial  location,/ (Fig.  32),  to  a  parallel 
course  on  the  southeastern  side  of  the  syncline,  J  (Fig.  33),  has 
been  described  (Fig.  28).  The  subsequent  changes  are  manifest. 
Some  lateral  branch  of  the  Juniata,  like  N(Fig.  33),  would  work 
its  way  around  the  northern  end  of  the  Broad  Top  canoe  on 


FIG.  33 


FIG.  34 


the  soft,  underlying  rocks  and  capture  the  axial  stream,  C,  that 
came  from  the  depression  between  Nittany  and  Kishicoquillas 
highlands ;  thus  reenforced,  capture  would  be  made  of  a  radial 
stream  from  the  west,  Tn,  the  existing  Tyrone  branch  of  the 
Juniata ;  in  a  later  stage  the  other  streams  of  the  western  side 
of  the  basin  would  be  acquired,  their  divertor  constituting  the 
Little  Juniata  of  to-day;  and  the  end  would  be  when  the  original 
Juniata,  A  (Fig.  32),  that  once  issued  from  the  subordinate  syn- 
clinal as  a  large  stream,  had  lost  all  its  western  tributaries,  and 
was  but  a  shrunken,  beheaded  remnant  of  a  river,  now  seen  in 
Aughwick  creek,  A  (Fig.  34).  In  the  meantime  the  former  lake 
basin  was  fast  becoming  a  synclinal  mountain  of  diminishing 
perimeter.  The  only  really  mysterious  courses  of  the  present 
streams  are  where  the  Little  Juniata  runs  in  and  out  of  the 


458  PHYSIOGRAPHIC   ESSAYS 

western  border  of  the  Broad  Top  synclinal,  and  where  the  Franks- 
town  (FT)  branch  of  the  Juniata  maintains  its  independent  gap 
across  Tussey's  mountain  (Medina),  although  diverted  to  the 
Tyrone,  or  main  Juniata  (Tn),  by  Warrior's  ridge  (Oriskany)  just 
below.  At  the  time  of  the  early  predatory  growth  of  the  initial 
divertor  Nt  its  course  lay  by  the  very  conditions  of  its  growth 
on  only  the  weakest  rocks  ,*  but  after  this  little  stream  had 
grown  to  a  good-sized  river,  further  rising  of  the  land,  probably 
in  the  time  of  the  Jurassic  elevation,  allowed  the  river  to  sink 
its  channel  to  a  greater  depth,  and  in  doing  so  it  encountered 
the  hard  Medina  anticline  of  Jack's  mountain ;  here  it  has  since 
persisted  because,  as  we  may  suppose,  there  has  been  no  stream 
able  to  divert  the  course  of  so  large  a  river  from  its  crossing  of 
a  single  hard  anticlinal. 

The  doubt  that  one  must  feel  as  to  the  possibility  of  the  proc- 
esses just  outlined  arises,  if  I  may  gauge  it  by  my  own  feeling, 
rather  from  incredulity  than  from  direct  objections.  It  seems 
incredible  that  the  waste  of  the  valley  slopes  should  allow  the 
backward  growth  of  JV  at  such  a  rate  as  to  enable  it  to  capture 
the  heads  of  C,  Tn,  F,  and  so  on,  before  they  had  cut  their  beds 
down  close  enough  to  the  base-level  of  the  time  to  be  safe  from 
capture.  But  it  is  difficult  to  urge  explicit  objections  against 
the  process  or  to  show  its  quantitative  insufficiency.  It  must  be 
remembered  that  when  these  adjustments  were  going  on,  the 
region  was  one  of  great  altitude,  its  rocks  then  had  the  same 
strong  contrasts  of  strength  and  weakness  that  are  so  apparent 
in  the  present  relief  of  the  surface,  and  the  streams  concerned 
were  of  moderate  size  ;  less  than  now,  for  at  the  time  the  Ty- 
rone, Frankstown,  and  Bedford  head  branches  of  the  Juniata 
had  not  acquired  drainage  west  of  the  great  Nittany-Bedford 
anticlinal  axis,  but  were  supplied  only  by  the  rainfall  on  its 
eastern  slope,  and  all  these  conditions  conspired  to  favor  the  ad- 
justment. Finally,  while  apparently  extraordinary  and  difficult 
of  demonstration,  the  explanation  if  applicable  at  all  certainly 
gives  rational  correlation  to  a  number  of  peculiar  and  special 
stream  courses  in  the  upper  Juniata  district  that  are  meaningless 
under  any  other  theory  that  has  come  to  my  notice.  It  is  chiefly 
for  this  reason  that  I  am  inclined  to  accept  the  explanation. 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    459 

Reversal  of  Larger  Rivers  to  Southeast  Courses.  Our  large 
rivers  at  present  flow  to  the  southeast,  not  to  the  northwest. 
It  is  difficult  to  find  any  precise  date  for  this  reversal  of  flow 
from  the  initial  hypothetical  direction,  but  it  may  be  suggested 
that  it  occurred  about  the  time  of  the  Triassic  depression  of  the 
Newark  belt.  We  have  been  persuaded  that  much  time  elapsed 
between  the  Permian  folding  and  the  Newark  deposition,  even 
under  the  most  liberal  allowance  for  pre-Permian  erosion  in  the 
Newark  belt ;  hence  when  the  depression  began,  the  rivers 
must  have  had  but  moderate  northwestward  declivity.  The 
depression  and  submergence  of  the  broad  Newark  belt  may  at 
this  time  have  broken  the  continuity  of  the  streams  that  once 
flowed  across  it.  The  headwater  streams  from  the  ancient  Ar- 
chaean country  maintained  their  courses  to  the  depression ;  the 
lower  portions  of  the  rivers  may  also  have  gone  on  as  before ; 
but  the  middle  courses  were  perhaps  turned  from  the  central 
part  of  the  state  back  to  the  Newark  belt.  No  other  cause  gives 
so  good  an  explanation  of  the  southeastward  flow  of  our  rivers 
as  this.  The  only  test  that  I  have  been  able  to  devise  for  the 
suggestion  is  one  that  is  derived  from  the  relation  that  exists 
between  the  location  of  the  Newark  belt  along  the  Atlantic 
slope  and  the  course  of  the  neighboring  transverse  rivers.  In 
Pennsylvania,  where  the  belt  reaches  somewhat  beyond  the 
northwestern  margin  of  the  crystalline  rocks  in  South  mountain, 
the  streams  are  reversed,  as  above  stated  ;  but  in  the  Carolinas, 
where  the  Newark  belt  lies  far  to  the  east  of  the  boundary  be- 
tween the  Cambrian  and  crystalline  rocks,  the  Tennessee  streams 
persevere  in  what  we  suppose  to  have  been  their  original  direc- 
tion of  flow.  This  may  be  interpreted  as  meaning  that  in  the 
latter  region  the  Newark  depression  was  not  felt  distinctly 
enough,  if  at  all,  within  the  Allegheny  belt  to  reverse  the  flow 
of  the  streams,  while  in  the  former  region  it  was  nearer  to  these 
streams  and  determined  a  change  in  their  courses.  The  original 
Anthracite  river  ran  to  the  northwest,  but  its  middle  course 
was  afterwards  turned  to  the  southeast. 

I  am  free  to  allow  that  this  has  the  appearance  of  heaping 
hypothesis  on  hypothesis  ;  but  in  no  other  way  does  the  analysis 
of  the  history  of  our  streams  seem  possible,  and  the  success  of 


460  PHYSIOGRAPHIC  ESSAYS 

the  experiment  can  be  judged  only  after  making  it.  At  the  same 
time  I  am  constrained  to  admit  that  this  is,  to  my  own  view,  the 
least  satisfactory  of  the  suggestions  here  presented.  It  may 
be  correct,  but  there  seems  to  be  no  sufficient  exclusion  of  other 
possibilities.  For  example,  it  must  not  be  overlooked  that  if 
the  Anthracite  river  ran  southeast  during  Newark  deposition, 
the  formation  of  the  Newark  northwestward  monocline  by  the 
Jurassic  tilting  would  have  had  a  tendency  to  turn  the  river  back 
again  to  its  northwest  flow.  But  as  the  drainage  of  the  region 
is  still  southeastward,  I  am  tempted  to  think  that  the  Jurassic 
tilting  was  not  here  strong  enough  to  reverse  the  flow  of  so 
strong  and  mature  a  river  as  the  Anthracite  had  by  that  time 
come  to  be  ;  and  that  the  elevation  that  accompanied  the  tilting 
was  not  so  powerful  in  reversing  the  river  to  a  northwest  course 
as  the  previous  depression  of  the  Newark  basin  had  been  in 
turning  it  to  the  southeast.  If  the  Anthracite  did  continue  to 
flow  to  the  southeast,  it  may  be  added  that  the  down-cutting  of 
its  upper  branches  was  greatly  retarded  by  the  decrease  of  slope 
in  its  lower  course  when  the  monocline  was  formed. 

The  only  other  method  of  reversing  the  original  northwestward 
flow  of  the  streams  that  I  have  imagined  is  by  capture  of  their 
headwaters  by  Atlantic  rivers.  This  seems  to  me  less  effective 
than  the  method  just  considered ;  but  they  are  not  mutually  ex- 
clusive, and  the  actual  result  may  be  the  sum  of  the  two  processes. 
The  outline  of  the  idea  is  as  follows  :  The  long-continued  supply 
of  sedimentary  material  from  the  Archaean  land  on  the  southeast 
implies  that  it  was  as  continually  elevated.  But  there  came  a 
time  when  there  is  no  record  of  further  supply  of  material,  and 
when  we  may  therefore  suppose  the  elevation  was  no  longer 
maintained.  From  that  time  onward,  the  Archaean  range  must 
have  dwindled  away,  what  with  the  encroachment  of  the  Atlantic 
on  its  eastern  shore  and  the  general  action  of  denuding  forces  on 
its  surface.  The  Newark  depression  was  an  effective  aid  to  the 
same  end,  as  has  been  stated  above,  and  for  a  moderate  distance 
westward  of  the  depressed  belt,  the  former  direction  of  the 
streams  must  certainly  have  been  reversed  ;  but  the  question 
remains  whether  this  reversal  extended  as  far  as  the  Wyoming 
basin,  and  whether  the  subsequent  formation  of  the  Newark 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    461 

monocline  did  not  undo  the  effect  of  the  Newark  depression. 
It  is  manifest  that  as  far  as  our  limited  knowledge  goes,  it  is 
impossible  to  estimate  these  matters  quantitatively,  and  hence 
the  importance  of  looking  for  additional  processes  that  may  sup- 
plement the  effect  of  the  Newark  depression  and  counteract  the 
effect  of  the  Newark  uplift  in  changing  the  course  of  the  rivers. 
Let  it  be  supposed  for  the  moment  that  at  the  end  of  the  Jurassic 
uplift  by  which  the  Newark  monocline  was  formed,  the  divide 
between  the  Ohio  and  the  Atlantic  drainage  lay  about  the  middle 
of  the  Newark  belt.  There  was  a  long,  gentle  descent  westward 
from  this  watershed  and  a  shorter  and  hence  steeper  descent 
eastward.  Under  such  conditions  the  divide  must  have  been 
pushed  westward,  and  as  long  as  the  rocks  were  so  exposed  as  to 
open  areas  of  weak  sediments  on  which  capture  by  the  Atlantic 
streams  could  go  on  with  relative  rapidity,  the  westward  migra- 
tion of  the  divide  would  be  important.  For  this  reason  it 
might  be  carried  from  the  Newark  belt  as  far  as  the  present 
Allegheny  front,  beyond  which  further  pushing  would  be  slow, 
on  account  of  the  broad  stretch  of  country  there  covered  by 
hard  horizontal  beds. 

The  end  of  this  is  that,  under  any  of  the  circumstances  here 
detailed,  there  would  be  early  in  the  Jurassic-Cretaceous  cycle 
a  distinct  tendency  to  a  westward  migration  of  the  Atlantic- 
Ohio  divide ;  it  is  the  consequences  of  this  that  have  now  to 
be  examined. 

Capture  of  the  Anthracite  Headwaters  by  the  Growing  Susque- 
hanna.  Throughout  the  Perm-Triassic  period  of  denudation,  a 
great  work  was  done  in  wearing  down  the  original  Alleghenies. 
Anticlines  of  hard  sandstones  were  breached,  and  broad  lowlands 
were  opened  on  the  softer  rocks  beneath.  Little  semblance  of 
the  early  constructional  topography  remained  when  the  period  of 
Newark  depression  was  brought  to  a  close  ;  and  all  the  while  the 
headwater  streams  of  the  region  were  gnawing  at  the  divides, 
seeking  to  develop  the  most  perfect  arrangement  of  water  ways. 
Several  adjustments  have  taken  place,  and  the  larger  streams 
have  been  reversed  in  the  direction  of  their  flow ;  but  a  more 
serious  problem  is  found  in  the  disappearance  of  the  original 
master  stream,  the  great  Anthracite  river,  which  must  have  at 


462  PHYSIOGRAPHIC  ESSAYS 

first  led  away  the  water  from  all  the  lateral  synclinal  streams. 
Being  a  large  river,  it  could  not  have  been  easily  diverted  from 
its  course  unless  it  was  greatly  retarded  in  cutting  down  its 
channel  by  the  presence  of  many  beds  of  hard  rocks  on  its  way. 
The  following  considerations  may  perhaps  throw  some  light  on 
this  obscure  point. 

It  may  be  assumed  that  the  whole  group  of  mountains  formed 
by  the  Permian  deformation  had  been  reduced  to  a  moderate 
relief  when  the  Newark  deposition  was  stopped  by  the  Jurassic 
elevation.  The  harder  ribs  of  rocks  doubtless  remained  as  ridges 
projecting  above  the  intervening  lowlands,  but  the  strength  of 
relief  that  had  been  given  by  the  constructional  forces  had  been 
lost.  The  general  distribution  of  residual  elevations  then  remain- 
ing unsubdued  is  indicated  in  Fig.  35,  in  which  the  Crystalline, 
the  Medina,  and  the  two  Carboniferous  sandstone  ridges  are 
denoted  by  appropriate  symbols.  In  restoring  this  phase  of  the 
surface  form,  when  the  country  stood  lower  than  now,  I  have 
reduced  the  anticlines  from  their  present  outlines  and  increased 
the  synclines,  the  change  of  area  being  made  greatest  where 
the  dips  are  least,  and  hence  most  apparent  at  the  ends  of  the 
plunging  anticlines  and  synclines.  Some  of  the  Medina  anticlines 
of  Perry  and  Juniata  counties  are  not  indicated  because  they 
were  not  then  uncovered.  The  country  between  the  residual 
ridges  of  Jurassic  time  was  chiefly  Cambrian  limestone  and 
Siluro-Devonian  shales  and  soft  sandstones.  The  moderate  ridges 
developed  on  the  Oriskany  and  Chemung  sandstones  are  not 
represented.  The  drainage  of  this  stage  retained  the  original 
courses  of  the  streams,  except  for  the  adjustments  that  have 
been  described,  but  the  great  Anthracite  river  is  drawn  as  if  it 
had  been  controlled  by  the  Newark  depression  and  reversed  in 
the  direction  of  its  flow,  so  that  its  former  upper  course  on  the 
Cambrian  rocks  was  replaced  by  a  superimposed  Newark  lower 
course.  Fig.  35  therefore  represents  the  streams  for  the  most 
part  still  following  near  their  synclinal  axes,  although  departing 
from  them  where  they  have  to  enter  a  synclinal  cove-mountain 
ridge  ;  the  headwaters  of  the  Juniata  avoid  the  mass  of  hard 
sandstones  discovered  in  the  bottom  of  old  Broad  Top  lake,  and 
flow  around  them  to  the  north,  and  then  by  a  cross-country 


463 


464  PHYSIOGRAPHIC  ESSAYS 

course  to  the  Wiconisco  synclinal,  as  already  described  in  detail. 
Several  streams  come  from  the  northeast,  entering  the  Anthra- 
cite district  after  the  fashion  generalized  in  Fig.  23.  Three  of 
the  many  streams  that  were  developed  on  the  great  Kittatinny 
slope  are  located,  with  their  direction  of  flow  reversed ;  these 
are  marked  Sq,  L,  and  £>,  and  are  intended  to  represent  the 
ancestors  of  the  existing  Susquehanna,  Lehigh,  and  Delaware. 
We  have  now  to  examine  the  opportunities  offered  to  these 
small  streams  to  increase  their  drainage  areas. 

The  Jurassic  elevation,  by  which  the  Newark  deposition  was 
stopped,  restored  to  activity  all  the  streams  that  had  in  the  pre- 
vious cycle  sought  and  found  a  course  close  to  base-level.  They 
now  all  set  to  work  again  deepening  their  channels.  But  in  this 
restoration  of  lost  activity  with  reference  to  a  new  base-level, 
there  came  the  best  possible  chance  for  numerous  rearrange- 
ments of  drainage  areas  by  mutual  adjustment,  into  which  we 
must  inquire. 

I  have  already  illustrated  what  seems  to  me  to  be  the  type  of 
the  conditions  involved  at  this  time  in  Figs.  29  and  30.  The 
master  stream  A,  traversing  the  synclines,  corresponds  to  the 
reversed  Anthracite  river ;  the  lowlands  at  the  top  are  those 
that  have  been  opened  out  on  the  Siluro-Devonian  beds  of  the 
present  Susquehanna  middle  course  between  the  Pocono  and  the 
Medina  ridges.  The  small  stream  B,  that  is  gaining  drainage 
area  in  these  lowlands,  corresponds  to  the  embryo  of  the  present 
Susquehanna,  Sq  (Fig.  35),  this  having  been  itself  once  a  branch 
on  the  south  side  of  the  Swatara  synclinal  stream  (Fig.  31),  from 
which  it  was  first  turned  by  the  change  of  slope  accompanying 
the  Newark  depression ;  but  it  is  located  a  little  farther  west 
than  the  actual  Susquehanna,  so  as  to  avoid  the  two  synclinal 
cove  mountains  of  Pocono  sandstone  that  the  Susquehanna 
now  traverses,  for  reasons  to  be  stated  below.  This  stream  had 
to  cross  only  one  bed  of  hard  rock,  the  outer  wall  of  Medina 
sandstone,  between  the  broad,  inner  lowlands  of  the  relatively 
weak  Siluro-Devonian  rocks  and  the  great  valley  lowlands  on  the 
still  weaker  Cambrian  limestones.  Step  by  step  it  must  have 
pushed  its  headwater  divide  northward,  and  from  time  to  time  it 
would  have  thus  captured  a  subsequent  stream  that  crossed  the 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    465 

lowlands  eastward,  and  entered  a  Carboniferous  syncline  by  one 
of  the  lateral  gaps  already  described.  With  every  such  capture 
the  power  of  the  growing  stream  to  capture  others  was  increased. 
Fig.  29  represents  a  stage  after  the  streams  in  the  Swatara  and 
Wiconisco  synclines  (the  latter  then  having  gained  the  Juniata) 
had  been  turned  aside  on  their  way  to  the  Carboniferous  basins. 
On  the  other  hand,  the  Anthracite  river,  rising  somewhere  on 
the  plains  north  of  the  Wyoming  syncline  and  pursuing  an  irreg- 
ular course  from  one  coal  basin  to  another,  found  an  extremely 
difficult  task  in  cutting  down  its  channel  across  the  numerous 
hard  beds  of  the  Carboniferous  sandstones,  so  often  repeated  in 
the  rolling  folds  of  the  coal  fields.  It  is  also  important  to  re- 
member that  an  aid  to  other  conditions  concerned  in  the  diver- 
sion of  the  upper  Anthracite  is  found  in  the  decrease  of  slope 
that  its  lower  course  suffered  in  crossing  the  coal  fields,  if  that 
area  took  any  part  in  the  deformation  that  produced  the  Newark 
monocline,  —  whichever  theory  prove  true  in  regard  to  the  origin 
of  the  southeastward  flow  of  the  rivers, — for  loss  of  slope  in 
the  middle  course,  where  the  river  had  to  cross  many  reefs  of 
hard  sandstone,  would  have  been  very  effective  in  lengthening 
the  time  allowed  for  the  diversion  of  the  headwaters. 

The  question  is,  therefore,  whether  the  retardation  of  down- 
cutting  here  experienced  by  the  Anthracite  was  sufficient  to 
allow  the  capture  of  its  headwaters  by  the  Susquehanna.  There 
can  be  little  doubt  as  to  the  correct  quality  of  the  process,  but 
whether  it  was  quantitatively  sufficient  is  another  matter.  In 
the  absence  of  any  means  of  testing  its  sufficiency,  may  the 
result  not  be  taken  as  the  test  ?  Is  not  the  correspondence 
between  deduction  and  fact  close  enough  to  prove  the  correct- 
ness of  the  deduction  ? 

Present  Outward  Drainage  of  the  Anthracite  Basins.  The 
Lehigh,  like  the  Susquehanna,  made  an  attempt  to  capture  the 
headwaters  of  adjacent  streams,  but  failed  to  acquire  much  ter- 
ritory from  the  Anthracite  because  the  Carboniferous  sandstones, 
spread  out  between  the  two  in  a  broad  plateau  of  hard  rocks, 
across  which  the  divide  made  little  movement.  The  plateau  area 
that  its  upper  branches  drain  is,  I  think,  the  conquest  of  a  later 
cycle  of  growth.  The  Delaware  had  little  success,  except  as 


466  PHYSIOGRAPHIC  ESSAYS 

against  certain  eastern  synclinal  branches  of  the  Anthracite,  for 
the  same  reason.  The  ancestor  of  the  Swatara  of  to-day  made 
little  progress  in  extending  its  headwaters  because  its  point  of 
attack  was  against  the  repeated  Carboniferous  sandstones  in  the 
Swatara  synclinal.  One  early  stream  alone  found  a  favorable 
opportunity  for  conquest,  and  thus  grew  to  be  the  master  river, 
-  the  Susquehanna  of  to-day.  The  head  of  the  Anthracite  was 
carried  away  by  this  captor,  and  its  beheaded  lower  portion 
remains  in  our  Schuylkill.  The  Anthracite  coal  basins,  formerly 
drained  by  the  single  master  stream,  have  since  been  apportioned 
to  the  surrounding  rivers.  As  the  Siluro-Devonian  lowlands  were 
opened  around  the  coal  basins,  especially  on  the  north  and  west, 
the  streams  that  formerly  flowed  into  the  basins  were  gradually 
inverted  and  flowed  out  of  them,  as  they  still  do.  The  extent  of 
the  inversion  seems  to  be  in  a  general  way  proportionate  to  its 
opportunity.  The  most  considerable  conquests  were  made  in  the 
upper  basins,  where  theCatawissa  and  Nescopec  streams  of  to-day 
drain  many  square  miles  of  wide  valleys  opened  on  the  Mauch 
Chunk  red  shale  between  the  Pocono  and  Pottsville  sandstone 
ridges,  the  ancient  middle  waters  of  the  Anthracite  here  being 
inverted  to  the  Susquehanna  tributaries,  because  the  northern 
coal  basins  were  degraded  very  slowly  after  the  upper  Anthracite 
had  been  diverted.  The  Schuylkill  as  the  modern  representative 
of  the  Anthracite  retains  only  certain  streams  south  of  a  medial 
divide  between  Nescopec  and  Blue  mountains.  The  only  consider- 
able part  of  the  old  Anthracite  river  that  still  retains  a  course 
along  the  axis  of  a  synclinal  trough  seems  to  be  that  part  which 
follows  the  Wyoming  basin  ;  none  of  the  many  other  coal  basins 
are  now  occupied  by  the  large  stream  that  originally  followed 
them.  The  reason  for  this  is  manifestly  to  be  found  in  the  great 
depth  of  the  Wyoming  basin,  whereby  the  axial  portion  of  its 
hard  sandstones  are  even  now  below  base-level,  and  hence  have 
never  yet  acted  to  throw  the  river  from  its  axial  course.  Indeed, 
during  the  early  cycle  of  denudation,  this  basin  must  have  been 
changed  from  a  deep  lake  to  a  lacustrine  plain  by  the  accumula- 
tion in  it  of  waste  from  the  surrounding  highlands,  and  for  a 
time  the  streams  that  entered  it  may  have  flowed  in  meandering 
courses  across  the  ancient  alluvial  surface ;  the  lacustrine  and 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    467 

alluvial  condition  may  have  been  temporarily  revived  at  the  time 
of  the  Jurassic  elevation.  It  is  perhaps  as  an  inheritance  from 
a  course  thus  locally  superimposed  that 'we  may  come  to  regard 
the  deflection  of  the  river  at  Nanticoke  from  the  axis  of  the  syn- 
cline  to  a  narrow  shale  valley  on  its  northern  side  before  turning 
south  again  and  leaving  the  basin  altogether.  But  like  certain 
other  suggestions,  this  can  only  be  regarded  as  an  open  hypothe- 
sis, to  be  tested  by  some  better  method  of  river  analysis  than  we 
now  possess  ;  like  several  of  the  other  explanations  here  offered, 
it  is  presented  more  as  a  possibility  to  be  discussed  than  as  a 
conclusion  to  be  accepted. 

I  believe  that  it  was  during  the  earlier  part  of  the  great  Jura- 
Cretaceous  cycle  of  denudation  that  the  Susquehanna  thus  be- 
came the  master  stream  of  the  central  district  of  the  state.  For 
the  rest  of  the  cycle,  it  was  occupied  in  carrying  off  the  waste 
and  reducing  the  surface  to  a  well-finished  base-level  lowland 
that  characterized  the  end  of  Cretaceous  time.  From  an  active 
youth  of  conquest,  the  Susquehanna  advanced  into  an.  old  age  of 
established  boundaries  ;  and  in  later  times  its  area  of  drainage 
does  not  seem  to  have  been  greatly  altered  from  that  so  long 
ago  defined,  except  perhaps  in  the  .districts  drained  by  the 
West  and  North  Branch  headwaters. 

Homologies  of  the  Susquehanna  and  Juniata.  Looking  at  the 
change  from  the  Anthracite  to  the  Susquehanna  in  a  broad  way, 
one  may  perceive  that  it  is  an  effect  of  the  same  order  as  the 
peripheral  diversion  of  the  Broad  Top  drainage,  illustrated  in 
Figs.  32,  33,  and  34;  another  example  of  a  similar  change  is  seen 
in  the  lateral  diversion  of  the  Juniata  above  Lewistown  and  its 
rectilinear  continuation  in  Aughwick  creek,  from  their  original 
axial  location  when  they  formed  the  initial  Broad  Top  outlet. 
They  have  departed  from  the  axis  of  their  syncline  to  the  softer 
beds  on  its  southern  side  ;  FE  of  Fig.  27  has  been  diverted  to 
FD  of  Fig.  28. 

All  of  these  examples  are  truly  only  special  cases  of  the  one 
already  described,  in  which  the  Juniata  left  its  original  syncline 
for  others  to  the  south.  The  general  case  may  be  stated  in  a 
few  words.  A  stream  flowing  along  a  syncline  of  hard  beds 
(Carboniferous  sandstones)  develops  side  streams  which  breach 


468  PHYSIOGRAPHIC  ESSAYS 

the  adjacent  anticlines  and  open  lowlands  in  the  underlying 
softer  beds  (Devonian  and  Silurian).  On  these  lowlands  the 
headwaters  of  side  streams  from  other  synclines  are  encountered, 
and  a  contest  ensues  as  to  possession  of  the  drainage  territory. 
The  divides  are  pushed  away  from  those  headwaters  whose  lower 
course  leads  them  over  the  fewest  hard  barriers ;  this  conquest 
goes  on  until  the  upper  course  of  the  initial  main  stream  is 
diverted  to  a  new  and  easier  path  than  the  one  it  chose  in  its 
youth  in  obedience  to  the  first  deformation  of  the  region.  Thus 
the  Juniata  now  avoids  the  center  and  once  deepest  part  of  the 
old  Broad  Top  lake,  because  in  the  general  progress  of  erosion, 
lowlands  on  soft  Devonian  beds  were  opened  all  around  the  edge 
of  the  great  mass  of  sandstones  that  held  the  lake ;  the  original 
drainage  across  the  lake,  from  its  western  slope  to  its  outlet  just 
south  of  the  Jack's  mountain  anticline,  has  now  taken  an  easier 
path  along  the  Devonian  beds  to  the  west  of  the  old  lake  basin, 
and  is  seen  in  the  Little  Juniata,  flowing  along  the  outer  side 
of  Terrace  mountain  and  rounding  the  northern  synclinal  point 
where  Terrace  mountain  joins  Sideling  hill.  It  then  crosses 
Jack's  mountain  at  a  point  where  the  hard  Medina  sandstones  of 
the  mountain  were  still  buried  at  the  time  of  the  choice  of  this 
channel.  In  the  same  way  the  drainage  of  the  subordinate  basin, 
through  which  the  main  lake  discharged  eastward,  is  now  not 
along  the  axis  of  the  Juniata-Catawissa  syncline,  but  on  the  softer 
beds  along  one  side  of  it ;  and  along  the  southern  side,  because 
the  easier  escape  that  was  provided  for  it  lay  on  that  side, 
namely,  via  the  Tuscarora  and  Wiconisco  synclines,  as  already 
described.  The  much  broader  change  from  the  Anthracite  to 
the  Susquehanna  was  only  another  form  of  the  same  process. 
Taking  a  transverse  view  of  the  whole  system  of  central  folds,  it 
is  perceived  that  their  axes  descend  into  the  Anthracite  district 
from  the  east  and  rise  westward  therefrom ;  it  is  as  if  the  whole 
region  had  received  a  slight  transverse  folding,  and  the  trans- 
verse axis  of  depression  thus  formed  defined  the  initial  course  of 
the  first  master  stream.  But  this  master  stream  deserted  its 
original  course  on  the  transverse  axis  of  depression  because  a 
lateral  course  across  lowlands  on  softer  beds  was  opened  by 
its  side  streams ;  and  in  the  contest  on  these  lowlands  with  an 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    469 

external  stream,  the  Susquehanna,  the  upper  portion  of  the 
Anthracite  was  diverted  from  the  hard  rocks  that  had  appeared 
on  the  transverse  axis.  The  distance  of  diversion  from  the  axial 
to  the  lateral  course  in  this  case  was  great  because  of  the  gentle 
quality  of  the  transverse  folding ;  or,  better  said,  because  of  the 
gentle  dips  of  the  axes  of  the  longitudinal  folds.  This  appear- 
ance of  systematic  rearrangement  in  the  several  river  courses 
where  none  was  expected  is,  to  my  mind,  a  strong  argument 
in  favor  of  the  originally  consequent  location  of  the  rivers  and 
their  later  mutual  adjustment.  It  may  perhaps  be  conceived 
that  antecedent  streams  might  imitate  one  another  roughly  in 
the  attitude  that  they  prophetically  chose  with  regard  to  folds 
subsequently  formed,  but  no  reason  has  been  suggested  for  the 
imitation  being  carried  to  so  remarkable  and  definite  a  degree 
as  that  here  outlined. 

Superimposition  of  the  Susqtiekanna  on  Tivo  Synclinal  Ridges. 
There  is,  however,  one  apparently  venturesome  postulate  that 
may  have  been  already  noted  as  such  by  the  reader ;  unless  it 
can  be  reasonably  accounted  for  and  shown  to  be  a  natural  result 
of  the  long  sequence  of  changes  here  considered,  it  will  seriously 
militate  against  the  validity  of  the  whole  argument.  The  present 
course  of  the  middle  Susquehanna  leads  it  through  the  apical 
curves  of  two  Pocono  synclinal  ridges,  which  were  disregarded 
in  the  statement  given  above.  It  was  then  assumed  that  the 
embryonic  Susquehanna  gained  possession  of  the  Siluro-Devonian 
lowland  drainage  by  gnawing  out  a  course  to  the  west  of  these 
synclinal  points  ;  for  it  is  not  to  be  thought  of  that  any  conquest 
of  the  headwaters  of  the  Anthracite  river  could  have  been 
made  by  the  Susquehanna  if  it  had  had  to  gnaw  out  the  exist- 
ing four  traverses  of  the  Pocono  sandstones  before  securing  the 
drainage  of  the  lowlands  above  them.  The  backward  progress 
of  the  Susquehanna  could  not  in  that  case  have  been  nearly  fast 
enough  to  reach  the  Anthracite  before  the  latter  had  sunk  its 
channel  to  a  safe  depth.  It  is  therefore  important  to  justify  the 
assumption  as  to  the  more  westerly  location  of  the  embryonic 
Susquehanna,  and  afterwards  to  explain  how  it  should  have 
since  then  been  transferred  to  its  present  course.  A  short-cut 
through  all  this  roundabout  method  is  open  to  those  who  adopt 


470  PHYSIOGRAPHIC  ESSAYS 

in  the  beginning  the  theory  that  the  Susquehanna  was  an  ante- 
cedent river ;  but  as  I  have  said  at  the  outset  of  this  inquiry,  it 
seems  to  me  that  such  a  method  is  not  freer  from  assumption, 
even  though  shorter  than  the  one  here  adopted ;  and  it  has  the 
demerit  of  not  considering  all  the  curious  details  that  follow  the 
examination  of  consequent  and  adjusted  courses. 

The  sufficient  reason  for  the  assumption  that  the  embryonic 
Susquehanna  lay  farther  west  than  the  present  one  in  the  neigh- 
borhood of  the  Pocono  synclinals  is  simply  that  —  in  the  absence 
of  any  antecedent  stream  —  it  must  have  lain  there.  The  whole 
explanation  of  the  development  of  the  Siluro-Devonian  lowlands 
between  the  Pocono  and  Medina  ridges  depends  simply  on  their 
being  weathered  out  where  the  rocks  are  weak  enough  to  waste 
faster  than  the  inclosing  harder  ridges  through  which  the  streams 
escape.  In  this  process  the  streams  exercise  no  control  whatever 
over  the  direction  in  which  their  headwaters  shall  grow ;  they 
leave  this  entirely  to  the  structure  of  the  district  that  they  drain. 
It  thus  appears  that,  under  the  postulate  as  to  the  initial  location 
of  the  Susquehanna  as  one  of  the  many  streams  descending  the 
great  slope  of  the  Kittatinny  (Cumberland)  highland  into  the 
Swatara  syncline,  its  course  being  reversed  from  northward  to 
southward  by  the  Newark  depression,  we  are  required  to  suppose 
that  its  headwater  (northward)  growth  at  the  time  of  the  Jurassic 
elevation  must  have  been  on  the  Siluro-Devonian  beds,  so  as  to 
avoid  the  harder  rocks  on  either  side.  Many  streams  competed 
for  the  distinction  of  becoming  the  master,  and  that  one  gained 
its  ambition  whose  initial  location  gave  it  the  best  subsequent 
opportunity.  It  remains  then  to  consider  the  means  by  which 
the  course  of  the  conquering  Susquehanna  may  have  been  sub- 
sequently changed  from  the  lowlands  on  to  the  two  Pocono 
synclines  that  it  now  traverses.  Some  departure  from  its  early 
location  may  have  been  due  to  eastward  planation  in  its  advanced 
age,  when  it  had  large  volume  and  gentle  slope  and  was  there- 
fore swinging  and  cutting  laterally  in  its  lower  course.  This 
may  have  had  a  share  in  the  result,  but  there  is  another  process 
that  seems  to  me  more  effective. 

In  the  latter  part  of  the  Jura-Cretaceous  cycle  the  whole 
country  hereabout  suffered  a  moderate  depression,  by  which  the 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    471 

Atlantic  transgressed  many  miles  inland  from  its  former  shore- 
line, across  the  lowlands  of  erosion  that  had  been  developed  on 
the  littoral  belt.  Such  a  depression  must  have  had  a  distinct 
effect  on  the  lower  courses  of  the  larger  rivers,  which,  having 
already  cut  their  channels  down  close  to  base-level  and  opened 
their  valleys  wide  on  the  softer  rocks,  were  then  "  estuaried,"  or 
at  least  so  far  checked  as  to  build  wide  flood  plains  over  their 
lower  stretches.  Indeed,  the  flood  plains  may  have  been  begun 
at  an  earlier  date,  and  have  been  confirmed  and  extended  in  the 
later  time  of  depression.  Is  it  possible  that  in  the  latest  stage 
of  this  process  the  almost  base-leveled  remnants  of  Blue  moun- 
tain and  the  Pocono  ridges  could  have  been  buried  under  the 
flood  plain  in  the  neighborhood  of  the  river  ? 

If  this  be  admitted,  it  is  then  natural  for  the  river  to  depart 
from  the  line  of  its  buried  channel  and  cross  the  buried  ridges  on 
which  it  might  settle  down  as  a  superimposed  river  in  the  next 
cycle  of  elevation.  It  is  difficult  to  decide  such  general  questions 
as  these  ;  and  it  may  be  difficult  for  the  reader  to  gain  much  con- 
fidence in  the  efficacy  of  the  processes  suggested  ;  but  there  are 
certain  features  in  the  side  streams  of  the  Susquehanna  that 
lend  some  color  of  probability  to  the  explanation  as  offered. 

Admit,  for  the  moment,  that  the  aged  Susquehanna,  in  the 
later  part  of  the  Jura-Cretaceous  cycle,  did  change  its  channel 
somewhat  by  cutting  to  one  side,  or  by  planation,  as  it  is  called. 
Admit,  also,  that  in  the  natural  progress  of  its  growth  it  had 
built  a  broad  flood  plain  over  the  Siluro-Devonian  lowlands,  and 
that  the  depth  of  this  deposit  was  increased  by  the  formation  of 
an  estuarine  delta  upon  it  when  the  country  sank  at  the  time  of 
the  mid-Cretaceous  transgression  of  the  sea.  It  is  manifest  that 
one  of  the  consequences  of  all  this  might  be  the  peculiar  course 
of  the  river  that  is  to  be  explained,  namely,  its  superimposition 
on  the  two  Pocono  synclinal  ridges  in  the  next  cycle  of  its 
history,  after  the  Tertiary  elevation  had  given  it  opportunity  to 
rediscover  them.  It  remains  to  inquire  what  other  consequences 
should  follow  from  the  same  conditions,  and  from  these  to  devise 
tests  of  the  hypothesis. 

Evidence  of  Superimposition  in  the  Susquehanna  Tributaries. 
One  of  the  peculiarities  of  flood-plained  rivers  is  that  the  lateral 


! 


472  PHYSIOGRAPHIC  ESSAYS 

streams  shift  their  points  of  union  with  the  main  stream  farther 
and  farther  down  the  valley,  as  Lombardini  has  shown  in  the 
case  of  the  Po.  If  the  Susquehanna  were  heavily  flood- plained 
at  the  close  of  the  Jura-Cretaceous  cycle,  some  of  its  tributaries 
should  manifest  signs  of  this  kind  of  deflection  from  their  struc- 
tural courses  along  the  strike  of  the  rocks.  Side  streams  that 
once  joined  the  main  stream  on  the  line  of  some  of  the  softer 
northeast-southwest  beds,  leaving  the  stronger  beds  as  faint  hills 
on  either  side,  must  have  forgotten  such  control  after  it  was 
base-leveled  and  buried;  as  the  flood  plain  grew,  they  properly 
took  more  and  more  distinctly  downward-deflected  courses,  and 
these  deflections  should  be  maintained  in  subsequent  cycles  as 
superimposed  courses  independent  of  structural  guidance.  Such 
I  believe  to  be  the  fact.  The  downstream  deflection  is  so 
distinctly  a  peculiarity  of  a  number  of  tributaries  that  join  the 
Susquehanna  on  the  west  side  that  it  cannot  be  ascribed  to  ac- 
cident, but  must  be  referred  to  some  systematic  cause.  Exam- 
ples of  deflection  are  found  in  Penn's  creek,  Middle  creek,  and 
North  Mahantango  creek  in  Snyder  county;  West  Mahantango, 
between  the  latter  and  Juniata  county;  and  in  the  Juniata  and 
Little  Juniata  rivers  of  Perry  county.  On  the  other  side  of  the 
Susquehanna  the  examples  are  not  so  distinct,  but  the  following 
may  be  mentioned:  Delaware  and  Warrior  runs,  Chillisquaque 
creek  and  Little  Shamokin  creek,  all  in  Northumberland  county. 
It  may  be  remarked  that  it  does  not  seem  impossible  that  the 
reason  for  the  more  distinct  deflection  of  the  western  streams 
may  be  that  the  Susquehanna. is  at  present  east  of  its  old  course, 
and  hence  towards  the  eastern  margin  of  its  flood  plain,  as, 
indeed,  its  position  on  the  Pocono  synclinals  implies.  A  reason 
for  the  final  location  of  the  superimposed  river  on  the  eastern 
side  of  the  old  flood  plain  may  perhaps  be  found  in  the  eastward 
tilting  that  is  known  to  have  accompanied  the  elevation  of  the 
Cretaceous  lowland. 

It  follows  from  the  foregoing  that  the  present  lower  course  of 
the  Susquehanna  must  also  be  of  superimposed  origin,  for  the 
flood  plain  of  the  middle  course  must  have  extended  downstream 
to  its  delta,  and  there  have  become  confluent  with  the  sheet  of 
Cretaceous  sediments  that  covered  all  the  southeastern  lowland, 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    473 

over  which  the  sea  had  transgressed.  McGee  has  already  pointed 
out  indications  of  superimposed  stream  courses  in  the  south- 
eastern part  of  the  state  (a),  but  I  am  not  sure  that  he  would 
regard  them  as  of  the  date  here  referred  to. 

The  theory  of  the  location  of  the  Susquehanna  on  the  Pocono 
synclinal  ridges,  therefore,  stands  as  follows  :  The  general  posi- 
tion of  the  river  indicates  that  it  has  been  located  by  some 
process  of  slow  self-adjusting  development,  and  that  it  is  not  a 
persistent  antecedent  river ;  and  yet  there  is  no  reason  to  think 
that  it  could  have  been  brought  into  its  present  special  position 
by  any  process  of  shifting  divides.  The  processes  that  have 
been  suggested  to  account  for  its  special  location,  as  departing 
slightly  from  a  location  due  to  slow  adjustments  following  an 
ancient  consequent  origin,  call  for  the  occurrence  of  certain 
additional  peculiarities  in  the  courses  of  its  tributary  streams, 
entirely  unforeseen  and  unnoticed  until  this  point  in  the  inquiry 
is  reached ;  and  on  looking  at  the  map  to  see  if  they  occur, 
they  are  found  with  perfect  distinctness.  The  hypothesis  of 
superimposition  may  therefore  be  regarded  as  having  advanced 
beyond  the  stage  of  mere  suggestion  and  as  having  gained  some 
degree  of  confirmation  from  the  correlations  that  it  detects  and 
explains.  It  only  remains  to  ask  if  these  correlations  might  have 
originated  in  any  other  way,  and  if  the  answer  to  this  is  in  the 
negative,  the  case  may  be  looked  upon  as  having  a  fair  measure 
of  evidence  in  its  favor.  The  remaining  consideration  may  be 
taken  up  at  once  as  the  first  point  to  be  examined  in  the  Tertiary 
cycle  of  development. 

Events  of  the  Tertiary  Cycle.  The  elevation  given  to  the  region 
by  which  Cretaceous  base-leveling  was  terminated,  and  which  I 
have  called  the  early  Tertiary  elevation,  offered  opportunity  for 
the  streams  to  deepen  their  channels  once  more.  In  doing  so, 
certain  adjustments  of  moderate  amount  occurred,  which  will  be 
soon  examined.  As  time  went  on,  much  denudation  was  effected, 
but  no  widespread  base-leveling  was  reached,  for  the  Cretaceous 
crest  lines  of  the  hard  sandstone  ridges  still  exist.  The  Tertiary 
cycle  was  an  incomplete  one.  At  its  close,  lowlands  had  been 
opened  only  on  the  weaker  rocks  between  the  hard  beds.  Is  it 
not  possible  that  the  flood  plaining  of  the  Susquehanna  and  the 


474  PHYSIOGRAPHIC  ESSAYS 

downstream  deflection  of  its  branches  took  place  in  the  closing 
stages  of  this  cycle  instead  of  at  the  end  of  the  previous  cycle  ? 
If  so,  the  deflection  might  appear  on  the  branches,  but  the  main 
river  would  not  be  transferred  to  the  Pocono  ridges.  This  ques- 
tion may  be  safely  answered  in  the  negative  ;  for  the  Tertiary 
lowland  is  by  no  means  well  enough  base-leveled  to  permit  such 
an  event.  The  beds  of  intermediate  resistance,  the  Oriskany  and 
certain  Chemung  sandstones,  had  not  been  worn  down  to  base- 
level  at  the  close  of  the  Tertiary  cycle ;  they  had,  indeed,  lost 
much  of  the  height  that  they  possessed  at  the  close  of  the  previ- 
ous cycle,  but  they  had  not  been  reduced  as  low  as  the  softer 
beds  on  either  side.  They  were  only  reduced  to  ridges  of  moderate 
and  unequal  height  over  the  general  plain  of  the  Siluro-Devonian 
low  country,  without  great  strength  of  relief  but  quite  strong 
enough  to  call  for  obedience  from  the  streams  alongside  of  them. 
And  yet,  near  Selin's  grove,  for  example,  in  Snyder  county, 
Penn's  and  Middle  creeks  depart  most  distinctly  from  the  strike 
of  the  local  rocks  as  they  near  the  Susquehanna,  and  traverse 
certain  well-marked  ridges  on  their  way  to  the  main  river.  Such 
aberrant  streams  cannot  be  regarded  as  superimposed  at  the  close 
of  the  incomplete  Tertiary  cycle ;  they  cannot  be  explained  by 
any  process  of  spontaneous  adjustment  yet  described,  nor  can 
they  be  regarded  as  vastly  ancient  streams  of  antecedent  courses  ; 
I  am  therefore  much  tempted  to  consider  them  as  of  superim- 
posed origin,  inheriting  their  present  courses  from  the  flood-plain 
cover  of  the  Susquehanna  in  the  latest  stage  of  the  Jura- 
Cretaceous  cycle.  With  this  tentative  conclusion  in  mind  as  to 
the  final  events  of  Jura-Cretaceous  time,  we  may  take  up  the 
more  deliberate  consideration  of  the  work  of  the  Tertiary  cycle. 
The  chief  work  of  the  Tertiary  cycle  was  merely  the  opening 
of  the  valley  lowlands ;  little  opportunity  for  river  adjustment 
occurred  except  on  a  small  scale.  The  most  evident  cases  of 
adjustment  have  resulted  in  the  change  of  water  gaps  into  wind 
gaps,  of  which  several  examples  can  be  given,  the  one  best  known 
being  the  Delaware  Wind  Gap  between  the  Lehigh  and  Delaware 
Water  Gaps  in  Blue  mountain.  The  wind  gap  marks  the  unfinished 
notch  of  some  stream  that  once  crossed  the  ridge  here  and  whose 
headwaters  have  since  then  been  diverted,  probably  to  the  Lehigh. 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    475 

The  difficulty  in  the  case  is  not  at  all  how  the  stream  that  once 
flowed  here  was  diverted,  but  how  a  stream  that  could  be  diverted 
in  the  Tertiary  cycle  could  have  escaped  diversion  at  some  earlier, 
date.  The  relative  rarity  of  wind  gaps  indicates  that  nearly  all  of 
the  initial  lateral  streams,  which  may  have  crossed  the  ridges  at 
an  early  epoch  in  the  history  of  the  rivers,  have  been  beheaded 
in  some  cycle  earlier  than  the  Tertiary  and  their  gaps  thereafter 
obliterated.  Why  the  Delaware  Wind-Gap  stream  should  have 
endured  into  a  later  cycle  does  not  at  present  appear.  Other 
wind  gaps  of  apparently  similar  origin  may  be  found  in  Blue 
mountain,  west  of  the  Schuylkill  and  east  of  the  Susquehanna. 
It  is  noteworthy  that  if  any  small  streams  still  persevere  in  their 
gaps  across  a  hard  ridge,  they  are  not  very  close  to  any  large 
river  gap;  hence  it  is  only  at  the  very  headwaters  of  Conedog- 
winet  creek,  in  the  northern  part  of  Franklin  county,  that  any 
water  is  still  drawn  from  the  back  of  Blue  mountain.  Again, 
these  small  stream  gaps  do  not  lie  between  large  river  gaps  and 
wind  gaps,  but  wind  gaps  lie  between  the  gaps  of  large  rivers 
and  those  of  small  streams  that  are  not  yet  diverted.  Excellent 
illustration  of  this  is  found  on  the  "Piedmont  sheet"  of  the 
contoured  maps  issued  by  the  United  States  Geological  Survey. 
The  sheet  covers  part  of  Maryland  and  West  Virginia,  near 
where  the  North  Branch  of  the  Potomac  comes  out  of  the  plateau 
and  crosses  New  Creek  mountain.  Eleven  miles  south  of  the 
Potomac  gap  there  is  a  deep  wind  gap  ;  but  farther  on,  at  twenty, 
twenty-five,  and  twenty-nine  miles  from  the  river  gap,  are  three 
fine  water  gaps  occupied  by  small  streams.  This  example  merely 
shows  how  many  important  points  in  the  history  of  our  rivers 
will  be  made  clear  when  the  country  is  properly  portrayed  on 
contoured  maps. 

A  few  lines  may  be  given  to  the  general  absence  of  gaps  in 
Blue  mountain  in  Pennsylvania.  When  the  initial  consequent 
drainage  was  established,  many  streams  must  have  been  located 
on  the  northward  slope  of  the  great  Cumberland  highland,  CC 
(Fig.  31);  they  must  have  gullied  the  slope  to  great  depths  and 
carried  away  great  volumes  of  the  weak  Cambrian  beds  that  lay 
deep  within  the  hard  outer  casings  of  the  mass.  Minor  adjust- 
ments served  to  diminish  the  number  of  these  streams,  but  the 


476  PHYSIOGRAPHIC  ESSAYS 

more  effective  cause  of  their  present  rarity  lay  in  the  natural 
selection  of  certain  of  them  to  become  large  streams  ;  the  smaller 
ones  were  generally  beheaded  by  these.  The  only  examples  of 
streams  that  still  cross  this  ridge  with  their  initial  Permian  direc- 
tion of  flow  to  the  northwest  are  found  in  two  southern  branches 
of  Tuscarora  creek  at  the  southern  point  of  Juniata  county  ;  and 
these  survive  because  of  their  obscure  location  among  the  many 
Medina  ridges  of  that  district,  where  they  were  not  easily  access- 
ible to  capture  by  other  streams. 

Tertiary  Adjustment  of  the  Juniata  on  the  Medina  Anticlines. 
The  lower  course  of  the  Juniata  presents  several  examples  of 
adjustment  referable  to  the  last  part  of  the  Jura-Cretaceous  cycle 
and  to  the  Tertiary  cycle.  The  explanation  offered  for  the  escape 
of  this  river  from  its  initial  syncline  did  not  show  any  reason  for 
its  peculiar  position  with  respect  to  the  several  Medina  anticlines 
that  it  now  borders,  because  at  the  time  when  it  was  led  across 
country  to  the  Wiconisco  syncline,  the  hard  Medina  beds  of  these 
anticlines  were  not  discovered.  It  is  therefore  hardly  to  be 
thought  that  the  location  of  the  Juniata  in  the  Narrows  below 
Lewistown,  between  Blue  Ridge  and  Shade  mountains,  and  its 
avoidance  of  Tuscarora  mountain,  could  have  been  denned  at 
that  early  date.  But  all  these  Medina  anticlines  rise  more  or  less 
above  the  Cretaceous  base-level,  and  must  have  had  some  effect 
on  the  position  taken  by  the  river  about  the  middle  of  that  cycle 
when  its  channel  sank  upon  them.  Blue  Ridge  and  Black  Log 
anticlines  rise  highest.  The  first  location  of  the  cross-country 
stream  that  led  the  early  Juniata  away  from  its  initial  syncline 
probably  traversed  the  Blue  Ridge  and  Black  Log  anticlines 
while  they  were  yet  buried ;  but  its  channel  cutting  was  much 
retarded  on  encountering  them,  and  some  branch  stream  working 
around  from  the  lower  side  of  the  obstructions  may  have  diverted 
the  river  to  an  easier  path.  The  only  path  of  the  kind  is  the 
narrow  one  between  the  overlapping  anticlines  of  Blue  Ridge 
and  Shade  mountains,  and  there  the  Juniata  now  flows.  If 
another  elevation  should  occur  in  the  future,  it  might  happen 
that  the  slow  deepening  of  the  channel  in  the  hard  Medina 
beds  which  now  floor  the  Narrows  would  allow  Middle  creek 
of  Snyder  county  to  tap  the  Juniata  at  Lewistown  and  lead 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA  477 

it  by  direct  course  past  Middleburgh  to  the  Susquehanna ;  thus 
it  would  return  to  the  path  of  its  youth. 

The  location  of  the  Juniata  at  the  end  of  Tuscarora  mountain 
is  again  so  definite  that  it  can  hardly  be  referred  to  a  time  when 
the  mountain  had  not  been  revealed.  The  most  likely  position 
of  the  original  cross-country  stream  which  brought  the  Juniata 
into  the  Wiconisco  syncline  was  somewhere  on  the  line  of  the 
existing  mountain,  and  assuming  it  to  have  been  there,  we  must 
question  how  it  has  been  displaced.  The  process  seems  to  have 
been  of  the  same  kind  as  that  just  given ;  the  retardation  of 
channel  cutting  in  the  late  Cretaceous  cycle,  when  the  Medina 
beds  of  Tuscarora  anticline  were  discovered,  allowed  a  branch 
from  the  lower  part  of  the  river  to  work  around  the  end  of  the 
mountain  and  lead  the  river  out  that  way.  The  occurrence  of  a 
shallow  depression  across  the  summit  of  the  otherwise  remarkably 
even  crest  of  Tuscarora  mountain  suggests  that  this  diversion 
was  not  finally  accomplished  until  shortly  after  the  Tertiary 
elevation  of  the  country ;  but  at  whatever  date  the  adjustment 
occurred,  it  is  natural  that  it  should  pass  around  the  eastern 
-end  of  the  mountain  and  not  around  the  western  end,  where 
the  course  would  have  been  much  longer  and,  therefore,  not 
successfully  to  be  taken  by  a  diverting  stream. 

While  the  quality  of  these  processes  appears  satisfactory,  I  am 
not  satisfied  as  to  the  sufficiency  of  their  quantity.  If  diversion 
was  successfully  practiced  at  the  crossing  of  the  Tuscarora  anti- 
cline, why  not  also  at  the  crossing  of  Jack's  mountain  anticline, 
on  which  the  river  still  perseveres  ?  It  is  difficult  here  to  decide 
how  much  confidence  may  be  placed  in  the  explanation,  because 
of  its  giving  reason  for  the  location  of  certain  streams,  and  how 
much  doubt  must  be  cast  upon  it  because  it  seems  impossible 
and  is  not  of  universal  application. 

Migration  of  the  Atlantic-Ohio  Divide.  There  are  certain 
shifted  courses  which  cannot  be  definitely  referred  to  any  par- 
ticular cycle,  and  which  may  therefore  be  mentioned  now. 
Among  the  greatest  are  those  by  which  the  divide  between  the 
Atlantic  and  the  Ohio  streams  has  been  changed  from  its  initial 
position  on  the  great  constructional  Nittany  highland  and  Bed- 
ford range.  There  was  probably  no  significant  change  until  after 


478  PHYSIOGRAPHIC  ESSAYS 

the  Newark  depression,  for  the  branches  of  the  Anthracite  river 
could  not  have  begun  to  push  the  divide  westward  till  after  the 
eastward  flow  of  the  river  was  determined ;  until  then,  there 
does  not  seem  to  have  been  any  marked  advantage  possessed  by 
the  eastward  streams  over  the  westward.  But  with  the  eastward 
escape  of  the  Anthracite,  it  probably  found  a  shorter  course  to 
the  sea  and  one  that  led  it  over  alternately  soft  and  hard  rocks, 
instead  of  the  longer  course  followed  by  the  Ohio  streams  over 
continuous  sandstones.  The  advantage  given  by  the  greater  ex- 
tent of  soft  beds  is  indicated  by  the  great  breadth  of  the  existing 
valleys  in  the  central  district  compared  with  the  less  breadth  of 
those  in  the  plateau  to  the  west.  Consider  the  effect  of  this 
advantage  at  the  time  of  the  Jurassic  elevation.  As  the  streams 
on  the  eastern  slope  of  the  Nittany  divide  had  the  shortest  and 
steepest  courses  to  the  sea,  they  deepened  their  valleys  faster 
than  those  on  the  west  and  acquired  drainage  area  from  them  ; 
hence  we  find  reason  for  the  drainage  of  the  entire  Nittany  and 
Bedford  district  by  the  Atlantic  streams  at  present.  Various 
branches  of  what  are  now  the  Allegheny  and  Monongahela  origi- 
nally rose  on  the  western  slope  of  the  dividing  range.  These 
probably  reached  much  farther  east  in  pre-Permian  time,  but  had 
their  headwaters  turned  another  way  by  the  growth  of  the  great 
anticlinal  divide ;  but  the  smaller  anticlines  of  Laurel  ridge  and 
Negro  mountain  farther  west  do  not  seem  to  have  been  strong 
enough  to  form  a  divide,  for  the  rivers  still  traverse  them.  Now, 
as  the  headwaters  of  the  Juniata  breached  the  eastern  slope  of 
the  Nittany-Bedford  range  and  pushed  the  divide  westward,  they 
at  last  gained  possession  of  the  Siluro-Devonian  monocline  on 
its  western  slope ;  but  beyond  this  it  has  not  been  possible  for 
them  yet  to  go.  As  the  streams  cut  down  deeper  and  encoun- 
tered the  Medina  anticline  near  the  core  of  the  ridge,  they  sawed 
a  passage  through  it ;  the  Cambrian  beds  were  discovered  below 
and  a  valley  was  opened  on  them  as  the  Medina  cover  wore  away. 
The  most  important  point  about  this  is  that  we  find  in  it  an  ade- 
quate explanation  of  the  opposite  location  of  water  gaps  in  pairs, 
such  as  characterize  the  branches  of  the  Juniata,  below  Tyrone, 
and  again  below  Bedford.  This  opposite  location  has  been  held 
to  indicate  an  antecedent  origin  of  the  river  that  passes  through 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    479 

the  gaps,  while  gaps  formed  by  self-developed  streams  are  not 
thought  to  present  such  correspondence  (Hilber).  Yet  this 
special  case  of  paired  gaps  in  the  opposite  walls  of  a  breached 
anticline  is  manifestly  a  direct  sequence  of  the  development  of 
the  Juniata  headwaters.  The  settling  down  of  the  main  Juniata 
on  Jack's  mountain  anticline  below  Huntingdon  is  another  case 
of  the  same  kind,  in  which  the  relatively  low  anticlinal  crest  is  as 
yet  not  widely  breached ;  the  gaps  below  Bedford  stand  apart, 
as  the  crest  is  there  higher,  and  hence  wider  opened  ;  and  the 
gaps  below  Tyrone  are  separated  by  some  ten  or  twelve  miles. 

When  the  headwater  streams  captured  the  drainage  of  the 
Siluro-Devonian  monocline  on  the  western  side  of  the  ancient 
dividing  anticline,  they  developed  subsequent  rectangular 
branches  growing  like  a  well-trained  grapevine.  Most  of  this 
valley  has  been  acquired  by  the  West  Branch  of  the  Susque- 
hanna,  probably  because  it  traversed  the  Medina  beds  less 
often  than  the  Juniata.  For  the  same  reason  it  may  be,  the 
West  Branch  has  captured  a  considerable  area  of  plateau 
drainage  that  must  have  once  belonged  to  the  Ohio,  while 
the  Juniata  has  none  of  it ;  but  if  so,  the  capture  must  have 
been  before  the  Tertiary  cycle,  for  since  that  time  the  ability 
of  the  West  Branch  and  of  the  Juniata  as  regards  such  capture 
appears  about  alike.  On  the  other  hand,  Castleman's  river,  a 
branch  of  the  Monongahela,  still  retains  the  drainage  of  a  small 
bit  of  the  Siluro-Devonian  monocline,  at  the  southern  border 
of  the  state,  where  the  Juniata  headwaters  had  the  least  oppor- 
tunity to  capture  it ;  but  the  change  here  is  probably  only 
retarded,  not  prevented  entirely ;  the  Juniata  will  some  day 
push  the  divide  even  here  back  to  the  Allegheny  Front,  the 
frontal  bluff  of  the  plateau. 

Other  Examples  of  •  Adjustments.  Other  examples  of  small 
adjustments  are  found  around  the  Wyoming  basin  (Fig.  36). 
Originally  all  these  streams  ran  centripetally  down  the  inclosing 
slopes,  and  in  such  locations  they  must  have  cut  gullies  and 
breaches  in  the  hard  Carboniferous  beds  and  opened  low  back 
country  on  the  weaker  Devonians.  Some  of  the  existing  streams 
still  do  so,  and  these  are  precisely  the  ones  that  are  not  easily 
reached  by  divertors.  The  Susquehanna  in  its  course  outside 


480 


PHYSIOGRAPHIC  ESSAYS 


of  the  basin  has  sent  out  branches  that  have  beheaded  all  the 
centripetal  streams  within  reach ;  where  the  same  river  enters 
the  basin,  the  centripetal  streams  have  been  shortened  if  not 
completely  beheaded.  A  branch  of  the  Delaware  has  captured 
the  heads  of  some  of  the  streams  near  the  eastern  end  of  the 
basin.  Elsewhere,  the  centripetal  streams  still  exist  of  good 
length.  The  contrast  between  the  persistence  of  some  of  the 
centripetal  streams  here  and  their  peripheral  diversion  around 
Broad  Top  is  a  consequence  of  the  difference  of  altitude  of  the 


FIG.  36 

old  lake  bottoms  in  the  two  cases.  It  is  not  to  be  doubted  that 
we  shall  become  acquainted  with  many  examples  of  this  kind  as 
our  intimacy  with  rivers  increases. 

Events  of  the  Quaternary  Cycle.  The  brief  quaternary  cycle 
does  not  offer  many  examples  of  the  kind  that  we  have  con- 
sidered, and  all  that  are  found  are  of  small  dimensions.  The 
only  capturing  stream  that  need  be  mentioned  has  lately  been 
described  as  a  "  river  pirate"  (Davis,  $);  but  its  conquest  is  only 
a  Schleswig-Holstein  affair  compared  to  the  Goth-  and  Hun-like 
depredations  of  the  greater  streams  in  earlier  cycles. 

The  character  of  the  streams  and  their  valleys  as  they  now 
exist  is  strikingly  dependent  in  many  ways  on  the  relation  of  the 
incipient  quaternary  cycle  to  the  longer  cycles  of  the  past.  No 
lakes  occur,  exception  being  made  only  of  the  relatively  small 
ponds  due  to  drift  obstruction  within  the  glaciated  area.  Water- 
falls are  found  only  at  the  headwaters  of  small  streams  in  the 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    481 

plateau  district,  exception  again  being  made  only  for  certain  cases 
of  larger  streams  that  have  been  thrown  from  their  pre-glacial 
courses  by  drift  barriers,  and  which  are  now  in  a  very  immature 
state  on  their  new  lines  of  flow.  The  small  valleys  of  this  cycle 
are  shallow  and  narrow,  always  of  a  size  strictly  proportional  to 
the  volume  of  the  stream  and  the  hardness  of  the  inclosing 
rocks,  exception  being  made  only  in  the  case  of  post-glacial  gorges 
whose  streams  have  been  displaced  from  their  pre-glacial  chan- 
nels. The  terraces  that  are  seen,  especially  on  the  streams  that 
flow  in  or  from  the  glaciated  district,  are  merely  a  temporary  and 
subordinate  complication  of  the  general  development  of  the  val- 
leys. In  the  region  that  has  been  here  considered,  the  streams 
have  been  seldom  much  displaced  from  their  pre-glacial  channels ; 
but  in  the  northwestern  part  of  the  state,  where  the  drift  in  the 
valleys  seems  to  be  heavier,  more  serious  disturbance  of  pre- 
glacial  courses  is  reported.  The  facts  here  referred  to  in  regard 
to  lakes,  falls,  gorges,  terraces,  and  displaced  streams  are  to  be 
found  in  the  various  volumes  of  the  Second  Geological  Survey 
of  the  State  (especially  Carll,  Reports  I3,  I4 ;  White,  Reports 
G5,  G6 ;  Lewis,  Report  Z) ;  in  regard  to  the  terraces  and  the 
estuarine  deflections  of  the  Delaware  and  Susquehanna,  refer- 
ence should  be  made  also  to  McGee's  studies  (#,  c). 

Doubtful  Cases.  It  is  hardly  necessary  to  state  that  there  are 
many  facts  for  which  no  satisfactory  explanation  is  found  under 
the  theory  of  adjustments  that  we  have  been  considering.  Some 
will  certainly  include  the  location  of  the  Susquehanna  on  the 
points  of  the  Pocono  synclines  under  this  category  ;  all  must 
feel  that  such  a  location  savors  of  an  antecedent  origin.  The 
same  is  true  of  the  examples  of  the  alignment  of  water  gaps 
found  on  certain  streams ;  for  example,  the  four  gaps  cut  in  the 
two  pairs  of  Pocono  and  Pottsville  outcrops  at  the  west  end 
of  the  Wyoming  syncline,  and  the  three  gaps  where  the  Little 
Schuylkill  crosses  the  coal  basin  at  Tamaqua ;  the  opposite  gaps 
in  pairs  at  Tyrone  and  Bedford  have  already  been  sufficiently 
explained.  The  location  of  the  upper  North  Branch  of  the 
Susquehanna  is  also  unrelated  to  processes  of  adjustment  as 
far  as  I  can  see  them,  and  the  great  area  of  plateau  drainage 
that  is  now  possessed  by  the  West  Branch,  is  certainly  difficult 


482  PHYSIOGRAPHIC  ESSAYS 

to  understand  as  the  result  of  conquest.  The  two  independent 
gaps  in  Tussey's  mountain,  maintained  by  the  Juniata  and  its 
Frankstown  branch  below  Tyrone,  are  curious,  especially  in  view 
of  the  apparent  diversion  of  the  branch  to  the  main  stream 
on  the  upper  side  of  Warrior's  ridge  (Oriskany),  just  east  of 
Tussey's  mountain. 

Complicated  History  of  our  Actual  Rivers.  If  this  theory  of 
the  history  of  our  rivers  is  correct,  it  follows  that  any  one  river 
as  it  now  exists  is  of  so  complicated  an  origin  that  its  develop- 
ment cannot  become  a  matter  of  general  study  and  must  unhap- 
pily remain  only  a  subject  for  special  investigation  for  some  time 
to  come.  It  was  my  hope  on  beginning  this  essay  to  find  some 
teachable  sequence  of  facts  that  would  serve  to  relieve  the  usual 
routine  of  statistical  and  descriptive  geography,  but  this  is  not 
the  result  that  has  been  attained.  The  history  of  the  Susque- 
hanna,  the  Juniata,  or  the  Schuylkill  is  too  involved  with  com- 
plex changes,  if  not  enshrouded  in  mystery,  to  become  intelligible 
to  any  but  advanced  students  ;  only  the  simplest  cases  of  river 
development  can  be  introduced  into  the  narrow  limits  of  ordinary 
instruction.  The  single  course  of  an  ancient  stream  is  now  broken 
into  several  independent  parts ;  witness  the  disjointing  and  di- 
version of  the  original  Juniata,  which,  as  I  have  supposed,  once 
extended  from  Broad  Top  lake  to  the  Catawissa  basin.  Now  the 
upper  part  of  the  stream,  representing  the  early  Broad  Top  outlet, 
is  reduced  to  small  volume  in  Aughwick  creek  ;  the  continuation 
of  the  stream  to  Lewistown  is  first  set  to  one  side  of  its  original 
axial  location  and  is  then  diverted  to  another  syncline  ;  the  be- 
headed portion  now  represented  by  Middle  creek  is  diverted  from 
its  course  to  the  Catawissa  basin  by  the  Susquehanna ;  perhaps 
the  Catawissa  of  the  present  day  represents  the  reversed  course 
of  the  lower  Juniata  where  it  joined  the  Anthracite.  This  unserv- 
iceably  complicated  statement  is  not  much  simplified  if,  instead 
of  beginning  with  an  original  stream  and  searching  out  its  pres- 
ent disjointed  parts,  we  trace  the  composition  of  a  single  existing 
stream  from  its  once  independent  parts.  The  Juniata  of  to-day 
consists  of  headwaters  acquired  from  Ohio  streams ;  the  lake  in 
which  the  river  once  gathered  its  upper  branches  is  now  drained, 
and  the  lake  bottom  has  become  a  mountain  top ;  the  streams 


THE  RIVERS  AND  VALLEYS  OF  PENNSYLVANIA    483 

flow  around  the  margin  of  the  lake,  not  across  its  basin ;  a  short 
course  towards  Lewistown  nearly  coincides  with  the  original 
location  of  the  stream,  but  to  confound  this  with  a  precise  agree- 
ment is  to  lose  the  true  significance  of  river  history ;  the  lower 
course  is  the  product  of  diversion  at  least  at  two  epochs  and 
certainly  in  several  places ;  and  where  the  river  now  joins  the 
Susquehanna,  it  is  suspected  of  having  a  superimposed  course 
unlike  any  of  the  rest  of  the  stream.  This  is  too  complicated, 
even  if  it  should  ever  be  demonstrated  to  be  wholly  true,  to 
serve  as  material  for  ordinary  study ;  but  as  long  as  it  has  a 
savor  of  truth,  and  as  long  as  we  are  ignorant  of  the  whole  his- 
tory of  our  rivers,  through  which  alone  their  present  features 
can  be  rightfully  understood,  we  must  continue  to  search  after 
the  natural  processes  of  their  development  as  carefully  and 
thoroughly  as  the  biologist  searches  for  the  links  missing  from 
his  scheme  of  classification. 

Provisional  Conclusion.  It  is  in  view  of  these  doubts  and 
complications  that  I  feel  that  the  history  of  our  rivers  is  not 
yet  settled ;  but  yet  the  numerous  accordances  of  actual  and 
deductive  locations  appear  so  definite  and  in  some  cases  so 
remarkable  that  they  cannot  be  neglected,  as  they  must  be  if 
we  should  adhere  to  the  antecedent  origin  of  the  river  courses. 

The  method  adopted  on  an  early  page  therefore  seems  to  be 
justified.  The  provisional  system  of  ancient  consequent  drain- 
age, illustrated  in  Fig.  31,  does  appear  to  be  sufficiently  related 
to  the  streams  of  to-day  to  warrant  the  belief  that  most  of  our 
rivers  took  their  first  courses  between  the  primitive  folds  of  our 
mountains,  and  that  from  that  distant  time  to  the  present  the 
changes  they  have  suffered  are  due  to  their  own  interaction,  — 
to  their  own  mutual  adjustment  more  than  to  any  other  cause. 
The  Susquehanna,  Schuylkill,  Lehigh,  and  Delaware  are  com- 
pound, composite,  and  highly  complex  rivers,  of  repeated  mature 
adjustment.  The  middle  Susquehanna  and  its  branches  and  the 
upper  portions  of  the  Schuylkill  and  Lehigh  are  descendants  of 
original  Permian  rivers  consequent  on  the  constructional  topog- 
raphy of  that  time ;  Newark  depression  reversed  the  flow  of 
some  of  the  transverse  streams,  and  the  spontaneous  changes 
or  adjustments  from  immature  to  mature  courses  in  the  several 


484  PHYSIOGRAPHIC  ESSAYS 

cycles  of  development  are  so  numerous  and  extensive  that,  as 
Lowl  truly  says,  the  initial  drainage  has  almost  disappeared. 
The  larger  westward-flowing  streams  of  the  plateau  are  of 
earlier,  Carboniferous  birth,  and  have  suffered  little  subsequent 
change  beyond  a  loss  of  headwaters.  The  lower  courses  of  the 
Atlantic  rivers  are  younger,  having  been  much  shifted  from 
their  Permian  or  pre-Permian  courses  by  Newark  and  Cretaceous 
superimposition,  as  well  as  by  recent  downward  deformation  of 
the  surface  in  their  existing  estuaries.  No  recognizable  remnant 
of  rivers  antecedent  to  the  Permian  deformation  are  found  in 
the  central  part  of  the  state ;  and  with  the  exception  of  parts  of 
the  upper  Schuylkill  and  of  the  Susquehanna  near  Wilkesbarre, 
there  are  no  large  survivors  of  Permian  consequent  streams  in 
the  ordinary  meaning  of  the  term  ''consequent."  The  shifting 
of  courses  in  the  progress  of  mature  adjustment  has  had  more 
to  do  with  determining  the  actual  location  of  our  rivers  and 
streams  than  any  other  process. 

REFERENCES 

Davis,  W.  M.   (a)  "Origin  of  Cross- Valleys."    Science,  I  (1883),  325. 

(b)  Science,  XIII  (1889),  108. 

Hilber,  V.    Petermanns  Mittheilungen,  XXXV  (1889),  13. 
Lesley,  J.  P.  Proc.  Am.  Phil.  Soc.,  XIII  (1.873),  6. 
Lowl,  F.    (a)  Petermanns  Mittheilungen,  XXVIII  (1882),  405. 

(b)  Uber  Thalbildung.    Prag.  1884. 
McGee,  W.  J.   (a)  Am.  Jour.  Set.,  XXXV  (1888),  121,  134. 

(b)  Ibid.,  367,  448. 

(c)  U.  S.  Geol.  Surv.,  VII  Ann.  Rep.  (1888),  545. 
Peschel,  O.  F.    Physische  Erdkunde,  II  (1880),  442. 
Philippson,  A.    Studien  iiber  Wasserscheiden,  149.    Leipzig,  1886. 
Powell,  J.  W.    (a)  Exploration  of  the  Colorado  River  of  the  West,  153, 

163-166.     1875. 

(£)  Geology  of  the  Uinta  Mountains,  196.    1876. 
Tietze,  E.  Jahrbuch  Geol.  Reichsanstalt,  XXVIII  (1878),  600. 


XX 

THE  RIVERS  OF  NORTHERN  NEW  JERSEY 

WITH  NOTES  ON  THE  CLASSIFICATION 

OF  RIVERS  IN  GENERAL 

Northern  New  Jersey  is  drained  by  several  streams  which 
rise  in  the  Archaean  highlands,  flow  southeastward  across  the 
central  Triassic  plain,  and  reach  the  sea  near  the  inland  margin 
of  the  Cretaceous  formation. 

What  kinds  of  rivers  are  these  ?  Such  a  question  can  hardly 
be  answered  until  we  have  examined  rivers  in  many  parts  of  the 
world,  gaining  material  for  a  general  history  of  rivers  by  induc- 
tion from  as  large  a  variety  of  examples  as  possible  ;  and  until 
we  have  deduced  from  our  generalizations  a  series  of  critical 
features  sufficient  to  serve  for  the  detection  of  rivers  of  dif- 
ferent kinds  wherever  found. 

The  generalizations  here  referred  to  may  be  presented  in  the 
form  of  a  classification,  following  the  ideas  of  Powell,  Gilbert, 
Heim,  Lowl,  and  others,  as  follows  : 

Consequent  Rivers.  Those  that  have  in  their  birth,  at  the 
time  of  their  original  establishment  on  the  country  which  they 
drain,  selected  courses  in  accordance  with  the  constructional 
slopes  of  the  surface ;  for  example,  the  Red  River  of  the  North 
and  such  of  its  branches  as  flow  on  the  even  surface  of  the 
lacustrine  plain  of  Lake  Agassiz  ;  the  several  streams  that  drain 
the  broken  lava  blocks  of  southern  Oregon ;  certain  streams  and 
rivers  of  the  Jura  that  drain  the  synclinal  troughs  of  those  moun- 
tains. Consequent  streams  may  be  divided  into  definite  and 
indefinite  groups.  Definite  consequent  streams  are  those  that 
follow  well-defined  constructional  channels,  such  as  the  axial 
line  of  a  synclinal  trough,  or  the  lowest  point  of  an  anticlinal 
arch  between  two  synclinal  basins ;  they  are  defined  in  location 
as  well  as  in  direction.  Indefinite  consequent  streams  are  those 

485 


486  PHYSIOGRAPHIC  ESSAYS 

that  flow  down  constructional  slopes,  such  as  the  flanks  of  an 
anticline,  but  whose  precise  location  depends  on  those  minor 
inequalities  of  surface  that  we  term  "accidental";  they  are  de- 
fined in  direction  but  not  in  location,  and  they  are  as  a  rule 
branches  of  definite  consequent  streams. 

Antecedent  Rivers.  Those  that  during  and  for  a  time  after  a 
disturbance  of  their  drainage  area  maintain  the  courses  that  they 
had  taken  before  the  disturbance.  In  Powell's  original  definition 
of  this  class  of  rivers,  he  said  that  the  valleys  of  the  Uinta 
mountains  are  occupied  by  "  drainage  that  was  established 
antecedent  to  the  corrugation  or  displacement  of  the  beds  by 
faulting  or  folding"  (a,  163).  No  limit  is  set  to  the  amount  of 
corrugation  or  displacement  or  to  the  strength  of  the  faulting 
or  folding.  It  therefore  seems  advisable  to  consider  what  varia- 
tions there  may  be  from  the  strongly  marked  antecedent  type ; 
one  extreme  being  in  those  cases  where  the  displacement  was  a 
minimum  and  the  perseverance  of  the  streams  a  maximum,  the 
other  where  the  displacement  was  a  maximum  and  the  successful 
perseverance  of  the  streams  a  minimum,  or  zero.  The  simplest 
examples  of  antecedent  rivers  are  therefore  found  in  regions  that 
have  been  broadly  elevated  with  the  gentlest  changes  of  slope, 
so  as  to  enter  a  new  cycle  of  topographical  development,  all  the 
streams  retaining  their  previous  courses,  but  gaining  ability  to 
deepen  their  former  channels  down  to  the  new  base-level ;  such 
streams  maybe  called  "  revived."  Examples  of  revived  streams 
are  very  common  ;  nearly  all  the  streams  of  the  highlands  of  New 
Jersey  are  of  this  kind  ;  all  the  streams  of  central  and  western 
Pennsylvania  seem  to  belong  in  the  same  class.  From  these  simple 
and  common  examples  we  shall  some  day,  when  our  knowledge  of 
rivers  is  better  developed,  be  able  to  form  a  complete  series  lead- 
ing to  what  is  generally  understood  as  the  typical  antecedent 
river,  which  has  outlived  deformation  as  well  as  elevation  without 
suffering  either  deflection  or  ponding.  Large  rivers  of  strong 
slope,  well  inclosed  in  steep-sided  valleys,  or,  in  other  words, 
vigorous  adolescent  rivers,  have  the  best  opportunity  to  persist 
across  a  belt  of  rising  or  writhing  country,  because  a  great  def- 
ormation would  be  required  to  throw  them  from  their  courses. 
Small  streams  or  large  ones  of  faint  slope  in  an  open  low  country 


THE  RIVERS  OF  NORTHERN  NEW  JERSEY         487 

are  more  easily  deflected.  From  the  typical  antecedent  river  the 
series  may  be  continued  by  examples  in  which  even  the  larger 
streams  are  less  or  more  ponded  or  deflected  by  the  deformation, 
until  at  the  end  of  the  series  there  is  a  complete  extinction  of 
the  antecedent  drainage  and  the  e.stablishment  of  an  entirely 
original  consequent  drainage.  The  perfectly  typical  antecedent 
river,  in  the  middle  of  this  series,  is  certainly  of  rare  occurrence, 
and  is  perhaps  unknown. 

Superimposed  Rivers.  Consequent  streams,  whose  course  is 
taken  on  a  relatively  thin,  unconformably  overlying  mass,  for  a 
time  preserve  their  initial  courses,  even  though  they  may  be  quite 
out  of  accord  with  the  underlying  structures  on  which  they  have 
descended.  Such  streams  were  first  recognized  by  Marvine,  and 
afterwards  named  ''superimposed,"  ''inherited,"  or  "epigenetic" 
by  various  authors.  A  full  collection  of  examples  of  this  class 
should  begin  with  streams  that  depart  from  true  consequent 
courses  only  locally,  where  they  have  discovered  a  small  portion  of 
the  underlying  formation,  like  the  Merrimac  at  Manchester  and 
other  water-power  towns  of  New  Hampshire,  where  the  stream 
has  sunk  upon  rocky  ledges  beneath  the  surface  drift  and  sands  ; 
or  like  the  Mississippi  and  other  rivers  in  Minnesota  which  have  in 
places  cut  through  the  drift  sheet  to  the  underlying  crystallines. 
The  series  would  conclude  with  streams  that  have  stripped  off 
the  cover  on  which  they  were  consequent,  and  have  thus  become 
superimposed  on  the  underlying  formation  in  their  whole  length. 

There  is  a  curious  intermediate  type  of  drainage  lately  recog- 
nized by  McGee  in  the  southern  states,  a  superimposed  drainage 
that  is  not  inconsequent  upon  the  buried  surface  beneath  the 
unconformably  overlying  surface  layer.  It  occurs  in  regions 
where  a  well-marked  drainage  had  been  established  ;  a  brief  sub- 
mergence then  allowed  the  deposition  of  a  relatively  thin  mask 
of  sediments  ;  an  elevation  brought  the  masked  surface  up  again, 
and  as  it  rose,  the  streams  took  possession  of  lines  essentially 
identical  with  the  courses  of  their  ancestors,  because  the  mask 
of  newer  deposits  had  not  extinguished  the  antecedent  topog- 
raphy. McGee  proposes  to  call  such  streams  "  resurrected." 

Subsequent  Rivers.  Rivers  of  all  classes  as  a  rule  develop 
during  their  adolescence  and  more  mature  growth  certain 


488  PHYSIOGRAPHIC  ESSAYS 

"subsequent"  branches  that  were  not  in  any  way  represented  in 
the  early  youth  of  the  system.  Thus  the  indefinite  members  of  the 
consequent  drainage  of  the  Jura  mountains  have  developed  sub- 
sequent streams  on  soft  beds  of  monoclinal  and  anticlinal  struc- 
tures, where  there  could  not  possibly  have  been  any  consequent 
drainage  lines  at  the  birth  of  this  system,  unless  we  admit  the 
supposed  fracturing  of  the  anticlinal  crests,  which  seem  unneces- 
sary, to  say  the  least.  Even  in  the  simplest  style  of  drainage, 
growing  on  a  level  surface,  many  of  the  branches  must  be 
"  subsequent,"  or  as  McGee  has  called  them  in  such  cases, 
"  autogenetic." 

Adjusted  Rivers.  Rivers  of  all  classes  are  subject  to  sponta- 
neous rearrangement  or  adjustment  of  their  courses  to  a  greater 
or  less  extent,  in  accordance  with  the  weaker  structural  lines. 
This  results  from  the  migration  of  divides  and  the  consequent 
abstraction  or  capture  of  one  stream  by  another.  The  capture 
is  generally  made  by  the  head  ward  development  of  some  subse- 
quent branch.  But  after  this  kind  of  change  has  advanced  to  a 
certain  extent,  the  divides  become  stable,  and  further  change 
ceases.  The  rivers  may  then  be  said  to  be  maturely  adjusted. 
Under  certain  conditions,  chiefly  great  initial  altitude  of  surface, 
and  great  diversity  of  structure,  that  is,  in  mountainous  regions, 
the  changes  arising  from  adjustments  of  this  spontaneous  kind 
are  very  great,  so  that  the  courses  of  a  river's  middle  age  may 
have  very  little  resemblance  to  those  of  its  youth,  as  Lowl  has 
pointed  out  and  as  I  have  tried  to  show  in  the  case  of  the  Penn- 
sylvania rivers.  It  may  be  difficult  to  recognize  in  such  cases 
whether  the  youthful  courses  of  a  river  system  were  consequent, 
antecedent,  or  superimposed.  Adjustments  of  this  kind  were  not 
discussed  by  Powell,  although  he  makes  brief  mention  of  what 
I  have  called  subsequent  streams.  The  first  appreciation  that  I 
gained  of  river  adjustments  came  from  the  writings  of  Lowl ; 
but  I  have  since  found  that  the  general  principles  governing  their 
opportunity  were  stated  by  Gilbert  in  his  monograph  on  the 
"Henry  Mountains  of  Utah"  (141,  149),  and  by  Heim  in  his 
"  Mechanismus  der  Gebirgsbildung"  (/,  272,  etc.;  ii,  79,  320). 

Where  do  the  rivers  of  northern  New  Jersey  stand  in  this 
general  scheme  of  river  classification  ?  We  must  again  postpone 


THE  RIVERS  OF  NORTHERN   NEW  JERSEY         489 

the  answer  to  the  question  while  reviewing  the  history  of  the 
general  geographical  development  of  the  region. 

Topography  of  Northern  New  Jersey.  The  topography  of 
northern  New  Jersey  may  be  briefly  described  as  made  up  of 
valleys  and  lowlands  that  have  been  etched  in  the  now  elevated 
surface  of  what  may  be  called  the  Schooley  peneplain  on  the 
Cretaceous  base-level.  The  topographical  atlas  of  New  Jersey 
should  be  constantly  referred  to,  in  order  to  follow  such  a  state- 
ment as  this ;  but  in  order  that  the  reader  may,  without  undue 
difficulty,  apprehend  the  meaning  of  my  descriptions  and  recog- 
nize the  various  localities  yet  to  be  named  without  the  trouble  of 
searching  for  them  on  the  maps  of  the  atlas,  I  have  attempted  to 
draw  a  generalized  bird's-eye  view  of  northern  New  Jersey  (Fig. 
37)  as  it  would  be  seen  by  an  observer  about  seventy  miles  verti- 
cally above  the  center  of  southern  New  Jersey.  The  meridians  are 
vertical,  and  east  and  west  lines  are  horizontal,  but  oblique  azi- 
muths are  foreshortened.  The  result  is  hardly  more  than  a  geo- 
graphical caricature,  and  I  publish  it  in  part  to  experiment  upon 
the  usefulness  of  so  imperfect  an  effort.  An  active  imagination 
may  perceive  the  long,  even  crest  line  of  Kittatinny  mountain  on 
the  northwest,  rising  beyond  the  rolling  floor  of  the  Kittatinny 
valley,  as  the  great  Allegheny  limestone  lowland  is  here  called ; 
then  come  the  highland  plateaus,  of  accordant  altitude  one  with 
another,  but  without  the  mesa-like  margin  that  my  pen  has  not 
known  how  to  avoid  indicating.  The  central  plain  lies  in  the 
foreground,  diversified  by  the  various  trap  ridges  that  rise  above 
its  surface  ;  First  and  Second  mountains  of  the  double  Watchung 
crescent  near  the  highlands ;  Sourland  mountain  in  the  south- 
west ;  and  Rocky  Hill,  the  southwestern  reappearance  of  the 
Palisade's  intrusive  trap  sheet,  lying  a  little  nearer  to  us.  The 
central  plain  is  also  diversified  by  the  fall  line,  a  slight  but 
rather  distinct  break  in  its  surface  from  Trenton  (7>.)  on  the 
Delaware  to  a  little  below  New  Brunswick  (NE]  on  the  Raritan. 
The  important  drainage  lines  are  :  the  Delaware,  forming  the 
western  boundary  of  the  state,  trenching  Kittatinny  mountain 
at  the  Water  Gap,  cutting  a  deep  transverse  valley  through  the 
highlands  where  it  receives  longitudinal  branches,  and  a  shal- 
lower trench  across  the  Kittatinny  lowland  and  the  central  plain ; 


490  PHYSIOGRAPHIC  ESSAYS 

the  Raritan,  whose  north  and  south  branches  head  in  the  high- 
lands, while  the  Millstone  joins  it  from  south  of  the  fall  line, 
cutting  through  Rocky  Hill  near  Princeton  (Pr.)  on  the  way ;  and 
the  Pequannock-Passaic,  rising  in  the  highlands,  gathering  tribu- 
taries in  the  low  basin  behind  the  Watchung  ridges,  and  escaping 
to  the  front  country  as  a  single  stream,  the  Passaic,  through  deep 
gaps  at  Paterson.  The  terminal  moraine,  marking  the  furthest 
advance  of  the  second  glacial  invasion  of  post-Tertiary  time,  is 
indicated  by  an  irregular  dotted  bank  crossing  the  state,  from 
the  Narrows  of  New  York  bay,  which  it  defines,  on  the  east, 
passing  over  Second  mountain  by  the  gap  at  Summit  (S),  rising 
midway  in  the  highlands  over  Schooley  mountain,  and  traversed 
by  the  Delaware  at  Belvidere  (B). 

The  Schooley  peneplain  is  indicated  by  the  crest  and  summit 
altitudes  of  Kittatinny  mountain,  the  highland  plateaus,  and  the 
trap  ridges.  This  peneplain  once  lay  low  and  essentially  hori- 
zontal, the  practically  completed  work  of  the  processes  of  denu- 
dation acting  on  a  previously  high  land  through  a  long  period  of 
time  ;  it  is  now  lifted  and  tilted  so  that  its  inland  portion  rises 
to  the  height  of  the  highlands,  which  are  its  remnants,  while  its 
seaward  portion  descends  slowly  beneath  a  cover  of  unconform- 
able  Cretaceous  beds,  southeast  of  the  fall  line,  and  thus  hidden 
sinks  gently  beneath  the  Atlantic  shore.  The  cover  of  Creta- 
ceous sediments  was  laid  on  the  southeastern  part  of  the  old 
peneplain  during  a  moderate  submergence  of  its  seaward  por- 
tion, before  the  elevation  and  tilting  above  mentioned  (Fig.  38). 
Much  of  the  cover  has  been  worn  away  since  the  time  of  eleva- 
tion (Figs.  39-42),  which  gave  opportunity  for  the  opening  of 
deep  valleys  on  the  soft  limestones  and  slates  among  the  hard 
crystalline  rocks  of  the  highlands ;  and  for  the  production  of 
the  broad  Kittatinny  valley  lowland  or  peneplain  on  the  wide 
belt  of  limestones  beyond  the  highlands ;  and,  furthermore,  for 
the  development  of  a  broad  base-leveled  plain  on  the  weak>  Tri- 
assic  shales  and  sandstones  where  the  old  peneplain  has  been 
almost  entirely  destroyed.  The  Cretaceous  cover  remains  only 
near  the  coast,  where  it  stood  too  low  to  be  attacked  while  the 
valleys  and  lowlands  just  described  were  carved  out.  An  inter- 
esting peculiarity  in  the  relation  between  the  newer  base-leveled 


492  PHYSIOGRAPHIC  ESSAYS 

plain  on  the  Triassic  area  and  the  old  Cretaceous  peneplain  is 
that  their  surfaces  mutually  intersect  at  a  small  angle  along  the 
line  which  now  marks  the  visible  contact  between  the  Triassic 
and  Cretaceous  formations:  the  newer  plain  standing  beneath  the 
eroded  portion  of  the  older  one  northwest  of  this  line,  while  it 
rises  above  the  buried  part  of  the  older  one  and  obliquely  trun- 
cates its  Cretaceous  cover  to  the  southeast  of  the  line.  Finally, 
the  land  as  a  whole  has  been  raised  a  little  since  the  making  of 
the  newer  plain,  and  shallow  valleys  interrupt  its  broad  surface.  It 
is  no  longer  a  true  plain  ;  it  has  become  a  pastplain.  A  few  words 
may  be  allowed  me  concerning  these  terms,  "peneplain"  and 
"  pastplain."  Given  sufficient  time  for  the  action  of  denuding 
forces  on  a  mass  of  land  standing  fixed  with  reference  to  a  con- 
stant base-level,  and  it  must  be  worn  down  so  low  and  so  smooth 
that  it  would  fully  deserve  the  name  of  plain.  But  it  is  very  un- 
usual for  a  mass  of  land  to  maintain  a  fixed  position  as  long  as 
is  here  assumed.  Many  instances  might  be  quoted  of  regions 
which  have  stood  still  so  long  that  their  surface  is  almost  reduced 
to  its  ultimate  form  ;  but  the  truly  ultimate  stage  is  seldom 
reached.  We  can  select  regions  in  which  the  valley  lowlands 
have  become  broad  and  flat,  the  intermediate  doab  hills  have 
wasted  away  lower  and  lower  until  they  are  reduced  to  forms  of 
insignificant  relief  ;  and  yet  the  surface  still  does  not  deserve 
the  name  of  plain  as  unqualifiedly  as  do  those  young  lands  newly 
born  from  seas  or  lakes  in  which  their  geometrically  level  sur- 
faces were  formed.  I  have  therefore  elsewhere  suggested  (430) 
that  an  old  region,  nearly  base-leveled,  should  be  called  an 
"  almost-plain,"  that  is,  a  peneplain. 

On  the  other  hand,  an  old  base-leveled  region,  either  a  pene- 
plain or  a  truly  ultimate  plain,  will,  when  thrown  by  elevation 
into  a  new  cycle  of  development,  depart  by  greater  and  greater 
degrees  from  its  simple  featureless  form,  as  young  narrow 
valleys  are  sunk  beneath  its  surface  by  its  revived  streams.  It 
therefore  no  longer  fully  deserves  the  name  that  was  properly 
applicable  before  its  elevation.  It  must  not  again  be  called  a 
peneplain,  for  it  is  now  not  approaching  and  almost  attaining  a 
smooth  surface,  but  is  becoming  rougher  and  rougher.  It  has 
passed  beyond  the  stage  of  minimum  relief,  and  this  significant 


THE  RIVERS  OF  NORTHERN  NEW  JERSEY         493 

fact  deserves  implication,  at  least,  in  a  name.  I  would  therefore 
call  such  a  region  a  pastplain.  The  area  of  the  weak  Triassic 
shales  was,  until  its  late  elevation,  as  good  an  example  of  an 
ultimate  base-leveled  plain  as  any  that  I  have  found  ;  but  now  it 
is  a  pastplain,  as  any  one  may  see  while  traveling  across  it  on 
the  train ;  its  doabs  are  broad  and  continuous  and  its  valleys  are 
relatively  narrow  and  shallow.  The  Kittatinriy  lowland  is  inter- 
sected by  streams  whose  valleys  sink  below  its  generally  even, 
gently  rolling  surface,  but  it  was  never  so  smooth  as  the  Triassic 
plain.  It  was  only  a  peneplain,  and  it  is  now  a  roughened 
peneplain.  Perhaps  the  more  adventurous  terminologist  will  call 
it  a  past-peneplain,  but  I  dare  not  venture  quite  so  far  as  that. 
When  the  highlands  were  lowlands,  their  surface  well  deserved 
the  name  of  peneplain,  but  they  were  lifted  so  long  ago  into  so 
high  a  position  that  they  are  now  cut  into  a  complicated  mass 
of  rugged  uplands.  They  no  longer  deserve  the  name  of  pene- 
plain;  and  if  in  preceding  paragraphs  I  have  referred  to  them 
as  constituting  an  old  peneplain,  it  is  because  no  satisfactory 
name  has  yet  been  applied  to  the  particular  stage  of  develop- 
ment of  plains  and  plateaus  in  which  they  now  stand. 

The  topography  of  northern  New  Jersey  is  therefore,  like  its 
structure,  polygenetic.  It  exhibits  very  clearly  a  series  of  forms 
developed  under  three  different  geographical  cycles,  and  closer 
search  will  doubtless  discover  forms  belonging  to  yet  other 
cycles,  less  complete  and  of  briefer  duration  than  these  three. 
There  is  the  tilted  and  deeply  eroded  peneplain  of  the  highlands, 
whose  initial  form  may  be  called  the  Schooley  peneplain,  from 
the  distinct  exhibition  of  one  of  its  remnants  on  Schooley's 
mountain ;  this  was  the  product  of  Jurassic  and  Cretaceous 
denudation.  There  is  the  younger  central  base-leveled  plain, 
developed  during  Tertiary  time,  or  thereabouts,  on  the  weaker 
Triassic  and  Cretaceous  beds ;  and  the  associated  valleys  of 
the  same  age  that  have  been  sunk  into  the  weakest  rocks  of  the 
highlands.  There  are  the  shallow  valleys  in  the  central  plain, 
of  the  latest  post-Tertiary  cycle,  requiring  the  name  of  this 
region  to  be  changed  from  plain,  as  it  was  lately,  to  pastplain, 
as  it  is  now.  The  first  cycle,  in  which  the  Schooley  peneplain 
was  produced,  witnessed  the  accomplishment  of  a  great  work ; 


494  PHYSIOGRAPHIC  ESSAYS 

it  included  in  its  later  part,  besides  various  other  oscillations,  the 
sub-cycle  when  the  seaward  or  southeastern  part  of  the  peneplain 
was  gently  submerged  and  buried  to  a  slight  depth  under  Creta- 
ceous deposits.  The  second  cycle  was  shorter,  being  a  time 
sufficient  to  base-level  the  softer  beds,  but  not  seriously  to  con- 
sume the  harder  parts  of  the  preexisting  surface.  We  are  still 
in  the  third  cycle,  of  which  but  a  small  part  has  elapsed.  The 
question  with  which  this  essay  opened  may  now  be  taken  up. 

Revived  and  Superimposed  Streams  in  New  Jersey.  The  streams 
and  rivers  of  northern  New  Jersey  may  be  examined  with  the 
intention  of  classifying  them  according  to  their  conditions  of  ori- 
gin, to  their  degree  of  complexity  as  indicated  by  the  number  of 
geographical  cycles  through  which  they  have  lived,  and  to  the 
advance  made  toward  their  mature  adjustment. 

The  Musconetcong  may  be  taken  as  the  type  of  the  highland 
streams.  It  flows  southwestward  along  a  narrow  limestone 
valley  between  crystalline  plateaus  on  either  side,  entering  the 
Delaware  a  little  below  Easton,  Pennsylvania  (E,  Fig.  37).  It 
drains  a  country  that  has  been  enormously  denuded,  and  during 
the  Jura-Cretaceous  cycle  of  this  deep  denudation  there  must 
have  been  time  for  it  and  its  fellows  to  become  thoroughly 
adjusted  to  the  structure  of  the  region ;  it  must  be  chiefly  for 
this  reason  that  it  flows  so  closely  along  the  weak  limestone  belt 
and  has  its  divides  close  by  on  the  adjoining  harder  crystallines 
(M,  Fig.  38).  Whatever  its  origin,  it  has  lost  every  initial  feature 
that  was  discordant  with  the  deep  structures  that  it  discovered 
beneath  the  initial  surface  ;  it  is  maturely  adjusted  to  its  environ- 
ment. It  endured  to  an  old  age  during  the  base-leveling  of  the 
Schooley  peneplain,  and  is  now  a  "  revived"  stream,  in  at  least 
its  second  cycle  of  work.  Most  of  the  other  streams  of  the 
highlands  and  the  country  farther  inland  are  also  of  this  well- 
adjusted,  revived  kind.  The  streams  of  the  Kittatinny  valley 
lowland  show  not  only  the  first  revival  of  the  kind  just  de- 
scribed, but  also  a  second  revival,  in  consequence  of  the  recent 
uplift  that  has  introduced  the  third  cycle  of  development, 
this  not  being  so  clearly  manifested  in  the  highlands,  where 
the  rocks  are  harder  and  the  valleys  of  the  second  cycle  are 
narrower. 


THE  RIVERS  OF  NORTHERN  NEW  JERSEY         495 

Look  now  at  the  drainage  of  the  crescentic  Watchung  moun- 
tains ;  the  curved  edges  of  two  great,  warped  lava  flows  of  the 
Triassic  belt.  The  noteworthy  feature  of  this  district  is  that 
the  small  streams  in  the  southern  part  of  the  crescent  rise  on  the 
back  slope  of  the  inner  mountain  and  cut  gaps  in  both  moun- 
tains i"n  order  to  reach  the  outer  part  of  the  central  plain.  If 
these  streams  were  descended  directly  or  by  revival  from  ances- 
tors, antecedent  to  or  consequent  upon  the  monoclinal  tilting  of 
the  Triassic  formation,  they  could  not  possibly,  in  the  long  time 
and  deep  denudation  that  the  region  has  endured,  have  main- 
tained, down  to  the  present  time,  courses  so  little  adjusted  to 


FIG.  38 

the  structure  of  their  basins.  In  so  long  a  time  as  has  elapsed 
since  the  tilting  of  the  Triassic  formation,  the  divides  would 
have  taken  their  places  on  the  crest  of  the  trap  ridges  and  not 
behind  the  crest  on  the  back  slope.  They  cannot  be  subsequent 
streams,  for  such  could  not  have  pushed  their  sources  headwards 
through  a  hard  trap  ridge.  Subsequent  streams  are  developed 
in  accordance  with  structural  details,  not  in  violation  of  them. 
Their  courses  must  have  been  taken  not  long  ago,  else  they  must 
surely  have  lost  their  heads  back  of  the  Second  mountain  ;  some 
piratical,  subsequent  branch  of  a  larger  transverse  stream,  like 
the  Passaic,  would  have  beheaded  them. 

The  only  method  now  known  by  which  these  several  doubly 
transverse  streams  could  have  been  established  in  the  not  too 
distant  past  is  by  superimposition  from  the  Cretaceous  cover 


496  PHYSIOGRAPHIC  ESSAYS 

that  was  laid  upon  the  old  Schooley  peneplain.  It  has  already 
been  stated  that  when  the  highlands  and  this  region  together 
had  been  nearly  base-leveled,  the  coastal  portion  of  the  result- 
ing peneplain  was  submerged  and  buried  by  an  unconformable 
cover  of  waste  derived  from  the  non-submerged  portion  ;  hence, 
when  the  whole  area  was  lifted  to  something  like  its  present 
height,  a  new  system  of  consequent  streams  was  born  on  the 
revealed  sea-bottom.  Since  then,  time  enough  may  have  passed 
to  allow  the  streams  to  sink  their  channels  through  the  uncon- 
formable cover  and  strip  it  off,  and  thus  superimpose  themselves 
ofi  the  Triassic  rocks  below ;  we  should  therefore  find  them,  in 
so  far  as  they  have  not  yet  been  readjusted,  following  inconse- 
quent, discordant  courses  under  formation.  The  existing  overlap 
of  the  Cretaceous  beds  on  the  still  buried  Triassic  portion  of  the 
old  Schooley  peneplain  makes  it  evident  that  such  an  origin  for 
the  Watchung  streams  is  possible  ;  but  it  has  not  yet  been  inde- 
pendently proved  that  the  Cretaceous  cover  ever  reached  so  far 
inland  as  to  cross  the  Watchung  ridges. 

Want  of  other  explanation  for  the  Watchung  streams  is  not 
satisfactory  evidence  in  favor  of  the  explanation  here  suggested. 
There  should  be  external  evidence  that  the  Triassic  area  has 
actually  been  submerged  and  buried  after  it  was  base-leveled  to 
the  Schooley  peneplain  and  before  it  was  uplifted  to  its  present 
altitude ;  other  streams  as  well  as  the  ones  thus  far  indicated, 
should  bear  signs  of  superimposition ;  and  if  adjustment  of  the 
superimposed  courses  has  begun,  it  should  be  systematically 
carried  farthest  near  the  largest  streams.  I  shall  not  here  state 
more  than  in  brief  form  the  sufficient  evidence  that  can  be 
quoted  in  favor  of  the  first  and  second  requisites.  Suffice  it  to 
say,  that  the  overlap  of  the  Cretaceous  beds  (which  contain  prac- 
tically no  Triassic  fragments)  on  the  beveled  Triassic  strata  at 
Amboy  and  elsewhere  indicates  submergence  after  base-leveling; 
and  that  the  pebbles,  sands,  and  marls  of  the  Cretaceous  series 
point  clearly  to  the  highlands  as  their  source.  The  submergence 
must  therefore  have  reached  inland  across  the  Triassic  formation 
at  least  to  the  margin  of  the  crystalline  rocks.  Some  shore -line 
cutting  must  have  been  done  at  the  margin  of  the  highlands 
during  Cretaceous  time,  but  the  generally  rolling  surface  of  the 


THE  RIVERS  OF  NORTHERN   NEW  JERSEY          497 

old  peneplain  leads  me  to  ascribe  its  origin  chiefly  to  sub-aerial 
wasting.  Moreover,  the  North  Branch  of  the  Raritan,  between 
Mendham  and  Peapack  (*  Fig.  37)  and  the  Lockatong  (Z),  a 
small  branch  of  the  Delaware,  on  the  West  Hunterdon  sand- 
stone plateau,  give  striking  indications  of  superimposition  in  the 
discordance  of  their  courses  with  the  weaker  structural  lines  of 
their  basins,  so  unlike  the  thoroughly  adjusted  course  of  the 
Musconetcong  and  its  fellows,  the  Pohatcong,  the  Lopatcong, 
and  others. 

Growth  of  Subsequent  Streams.  The  third  requisite  of  the 
proof  of  the  inland  extension  of  the  Cretaceous  and  the  result- 
ing superimposed  origin  of  the  Watchung  streams  may  be  stated 


FIG.  39 

in  detail,  as  being  more  in  the  line  of  this  essay :  has  the  adjust- 
ment that  accompanies  superimposition  systematically  advanced 
farther  near  the  large  streams  than  near  the  small  ones  ?  The 
character  of  this  adjustment  should  be  first  examined  deduct- 
ively. Given  a  series  of  streams  of  different  volumes,  flowing 
southeastward,  in  the  direction  of  the  present  dip  of  the  remnant 
of  the  Cretaceous  cover,  over  the  former  inland  extension  of 
this  superposed  formation,  how  will  these  streams  react  on 
one  another  when  they  sink  their  channels  into  the  underlying 
Triassic  formation  ? 

The  conditions  during  the  formation  of  the  cover  of  Cre- 
taceous beds  are  illustrated  in  Fig.  38,  where  the  Triassic  por- 
tion of  the  peneplain  is  submerged  and  the  shore-line  of  the 


498 


PHYSIOGRAPHIC  ESSAYS 


transgressing  ocean  has  reached  the  margin  of  the  crystalline 
rocks.  The  waste  from  the  crystallines  is  spread  out  as  a  series 
of  gravels,  sands,  and  marls  on  the  base-leveled  Triassic  area. 


FIG.  40 

Then  follows  the  elevation  and  tilting  of  the  peneplain  with 
the  cover  on  its  back  ;  and  with  this  regression  of  the  sea  there 
is  an  equivalent  gain  of  new  land  ;  a  smooth,  gently  sloping  plain 
is  revealed  as  the  shore-line  retreats  ;  streams  run  out  across  it 
from  the  crystalline  area,  or  begin  on  its  open  surface,  growing 
mouthward  as  the  land  rises.  Three  such  streams,  A,  C,  D,  are 


FIG.  41 

shown  in  Fig.  39 ;  their  opportunity  for  deep  valley  cutting  is 
indicated  by  the  depth  of  the  new  base-level,  BL,  below  the  gen- 
eral surface  of  the  country.  While  these  streams  are  deepening 
their  channels  in  the  Cretaceous  cover,  which  is  unshaded  with 


THE  RIVERS  OF  NORTHERN  NEW  JERSEY          499 

marginal  contour  lines  in  the  figures,  their  subsequent  auto- 
genetic  branches  are  irregularly  disposed,  because  there  is  no 
lateral  variation  of  structure  to  guide  them  ;  but  after  a  time  the 


FIG.  42 

base-leveled  surface  of  the  buried  Triassic  beds  is  reached,  as  is 
shown  by  linear  shading  in  the  valley  bottoms  of  Figs.  40-43. 
The  growth  of  the  subsequent  branches  then  developed  will  be 
along  the  strike  of  the  Triassic  softer  beds,  that  is,  about  square 
to  the  course  of  the  three  transverse  streams  under  consider- 
ation. The  most  rapid  growth  will  be  found  on  the  branches 


FIG.  43 

of  the  largest  stream,  A,  because  it  will  most  quickly  cut  down 
its  channel  close  to  the  base-level  of  the  time  and  thus  provide 
steep,  sloping  valley  sides,  from  which  the  subsequent  branches 
cut  backwards  most  energetically.  In  due  time  the  main  streams 


500  PHYSIOGRAPHIC  ESSAYS 

discover  the  particularly  resistant  transverse  lava  sheets  in  the 
underlying  formation,  and  then  the  subsequent  branches  of  the 
largest  transverse  stream  on  the  upstream  side  of  the  obstruc- 
tions, for  example,  ^and  G  (Fig.  40),  will  have  a  great  advantage 
over  those  of  the  smaller  streams.  The  most  rapidly  growing 
subsequent  branch,  G  (Fig.  41),  of  the  largest  transverse  master 
stream,  A,  may  grow  head  wards  so  fast  as  to  push  away  the 
divide,  X,  which  separates  it  from  the  head  of  the  opposing  sub- 
sequent branch,/,  of  the  next  adjacent  smaller  transverse  stream, 
C,  and  thus  finally  to  capture  and  divert  the  headwaters,  H,  of 
the  smaller  transverse  stream  to  the  larger  one,  as  in  Fig.  42. 
The  divide  creeps  while  the  two  opposing  subsequent  branches 
are  in  contest ;  it  leaps  when  the  successful  subsequent  branch 
reaches  the  channel  of  the  conquered  stream.  The  first  stream 
captured  in  this  way  must  necessarily  be  the  nearest  to  the  large 
stream.  The  diversion  of  the  considerable  volume~of  headwaters, 
H,  to  the  channel  of  the  small  subsequent  branch,  G,  causes  it 
to  deepen  its  channel  rapidly ;  the  same  effect  is  perceptible  in 
H  for  a  distance  above  its  point  of  capture  and  diversion ;  the 
increased  load  of  sediment  thus  given  to  G  will  be  in  great  part 
dropped  in  a  fan  delta,  where  it  enters  the  flat  valley  of  the 
master  stream  (Fig.  42). 

Gaining  strength  by  conquest,  other  captures  are  made,  faster 
for  a  time,  but  with  decreasing  slowness  as  the  head  of  the 
diverting  subsequent  branch  recedes  from  the  original  master ; 
and  at  last,  equilibrium  may  be  gained  when  the  headwater 
slope  of  the  diverting  branch  is  no  greater  than  that  of  the 
opposing  subsequent  branch  of  the  next  uncaptured  transverse 
stream.  After  the  capture  of  a  transverse  stream  has  been 
effected  in  this  way,  the  divide,  y,  between  its  diverted  upper 
portions,  ^(Fig.  42),  and  its  beheaded  lower  portion,  C,  will  be 
pushed  downstream  by  the  growth  of  an  inverted  stream,  V. 
This  goes  on  until  the  equilibrium  is  attained,  and  further  shift- 
ing is  prevented  on  reaching  the  hard,  transverse  lava  sheets,  Z 
(Fig.  43) ;  here  the  divide  is  maturely  established.  In  the  case  of 
a  system  of  transverse  streams,  C,  D,  etc.  (Fig.  43),  successively 
captured  by  the  subsequent  branch  of  a  single  master,  the  di- 
vides, Z,  y',  between  the  inverted  (V,  V')  and  beheaded  (C,  D) 


THE  RIVERS  OF  NORTHERN  NEW  JERSEY          501 

portions  of  the  captured  streams  will  for  a  time  present  different 
stages  of  approach  to  establishment.  The  divide  on  the  line  of 
that  one  of  the  original  streams,  C,  that  is  nearest  to  the  master 
stream,  A,  may  reach  a  final  stable  position,  Z\  while  on  the 
next  stream,  farther  away  from  the  master,  the  beheaded  portion, 
Z>,  may  still  retain  a  short  piece  above  the  gap  in  the  upper  lava 
sheet,  not  yet  secured  by  the  inverted  stream,  V1 ,  and  a  third 
stream,  farther  away  still  from  the  master  (not  shown  in  Fig.  43), 
might  remain  uncaptured  -and  independent. 

It  is  by  such  tests  as  these  that  we  may  hope  to  recognize  the 
occurrence  of  partial  adjustment  in  the  streams  of  the  Watchung 
crescent  as  a  result  of  their  superimposition  on  the  Triassic 
formation  from  its  former  Cretaceous  cover.  The  greater  the 
degree  of  complexity  in  the  tests  proposed,  the  more  confidence 
we  shall  have  in  the  theory  when  the  tests  successfully  meet  the 
facts.  Hence  the  reason  for  deductively  carrying  out  the  theo- 
retical conditions  to  their  extremest  consequences  in  order  to 
increase  the  complexity  of  the  tests  that  are  to  be  confronted 
with  the  facts.  This,  as  a  matter  of  method,  seems  to  be  of 
great  practical  importance  in  any  attempt  to  decipher  the  past 
progress  of  geographical  development. 

The  admirable  contoured  topographical  maps  of  New  Jersey, 
issued  by  the  Geological  Survey  of  that  State  under  the  leader- 
ship of  the  late  Professor  George  H.  Cook,  afforded  means  of 
applying  the  deductive  tests  above  outlined  without  the  neces- 
sity of  plodding  over  all  the  country  concerned  ;  but  however 
good  the  maps  are,  it  is  hardly  necessary  to  say  that  they  can 
be  interpreted  with  a  better  appreciation  of  the  facts  that  they 
represent  after  an  excursion  on  the  ground  has  given  the  student- 
some  personal  acquaintance  with  it.  This  I  have  tried  to  gain 
on  various  occasions,  maps  in  hand. 

Atlas  sheet  number  six,  including  the  central  red-sandstone 
area  and  the  five-mile-to-an-inch  geological  map  of  the  state, 
presents  in  the  clearest  manner  the  facts  of  form  and  structure 
involved  in  our  problem ;  and  to  my  mind  the  correspondence 
between  theory  and  fact  is  very  striking.  The  Pequannock- 
Passaic  is  the  master  transverse  stream  of  the  region ;  its  pre- 
eminence was  probably  due  in  the  beginning  to  its  gathering, 


502  PHYSIOGRAPHIC  ESSAYS 

from  the  unsubmerged  highlands,  a  greater  amount  of  drainage 
than  belonged  to  any  other  stream  that  ran  southeastward  down 
the  gentle  slope  of  the  newly  revealed  Cretaceous  cover.  It  was 
at  that  time  a  compound,  composite  river :  compound,  because 
it  drained  areas  of  different  ages ;  composite,  because  these 
areas  were  of  different  structures.  Existing  examples  of  com- 
pound, composite  rivers  are  seen  in  the  Catawba,  the  Yadkin- 
Pedee,  the  Cape  Fear,  and  the  Neuse  rivers  of  North  Carolina, 
which  all  rise  on  the  inland  crystalline  area  and  traverse  the 
coastal  quaternary  plain  before  reaching  the  sea.  But  unlike 
these,  there  must  have  been,  when  the  old  submerged  land  rose 
with  the  Cretaceous  cover  on  its  back,  numerous  small  streams 
whose  drainage  area  lay  entirely  within  the  Cretaceous  plain. 
These  were  simple  streams,  flowing  over  a  structure  of  one 
kind  and  one  age.  Their  modern  homologues  are  seen  in  the 
Maurice,  the  Great  and  Little  Egg  Harbor,  and  the  Wading 
rivers  of  southern  New  Jersey,  and  I  suppose  also  in  various 
relatively  short  streams  of  North  Carolina,  such  as  the  Lumber, 
Great  Cohera,  and  Mocassin. 

It  cannot  be  supposed  that  the  original  Pequannock-Passaic 
possessed  the  large  southern  branch,  which  I  shall  call  the  upper 
Passaic,  by  which  Great  Swamp  is  now  drained  ;  for  had  this 
been  the  case,  the  divides  between  the  branches  of  the  upper 
Passaic  and  the  heads  of  the  small  streams  that  now  still  cross 
both  of  the  trap  ridges  must  long  ago  have  been  driven  to  a 
stable  position  on  the  crest  line  of  the  inner  ridge.  It  should 
be  recognized  that  the  present  roundabout  drainage  of  the  Great 
Swamp  is  a  post-glacial  feature,  determined  by  the  morainic  bar- 
rier that  crosses  the  basin  from  Summit,  S,  to  Morristown,  M\ 
the  pre-glacial  drainage  of  the  southern  part  of  the  inner  crescent 
was  undoubtedly  of  a  simpler  and  more  direct  pattern.  The 
upper  Passaic  member  of  the  Pequannock-Passaic  system  must 
be  regarded  as  a  branch  of  subsequent  development,  guided  by 
some  of  the  softer  Triassic  beds  when  they  were  reached  be- 
neath the  Cretaceous  cover,  and  very  successful  in  capturing  and 
diverting  other  transverse  streams  that  were  smaller  than  its 
master.  For  some  distance  on  either  side  from  the  Pequannock- 
Passaic  gap  in  the  trap  ridges  at  Paterson,  the  existing  streams 


THE  RIVERS  OF  NORTHERN  NEW  JERSEY          503 

are  perfectly  adjusted  to  the  Triassic  structure  ;  that  is,  the 
ridges  are  persistent  divides,  and  the  lateral  subsequent  branches 
of  the  master  flow  along  the  strike  of  the  softer  shales  and  sand- 
stones, except  where  lately  thrown  off  their  courses  by  glacial 
drift  barriers.  This  I  interpret  as  meaning  that  the  Pequannock- 
Passaic  master  stream  hereabouts  made  so  early  a  capture  of 
adjacent  superimposed  streams  that  all  traces  of  their  initial 
discordant  courses  have  been  obliterated  by  the  development  of 
structurally  accordant  subsequent  streams. 

The  Watchung  ridges  extend  only  about  eight  miles  northward 
of  the  Paterson  gaps,  but  reach  thirty  miles  southwestward.  It 
is  therefore  chiefly  in  the  latter  direction  that  we  may  expect  to 
find  examples  of  incomplete  adjustment  following  superimposition 
and  capture.  At  Milburn  there  is  a  deep  gap  in  First  mountain, 
and  opposite  this,  at  Summit  S  (Fig.  37),  a  partly  drift-filled  gap 
in  Second  mountain ;  this  I  am  disposed  to  regard  as  the  former 
outlet  of  the  Rockaway-Rahway  river,  which  on  account  of  its 
considerable  size  was  not  captured  by  the  Passaic  until  it  had  cut 
its  passage  across  the  trap  sheets  almost  to  a  safe  depth.  The 
diverted  upper  portion — the  Rockaway — now  joins  the  Passaic, 
its  crooked  course  from  the  highlands  via  Boonton  (Bti)  being  a 
post-glacial  irregularity  ;  the  beheaded  lower  portion  —  the  Rah- 
way  —  heads  on  the  ridge  of  Second  mountain,  retains  the  pair 
of  subsequent  streams  between  the  two  ridges,  and  flows  in 
diminished  volume  to  the  sea,  the  divide  between  the  two  por- 
tions being  in  its  mature  stable  position  on  Second  mountain. 

South  of  the  Milburn  gap  there  are  three  streams  that  main- 
tain water  gaps  in  First  mountain,  and  five  head  branches  of 
these  three  streams  rise  behind  the  crest  of  Second  mountain. 
These  must  be  interpreted  as  remnants  of  streams  that  once  rose 
further  inland  and  whose  upper  courses  have  been  captured  by 
the  victorious  upper  Passaic  ;  but  it  is  noteworthy  that  here,  at 
the  greatest  distance  from  the  gap  of  the  master  stream  at 
Paterson,  the  divides  between  the  diverted  and  beheaded  por- 
tions of  these  southern  streams  should  lie  in  unstable  positions 
back  of  the  crest  line  of  Second  mountain.  This  is  exactly  what 
the  hypothesis  of  a  superimposed  origin  for  these  streams  would 
require  ;  and  if  the  complexity  of  accordance  between  deduction 


504  PHYSIOGRAPHIC  ESSAYS 

and  fact  here  presented  be  duly  considered,  I  believe  new  confi- 
dence may  be  gained  in  the  hypothesis  of  superimposition,  already 
rendered  likely  from  other  evidence.  u/on^C  fl ?/ ,1 -..-.•  r +. 

The  rectangular  courses  of  the  streams  that  cross  First  and 
Second  mountains  southwest  of  Milburn  do  not  militate  against 
their  initial  obliquely  superimposed  courses ;  for,  as  Gilbert  has 
shown,  oblique  courses  across  tilted  beds,  alternately  hard  and 
soft,  will  gradually  shift  until  they  follow  rectangular  courses 
along  the  strike  of  the  soft  beds  and  square  across  the  strike  of 
the  hard  beds.  Middle  Brook,  at  the  southern  bend  of  First 
mountain,  near  Bound  Brook  (BB},  presents  the  peculiarity  of 
branching  east  and  west  while  on  the  trap  sheet  of  the  moun- 
tain. This  may  be  due  to  a  retention  here,  where  the  dip  is 
moderate,  of  an  initially  superimposed  bifurcation,  or  to  guid- 
ance by  fractures  at  this  point  where  the  course  of  the  mountain 
changes  rather  abruptly  ;  the  facts  at  hand  do  not  serve  to  make 
choice  between  these  alternatives. 

Green  River  in  the  Uinta  Mountains.  The  lesson  of  greatest 
importance  in  this  study  lies,  to  my  mind,  in  the  gradual  devel- 
opment of  accordant  subsequent  streams  in  a  region  where  the 
unchanged  superimposed  drainage  would  show  no  such  accord- 
ance. Similar  adjustment  of  subsequent  streams  to  structural 
features  may  characterize  drainage  systems  that  were  originally 
antecedent ;  and  with  this  principle  in  mind  I  have  recently 
read  over  with  renewed  interest  Powell's  classic  study  of  the 
Green  river  where  it  crosses  the  Uinta  mountains  (a,  152-166). 
(See  also  the  geological  map  in  the  "  Geology  of  the  Uinta  Moun- 
tains.") The  Green  river  and  the  smaller  streams  of  its  lateral 
canons  and  valleys  are  all  regarded  as  antecedent.  Let  us  ex- 
amine the  arguments  on  which  this  conclusion  rests. 

The  Green  river  itself  rises  many  miles  north  of  the  Uinta 
range,  traverses  a  relatively  low  basin  before  reaching  the  flank 
of  the  mountains,  and  then  instead  of  turning  away,  it  boldly 
enters  the  great  uplift  and  trenches  it  from  side  to  side  in  a 
profound  canon,  flowing  out  to  the  southwest  on  its  way  to  the 
Colorado.  There  is  relatively  low  ground  at  the  eastern  end  of 
the  range,  several  thousand  feet  lower  than  the  summits  of  the 
range  on  either  side  of  the  Green  river  canon,  and  many 


THE  RIVERS  OF  NORTHERN   NEW  JERSEY          505 

thousand  feet  lower  than  the  restored  crest  of  the  great  uplift ; 
but  the  river  does  not  follow  this  open  roundabout  course.  Powell 
says  that  the  river  cut  through,  instead  of  running  around,  the 
great  obstruction,  because  it  "  had  the  right  of  way ;  .  .  .  it  was 
running  ere  the  mountains  were  formed."  Had  the  mountain 
fold  been  formed  suddenly,  it  would  have  turned  the  river  around 
it  to  the  east ;  "  but  the  emergence  of  the  fold  above  the  general 
surface  of  the  country  was  little  or  no  faster  than  the  progress 
of  the  corrasion  of  the  channel.  .  .  .  The  river  preserved  its 
level,  but  the  mountains  were  lifted  up.  .  .  .  The  river  was  the 
saw  which  cut  the  mountains  in  two  "  (a,  152,  153).  If  this  inter- 
pretation is  correct,  the  Green  river  would  be  the  type  of  a  per- 
fect antecedent  stream,  but  it  appears  to  me  that  the  case  is 
probably  overstated  in  that  respect.  Perhaps  it  would  have  been 
more  deliberately  stated  in  a  later  volume  if  Powell's  intention 
of  describing  more  fully  the  three  chief  kinds  of  drainage  of  the 
region  had  been  carried  out  (£,  v).  Not  having  seen  the  region, 
my  comments  may  have  little  value  ;  but  the  context  of  Powell's 
report,  the  description  'of  the  immense  series  of  lacustrine  beds, 
over  a  mile  thick,  north  of  the  mountains,  and  the  eastward  de- 
flection of  the  river  where  it  traverses  the  mountains,  all  seem 
to  me  to  indicate  that  the  Green  was  by  no  means  continuously 
successful  in  maintaining  its  antecedent  course  across  the  uplift. 
It  is  by  no  means  a  typical  antecedent  river.  The  great  series 
of  lacustrine  beds  upstream  from  the  canon,  with  conglomerates 
where  they  rest  on  the  northern  flank  of  the  mountains,  are  fully 
recognized  in  the  report,  and  must  mean  that  the  upper  portion 
of  the  river  was  for  a  time  shut  back,  or  ponded.  During  part  of 
this  time  there  may  have  been  no  overflow  across  the  growing 
mountains,  for  the  lower  lacustrine  beds  contain  fossils  indicative 
of  brackish  water  (£,  84,  Chap.  Ill,  by  C.  A.  White).  The  intermit- 
tent growth  of  the  mountains  and  the  repeated  return  of  lacustrine 
conditions,  with  gradually  freshening  water,  is  indicated  by  the 
strong  unconformities  that  occur  at  various  points  in  the  lacus- 
trine beds,  and  by  the  change  in  the  fossil  fauna.  It  must  be 
conceded  from  this  that 'the  upper  portion  of  Green  river  was 
repeatedly  ponded  back  by  mountain  growth  across  its  middle 
course ;  we  therefore  have  not  now  any  close  indication  of  its 


506  PHYSIOGRAPHIC  ESSAYS 

pre-lacustrine  course  above  the  mountains  ;  the  ancient,  or  pre- 
Uinta,  upper  portion  of  the  river  was  extinguished  by  the  lacus- 
trine sediments,  and  to  that  extent  the  Green  river  departs  from 
the  perfect  antecedent  type. 

In  the  second  place,  if  the  original  Green  river  existed  upon 
the  upper  surface  of  the  beds  that  were  at  a  subsequent  date 
raised  to  form  the  Uinta  uplift,  it  does  not  appear  to  be  clearly 
proved  that  its  course  at  that  early  time  was  closely  coincident 
with  its  present  course  in  the  mountainous  area.  The  first  def- 
ormations of  the  mountain  growth  may  have  temporarily  inter- 
rupted its  flow,  as  is  made  likely  by  the  lacustrine  deposits  already 
referred  to ;  and  when  the  rise  in  the  level  of  the  waters  of  the 
lake  overtook  the  uplift,  probably  at  a  time  of  slower  mountain 
growth  than  that  which  first  formed  the  lake,  the  point  of  over- 
flow may  have  been  many  miles  to  one  side  of  its  previous 
drowned-out  course.  The  moderate  elevation  of  the  eastern  end 
of  the  range,  where  it  connects  with  the  Yampa  plateau,  may 
possibly  have  then  been  a  little  higher  than  a  point  farther  west, 
where  the  overflow  was  consequently  located.  This  is  perhaps 
hardly  as  probable  as  the  postulates  involved  in  arguing  a  truly 
antecedent  course  for  the  river ;  but  its  impossibility  is  not  as 
strictly  proved  as  would  be  necessary  before  a  definite  conclusion 
as  to  the  continuous  persistence  of  an  antecedent  river  could  be 
finally  accepted.  Such  continuity  of  action  must  be  rare  and 
should  be  rigorously  demonstrated  if  possible. 

It  must,  moreover,  be  remembered  that  Emmons  is  of  the  opin- 
ion that  the  Colorado  river  is  not  antecedent  at  all,  but  is  super- 
imposed on  the  eastern  portion  of  the  Uinta  range  from  a  course 
that  it  had  chosen  upon  a  sheet  of  horizontal  sediments  —  the 
Wyoming  conglomerate  —  which  he  supposes  once  stretched 
unconformably  all  over  the  previously  deeply  eroded  surface  of 
the  uplifted  range,  where  the  canon  is  now  cut.  He  quotes 
facts  of  two  kinds  in  evidence  of  this  :  first,  the  remnants  of  the 
Wyoming  conglomerate  still  lie  on  ridges  as  high  as  those  that 
inclose  the  river  canons ;  second,  the  Green  and  certain  of  its 
branches  possess  tortuous  courses,  out'  of  accord  with  the  struc- 
ture of  the  range.  It  might  be  added  that  the  wide,  open  valley 
of  Brown's  park  in  the  middle  of  the  range  is  best  explained  as 


THE  RIVERS  OF  NORTHERN  NEW  JERSEY          507 

the  product  of  a  pre -Wyoming  cycle  of  erosion  by  rivers  that 
were  extinguished  when  the  Wyoming  beds  were  laid  over  the 
mountains.  The  strongest  objection  to  Emmons's  conclusion 
seems  to  be  the  great  amount  of  erosion  that  it  requires ;  ero- 
sion sufficient  not  only  to  remove  the  Wyoming  conglomerate 
from  nearly  all  its  former  overlap  on  the  Uinta  range,  where  it 
had  buried  and  extinguished  a  pre- Wyoming  drainage,  but  also 
to  carry  away  a  vast  extension  of  the  formation  at  the  same 
height,  north  of  the  range.  It  may  be  best  to  conclude  that 
both  antecedent  and  superimposed  processes  must  be  called  on ; 
for  one  must  hesitate  before  admitting  that  the  Wyoming  beds 
stretched  all  across  the  country  north  and  east  of  the  Uinta 
range  up  to  the  height  at  which  the  remnants  are  now  found  on 
the  range ;  it  seems  more  likely  that  some  part  of  the  height  of 
these  remnants  is  due  to  a  relatively  local  elevation.  As  far  as 
this  is  the  case,  it  gives  reason  for  regarding  the  Green  as  an 
antecedent  river ;  that  is,  antecedent  to  the  local  elevation  of 
the  Wyoming  beds,  but  long  posterior  to  the  elevation  of  the 
Uinta  range ;  but  as  the  river  now  flows  —  according  to  Em- 
mons's theory  —  on  beds  lying  unconformably  below  those  on 
which  its  course  was  chosen,  it  is  for  this  reason  to  be  classed 
as  superimposed. 

The  Green  river,  therefore,  certainly  departs  from  the  type  of 
an  antecedent  stream  ;  the  departure  is  distinct  in  its  repeated 
ponding,  whereby  its  upper  course  was  broadly  and  indetermi- 
nately shifted  from  its  original  location ;  and  is  at  least  possible, 
if  not  probable,  in  its  defeat  at  the  line  of  uplift  and  subse- 
quent superimposition  on  a  new  line  of  overflow.  The  mountains 
wrenched  the  saw  that  afterwards  cut  them  in  two. 

A  study  of  the  Jura  drainage,  of  which  a  fuller  account  may 
be  given  at  some  future  time,  has  led  to  the  provisional  conclu- 
sion that  many  of  its  streams  show  a  combination  of  consequent 
and  antecedent  characteristics.  They  appear  to  be  consequent 
on  the  early  stages  of  the  deformation,  but  antecedent  to  its 
later  growth,  and  for  this  kind  of  a  stream  I  have  no  satisfactory 
name  to  suggest  at  present. 

Heim  has  shown  that  the  Reuss  and  the  adjacent  smaller 
transverse  streams  of  northern  Switzerland  near  Lucerne  are 


508  PHYSIOGRAPHIC  ESSAYS 

in  part  persistent  across  a  series  of  folds,  and  in  part  slightly 
shifted  from  one  course  to  another  and  ponded  in  Lake  Lucerne  ; 
but  unless  the  other  ranges  of  the  Alps  rise  hereafter  faster 
than  they  have  heretofore,  the  geologist  of  the  future  will  reason- 
ably regard  the  more  mature  Reuss  as  an  essentially  successful 
antecedent  river. 

The  Sutlej  and  other  rivers  that  escape  from  the  inner  valleys 
of  the  Himalaya  by  deep  gaps  in  the  outer  ranges  are  described 
by  Medlicott  as  antecedent  to  the  elevation  of  the  ranges  through 
which  they  flow,  their  antecedent  origin  being  argued  from  the 
delta-like  structure  of  the  upturned  beds  in  the  outer  gorges, 
as  if  the  rivers  were  now  cutting  down  the  deformed  deltas  of 
an  earlier  time ;  but  the  heavy  gravel  and  sand  deposits  in  their 
upper  valleys  indicate  that  they  were  nearly,  if  not  quite,  ponded 
for  a  time  during  the  deformation. 

Rivers  seem  to  have  the  habit  of  cutting  down  their  upturned 
deltas.  Bonney  refers  to  several  such  examples  among  the  riv- 
ers that  flow  northward  from  the  Alps  and  transect  particularly 
thick  portions  of  the  upturned  marginal  conglomerates  and 
sandstones,  which  he  regards  as  the  deltas  formed  by  the  same 
rivers  at  an  earlier  time,  when  the  mountain  folding  had  not  ex- 
tended outward  as  far  as  it  does  now  from  the  axis  of  the  Alps. 
I  have  suspected  that  the  same  kind  of  evidence  might  be  used 
to  indicate  that  the  Delaware  above  Trenton,  between  Pennsyl- 
vania and  New  Jersey,  is  in  part  even  of  pre-Triassic  origin, 
for  where  it  now  enters  the  Triassic  belt  there  is  a  particularly 
heavy  and  coarse  sandstone,  sometimes  conglomeratic.  Being  a 
large  stream,  it  might  persist  in  an  anaclinal  course  through  the 
northwestward  monocline  formed  by  the  Jurassic  uplift  of  the 
Triassic  beds,  although  the  smaller  streams  of  the  region  were 
then  probably  extinguished,  to  be  replaced  by  a  new  system  con- 
sequent upon  the  new  order  of  things. 

Large  rivers,  more  or  less  persistent  in  the  face  of  opposing 
disturbance,  therefore  appear  to  be  generally  recognized ;  but  it 
is  noticeable  that  those  quoted  from  the  Himalaya  and  the  Alps 
presumably  occupied,  at  the  time  of  disturbance,  well-inclosed 
valleys,  from  which  it  would  have  been  difficult  for  them  to 
escape  backwards  or  laterally ;  and  that,  even  if  successful  in 


THE  RIVERS  OF  NORTHERN   NEW  JERSEY         509 

the  end,  they  for  a  time  suffered  defeat  or  ponding  of  greater  or 
less  extent  and  duration.  There  is  no  evidence  that  the  Green 
river  was  well  inclosed  immediately  north  of  the  Uinta  moun- 
tains at  the  time  of  their  first  elevation ;  hence  the  likelihood 
of  its  temporary  ponding  or  inclosure  is  increased. 

It  is  stated  by  Powell  that  not  only  the  Green  but  even  the 
smaller  streams  of  the  Uintas  are  of  origin  antecedent  to  the 
mountains.  He  writes  : 

The  explanation  of  the  canons  of  Green  river  will  assist  us  in  understand- 
ing the  origin  of  the  lateral  valleys  and  canons.  The  streams  were  there 
before  the  mountains  were  made;  that  is,  the  streams  carved  out  the  val- 
leys and  left  the  mountains.  The  direction  of  the  streams  is  indisputable 
evidence  that  the  elevation  of  the  fold  was  so  slow  as  not  to  divert  the 
streams,  although  the  total  amount  of  elevation  was  many  thousands  of  feet. 
Had  the  fold  been  lifted  more  rapidly  than  the  principal  streams  could 
have  cut  their  channels,  Green  river  would  have  been  turned  about  it,  and 
all  the  smaller  streams  and  water  ways  would  have  been  cataclinal  (#,  162). 

This  appears  to  me  an  unproved  conclusion,  and  the  evidence 
of  it  needs  careful  attention.  It  appears  that  there  are  several 
streams  which  descend  from  the  crest  of  the  mountains  towards 
the  flanks,  but  instead  of  running  all  the  way  out  to  the  margin 
of  the  fold,  they  turn  along  the  strike  of  a  monoclinal  valley,  and 
thus  reach  the  main  river  by  a  short  cut.  Such  streams  are  cata- 
clinal for  a  time,  then  monoclinal.  It  is  in  reference  to  these 
that  it  is  said,  "  the  streams  were  there  before  the  mountains 
were  made";  and  again,  "  the  drainage  was  established  ante- 
cedent to  the  corrugation  or  displacement  of  the  beds  by  fault- 
ing and  folding"  (a,  163).  In  approaching  this  conclusion 
Powell  says  that  these  streams  cannot  be  consequent,  for 

valleys  consequent  upon  the  corrugation,  which  was  one  of  the  conditions 
of  the  origin  of  the  Uinta  mountains,  could  not  have  taken  the  direction 
observed  in  this  system  ;  they  would  have  all  been  cataclinal,  as  they  ran 
down  from  the  mountains,  and  turned  into  synclinal  valleys  at  the  foot, 
forming  a  very  different  system  from  that  which  now  obtains  (#,  166). 

Nor  can  the  streams  be  superimposed,  for  the  "  later  sedimen- 
tary beds,  both  to  the  north  and  south,  were  found  not  to  have 
been  continuous  over  the  mountain  system,  but  to  have  been 
deposited  in  waters  whose  shores  were  limited  by  the  lower 


510  PHYSIOGRAPHIC  ESSAYS 

reaches  of  the  range"  (a,  166).  Therefore  the  discordant  streams 
must  be  antecedent. 

It  appears  to  me  that  the  possibility  of  error  in  this  argument 
lies  in  the  omission  of  all  consideration  of  the  migration  of  di- 
vides and  the  resulting  adjustment  of  stream  courses  to  deep 
internal  structure ;  but  at  the  time  of  the  exploration  of  the 
Colorado  river,  this  important  process  in  the  development  of 
rivers  was  not  understood.  It  now  seems  only  natural  that  the 
original,  consequent,  cataclinal  streams,  flowing  down  the  slopes 
of  the  range  from  crest  to  flanks,  should  have  permitted  the 
opening  of  subsequent  monoclinal  branches  on  the  soft  beds 
that  they  discovered  ;  and  that  the  shifting  of  divides  in  these 
monoclinal  valleys  should  have  led  to  the  capture  of  several 
cataclinal  streams  by  that  particular  one  -of  the  subsequent 
branches  that  grew  out  from  the  master  stream,  the  Green  river 
itself.  Thus  it  must  happen  that  the  streams  "  which  head  near 
the  summit  of  the  range  and  running  down  the  flank  turn  into 
the  Green  river  are,  in  their  upper  courses,  cataclinal,  and  when 
they  turn  to  follow  the  strike  of  the  rocks  into  Green  river,  are 
monoclinal"  («,  161),  this  being  a  normal  result  of  river  work 
in  cutting  down  the  thousands  of  feet  of  rocks  of  various  hard- 
nesses here  concerned.  The  smaller  streams  of  the  Uinta  range 
are  therefore  certainly  not  of  necessity  antecedent  to  the  Uinta 
uplift ;  the  probability  is  that  they  were  originally  purely  conse- 
quent, and  that  at  present  they  are  nicely  adjusted  to  the  struc- 
tures that  they  have  discovered. 

I  have  learned  so  much  from  the  doctrine  of  base-leveling,  as 
presented  in  Major  Powell's  writings,  that  I  shall  hope  to  profit 
by  the  lesson  of  the  Uinta  drainage  as  well ;  that  is,  the  possi- 
bility that  an  apparently  sound  conclusion  may  be  overturned 
when  new  processes  that  bear  upon  it  are  discovered.  It  is  here 
said  that  the  drainage  of  the  Watchung  crescent  in  New  Jersey 
is  an  example  of  partial  adjustment  following  a  superimposed 
origin  ;  hence  the  necessity  of  watching  closely  for  the  discovery 
of  new  principles  in  the  history  of  river  work  that  may  call  for 
a  revision  of  this  conclusion. 

Anaclinal  and  Reversed  Rivers  in  New  Jersey.  There  are  two 
other  examples  of  peculiar  accidents  in  the  history  of  rivers  in 


THE  RIVERS  OF  NORTHERN  NEW  JERSEY          5  1 1 

New  Jersey  to  which  I  wish  to  call  attention  ;  both  of  them  are  in 
the  latest  cycle  of  the  development  of  the  state,  that  is,  in  the 
cycle  which  has  changed  the  central  region  from  its  even  base- 
leveled  lowland  surface  to  the  pastplain  as  we  now  see  it.  Like 
the  uplift  of  the  Schooley  (highland)  peneplain,  the  uplift  of  the 
central  plain,  in  passing  from  the  second  to  the  third  cycle, 
was  not  uniform  throughout,  but  was  greater  in  one  place  than 
in  another.  In  the  neighborhood  of  the  lower  Raritan  river  a 
distinct  though  gentle  slope  to  the  northwest  is  apparent  in  the 
unconsumed  surface  of  the  pastplain ;  but  this  strong  river  runs 
southeastward  against  the  slope ;  it  is  an  anaclinal  stream.  The 
tilting  of  the  pastplain  is  moderate,  and  its  rocks  are  weak ;  the 
river  is  large  and  strong ;  its  anaclinal  course  is  therefore  best 
explained  by  regarding  it  as  a  mild  example  of  an  antecedent 
stream.  But  Ambrose's  brook,  a  small  stream  to  one  side  of 
the  Raritan,  flows  northwest  with  the  gentle  slope  that  was 
given  to  the  pastplain ;  it  is  therefore  not  a  survivor  from  the 
previous  cycle,  but  is  a  new  stream  consequent  on  the  slight 
deformation  by  which  the  latest  cycle  here  considered  was  ush- 
ered in.  Manalapan  and  Assanpink  are  apparently  of  the  same 
kind  (see  Fig.  37). 

The  Millstone  river  appears  to  be  intermediate  as  respects 
origin  between  the  Raritan  river  and  Ambrose's  brook.  It  appears 
still  to  lie  for  the  most  part  in  the  channel  that  it  occupied  be- 
fore the  elevation  and  tilting  of  the  base-leveled  central  plain, 
but  the  tilting  of  the  plain  seems  to  have  reversed  its  direction 
of  flow.  It  rises  near  the  center  of  the  state  and  flows  north- 
westward till  it  joins  the  Raritan  near  Somerville,  and  on  the 
way  it  crosses  from  the  thrown  or  depressed  to  the  heaved  or 
elevated  side  of  the  fall  line,  and  passes  through  a  deep  gap 
in  the  trap  ridge  of  Rocky  hill,  back  of  Princeton.  I  believe 
there  is  no  other  Atlantic  river  which  runs  against  the  fall  line 
in  this  way,  and  it  is  certainly  at  first  sight  remarkable  that  a 
stream  of  moderate  size  like  the  Millstone  should  have  held  its 
own  against  a  displacement  that  sufficed  to  deflect  great  rivers 
like  the  Delaware  and  the  Susquehanna  from  their  courses. 

The  Millstone  appears  to  have  been  a  stream  of  the  normal 
kind  in  the  previous  cycle  before  the  tilting  of  the  central  plain, 


512  PHYSIOGRAPHIC  ESSAYS 

when  it  probably  ran  southeastward  with  its  fellows  and  carried 
off  its  share  of  waste  in  the  base-leveling  process  of  that  time. 
No  other  supposition  than  this  seems  consistent  with  the  gen- 
eral history  of  the  region.  It  was  during  that  cycle  that  the 
deep  gap  was  cut  in  the  Rocky  hill  trap  ridge.  Then  came  the 
deformation  of  the  base-leveled  plain,  the  relatively  recent 
elevation  and  gentle  tilting  that  have  permitted  the  streams  to 
carve  it  into  a  pastplain,  and  with  this,  the  dislocation  along 
the  fall  line.  The  inclination  of  the  interstream  surfaces  of  the 
pastplain  leaves  no  doubt  that  it  was  tilted  to  the  northwest, 
and  to  this  tilting  we  must  ascribe  the  present  direction  of  the 
Millstone  flow.  But  why  did  not  the  accompanying  dislocation 
on  the  fall  line  throw  this  moderate-sized  stream  off  its  track 
and  divert  it  southwestward  to  the  Delaware  at  Trenton,  or 
northeastward  to  the  Raritan  below  New  Brunswick?  The  ef- 
fect of  the  dislocation  appears  with  considerable  distinctness 
along  a  line  from  Trenton  towards  Amboy,  in  the  less  altitude  of 
the  general  surface  of  the  pastplain  to  the  southeast  than  to  the 
northwest  of  the  line,  the  difference  of  altitude  of  the  two  parts 
being  about  a  hundred  feet.  The  persistence  of  the  Millstone 
against  such  a  dislocation  seems  to  require  that  we  should  pos- 
tulate a  slower  and  smaller  movement  here  than  that  which  de- 
flected the  Delaware. 

The  reversed  course  of  the  Millstone  cannot  be  regarded  as 
an  example  of  inversion  following  a  capture  of  its  ancient  north- 
ern headwaters  by  a  branch  of  the  Raritan ;  for  in  such  a  case 
surely  the  inversion  could  not  have  progressed  farther  south 
than  the  hard  trap  ridge  of  Rocky  hill,  where  a  stable  divide 
would  have  been  formed ;  nor  can  the  Millstone  be  regarded  as 
an  original  stream,  first  developed  and  consequent  upon  the  def- 
ormation of  the  central  plain,  for  in  that  case  it  should  consist 
of  two  separate  parts  :  one  part  running  from  the  actual  head 
of  the  river  to  the  fall  line,  where  it  would  turn  southwest  and 
cross  the  faint  flat  divide  that  separates  it  from  the  Delaware ; 
the  other  part  beginning  by  Princeton,  north  of  the  fall  line, 
and  running  thence  north  to  the  Raritan.  The  continuity  of 
these  two  parts  in  the  actual  Millstone  seems  to  be  explicable 
only  by  regarding  the  river  as  the  upper  portion  of  a  single 


THE  RIVERS  OF  NORTHERN  NEW  JERSEY          513 

larger  river  that  had  reached  an  old  age  in  the  previous  cycle ; 
it  was  then  broken  in  two  at  the  head  of  the  present  river  where 
the  greatest  elevation  of  the  central  plain  occurred,  and  thus  had 
its  former  headwaters  reversed  from  the  southeast  to  a  north- 
west direction  of  flow  across  and  against  the  fall-line  break  by 
the  tilting  of  the  plain.  Only  in  this  way  can  the  deep  gap  in 
Rocky  hill  be  explained.  The  river  is  thus  consequent  on  the 
tilting  of  the  plain,  and  yet  antecedent  to  the  accompanying 
faulting.  It  cannot  be  called  an  original  stream,  for  it  had  an 
ancestor  in  its  very  channel.  It  is  not  a  purely  consequent 
stream,  for  it  runs  against  the  heaved  side  of  a  fault.  It  is  not 
a  strictly  antecedent  stream,  for  it  flows  in  a  direction  deter- 
mined by  a  disturbance  that  occurred  late  in  its  life.  It  is  too 
exceptional  a  stream  to  have  a  generic  name.  We  cannot  expect 
to  find  many  others  like  it. 

The  result  that  has  been  of  the  greatest  interest  to  me  in 
these  studies  is  the  discovery  of  well-recorded  and  peculiar  his- 
tories in  the  commonplace,  small-sized  rivers  of  our  Atlantic 
slope.  We  have  looked  for  some  years  to  the  West  as  the  region 
where  river  history  should  be  illustrated,  because  it  was  there 
that  the  pioneers  in  this  branch  of  study  taught  us  the  lessons 
on  which  our  further  work  must  depend.  But  home  study  as 
well  as  distant  travel  has  its  rewards,  and  with  the  progress 
of  good  topographical  work  on  this  side  of  the  country  we  con- 
fidently await  much  instruction  from  a  close  acquaintance  with 
the  curious  histories  of  many  of  our  rivers  which  we  know  now 
only  by  name. 

REFERENCES 

Davis,  W.  M.    Am.  Jour.  Set.,  XXXVII  (1889),  430. 
Emmons,  S.  F.    Fortieth  Parallel  Survey,  II  (1877),  194,  205,  206. 
Powell,  J.  W.  (a)  Exploration  of  the  Colorado  River  of  the  West.      1875. 
(6)  Geology  of  the  Uinta  Mountains.      1876. 


XXI 

RIVER  TERRACES  IN   NEW  ENGLAND 

I.   GENERAL  STATEMENT 

Theories  of  River  Terraces.  The  terraces  carved  by  streams 
in  the  washed  drift  of  our  valleys  have  been  frequently  studied 
and  described  since  the  beginnings  of  geological  investigation 
in  New  England.  In  nearly  all  cases  more  attention  has  been 
given  to  terrace  pattern  as  seen  in  vertical  cross  section  than  as 


FIG.  44 

presented  in  horizontal  plan.  The  cross  section  is  usually  repre- 
sented as  in  Fig.  44,  in  which  the  depth  of  the  rock-floored  valley 
is  made  greater  than  that  of  the  new  valley  carved  in  the  drift 
filling.  A  notable  feature  of  such  terrace  sections  is  that  the 
open  space  measured  across  the  valley  between  the  scarps  of 
the  low-level  terraces  is  narrower  than  that  between  the  scarps 


FIG. 45 

of  the  high-level  terraces ;  and  this  fact  has  frequently  given 
rise  to  the  supposition  that  the  volume  of  our  streams  to-day  is 
less  than  that  of  the  streams  by  which  the  high-level  terraces 
were  carved.  It  will,  however,  be  shown  from  what  follows  that 
the  characteristic  cross  section  of  a  terraced  valley  in  which  the 


RIVER  TERRACES  IN  NEW  ENGLAND  515 

river  has  not  yet  reached  rock  bottom  exhibits  few  stepping 
terraces,  and  is  fairly  represented  by  Fig.  45  ;  while  if  stepping 
terraces  are  present,  a  characteristic  section  on  which  the  most 


FIG.  46 

significant  points  for  a  mile  or  more  up  and  down  the  valley  are 
projected,  would  show  that  the  base  of  many  of  the  terraces  is 
determined  for  short  distances  (ten  to  fifty  feet)  by 'a  rock  ledge, 
as  in  Fig.  46,  or,  better,  in  Fig.  47.  This  factor  in  the  develop- 
ment of  terraces  was  first  recognized,  as  far  as  my  reading  has 


FIG.  47 

gone,  by  Hugh  Miller  (the  younger),  whose  view  will  be  presented 
in  abstract  on  a  later  page. 

Although  the  controlling  ledges  occupy  a  very  small  fraction 
of  the  terrace  length,  they  are  of  dominant  importance,  and 
there  can  be  little  doubt  that  the  finest  flights  of  stepping 


FIG.  48 

terraces  in  New  England  are  to  be  thus  explained.  Terraces  of 
the  kind  shown  in  Fig.  48  are  different  from  those  here  studied, 
as  will  be  more  fully  stated  in  the  next  section. 


5i6  PHYSIOGRAPHIC  ESSAYS 

When  the  terrace  pattern  is  considered  in  plan  as  well  as  in 
cross  section,  it  appears  that  our  terraces  may  be  accounted  for, 
first,  by  the  behavior  of  a  meandering  and  swinging  stream, 
slowly  degrading  a  previously  aggraded  valley  without  change 
in  volume  ;  and  second,  by  the  control  exerted  here  and  there 
over  the  lateral  swinging  of  the  stream  through  the  discovery 
of  rock  ledges,  as  suggested  by  Miller.  The  following  pages 
are  devoted  to  a  fuller  consideration  of  this  conclusion. 


II.    PRELIMINARY  INQUIRY 

Variotis  Kinds  of  Terraces.  For  the  sake  of  clearness  it  is 
desirable  to  exclude  at  the  outset  all  kinds  of  terraces  other 
than  those  here  studied.  The  terraces  that  occupy  so  many  of 
our  valleys  are  known  as  river  terraces,  drift  terraces,  or  alluvial 
terraces.  They  have  as  to  origin  nothing  in  common  with  the 
terraces  of  sea-shores,  such  as  occur  on  the  coastal  slopes  of 
Cuba,  or  with  the  lake-shore  terraces  so  well  developed  in  the 
basins  of  Bonneville  and  Lahontan.  They  bear  little  resemblance 
to  structural  rock  benches,  such  as  break  the  slopes  of  valley 
sides  in  dissected  plateaus,  as  in  West  Virginia,  or  on  a  still 
larger-  scale  in  the  Colorado  canon.  They  have  little  likeness  to 
the  silt  and  gravel-covered  rock  terraces  formed  when  a  graded 
river,  revived  by  uplift,  cuts  a  new  valley  in  its  former  valley 
floor,  as  along  the  gorge  of  the  Rhine  on  its  way  through  the 
Schiefergebirge  of  western  Germany. 

Our  'New  England  drift  terraces  have  a  flat  and  nearly  level 
upper  surface  or  plain,  limited  backwards  by  rising  ground  and 
forwards  by  falling  ground,  and  to  that  extent  they  resemble  the 
terraces  of  all  the  classes  above  mentioned,  but  they  have  cer- 
tain well-marked  features  of  their  own.  They  are  evidently  the 
river-carved  remnants  of  a  body  of  stratified  clays,  sands,  or 
gravels  that  once  occupied  in  larger  volume  than  to-day  the 
rock-floored  valleys  of  still  earlier  origin.  Their  upper  surface, 
the  terrace  plain  or  floor,  slopes  with  the  fall  of  the  stream  by 
which  their  scarped  face  or  front  has  been  eroded ;  and  in  this  they 
differ  from  sea-shore  and  lake-shore  terraces  and  from  structural 
rock  benches,  none  of  which  have  any  particular  relation  to  the 


RIVER  TERRACES  IN  NEW  ENGLAND  517 

slope  of  neighboring  streams.  They  consist  of  unconsolidated, 
stratified  drift ;  if  a  ledge  appears  in  any  part  of  a  drift  terrace, 
it  is  manifestly  an  accidental  element,  although,  as  will  be  shown, 
it  may  exert  a  controlling  influence  on  the  pattern  of  the  terrace 
front ;  in  this  our  drift  terraces  differ  from  the  structural  rock 
benches  of  valley  sides  in  dissected  plateaus,  and  from  the  rock 
terraces  that  represent  the  former  valley  floors  of  revived  rivers, 
both  of  which  consist  essentially  of  rock,  even  though  the  latter 
may  bear  a  veneer  of  river  drift  on  their  surface,  as  in  Fig.  48. 
Moreover,  drift  terraces  are,  in  nearly  all  cases,  developed  with 
much  more  irregularity  of  pattern  than  is  the  case  with  the  ter- 
races of  other  kinds.  A  single  drift  terrace  —  unless  it  be  the 
highest  one  of  a  series  —  is  seldom  traceable  many  miles  along 
a  valley  side ;  its  length  may  be  only  a  few  hundred  yards. 
Terraces  of  other  kinds  are  usually  much  more  persistent. 

Furthermore,  our  drift  terraces  differ  from  other  terraces  in 
the  place  that  they  occupy  in  the  geographical  cycle.  They  are 
not  products  of  normal  erosion  during  an  undisturbed  stillstand 
of  a  land  mass,  but  are  the  consequence  of  some  relatively  short- 
lived episode  during  which  a  greater  or  less  departure  is  made 
from  the  normal  progress  of  a  cycle.  The  terraces  of  New  Eng- 
land occupy  well-opened  rock-floored  valleys  of  earlier  origin, 
and  thus  imply  the  previous  attainment  of  maturity  in  the  cycle 
which  witnessed  the  development  of  our  hills  and  valleys.  The 
glacial  period  witnessed  certain  modifications  of  the  pre-glacial 
valleys  and  closed  with  the  accumulation  of  abundant  drift  in 
them,  as  well  as  with  certain  changes  of  level  by  which  the 
rivers  were  prompted  to  wash  the  valley  drift  away.  Post-glacial 
time  has  allowed  the  rivers  to  enter  well  upon  this  task  ;  yet, 
even  when  the  task  has  been  completed,  the  normal  cycle  of 
erosion  in  New  England  will  not  have  advanced  far  beyond 
its  pre-glacial  phase,  —  so  brief  are  the  glacial  and  terrace  epi- 
sodes compared  to  the  time  required  for  base-leveling  a  region 
of  resistant  rocks. 

Systematically  considered,  river  terraces  may  be  best  associ- 
ated with  the  forms  assumed  by  the  waste  of  the  land  on  the 
way  to  the  sea.  Flood  plains  and  alluvial  fans  are  representative 
examples  of  the  form  assumed  by  land  waste  while  it  is  stopping 


518  MVSlOGRAPHIC  ESSAYS 

on  its  way  down  a  valley.  Terraces  are  examples  of  the  forms 
assumed  by  waste  that  still  remains  in  its  stopping  place  after 
part  of  its  volume  has  been  swept  forward  again. 

Terrace  Patterns,  Before  entering  upon  the  consideration  of 
the  process  of  terracing  it  will  be  well  to  examine  briefly  the 
more  characteristic  elements  of  terrace  pattern,  especially  as  seen 
in  horizontal  plan.  The  plain  or  floor  of  a  drift  terrace  frequently 
presents  a  rapid  variation  in  width,  usually  terminating  in  points 
at  its  upstream  and  downstream  ends,  as  in  Fig.  49.  The  bor- 
ders are  prevailingly  formed  of  curves  of  greater  or  less  length, 


FIG.  49 

but  of  tolerably  uniform  radius,  concave  to  the  stream  and  fre- 
quently uniting  in  cusps.  When  several  cusps  are  grouped,  one 
back  of  the  other,  so  as  to  form  a  strong  salient,  they  may  be 
called  a  terrace  spur.  Convex  borders  fronting  the  stream  occur 
but  rarely.  The  highest  plain  of  a  flight  of  terraces  backs  against 
the  ascending  slopes  of  the  older  valley  side  and  accepts  their 
outline  as  its  border,  as  in  Fig.  49  ;  while  each  lower  terrace,  as 
well  as  the  existing  flood  plain,  —  the  " intervale,"  or  "  interval  " 
of  New  Englanders, — backs  against  the  scarp  of  the  next  higher 
terrace;  thus  the  intermediate  members. of  a  flight  of  terrace 
steps  possess  similar  but  not  necessarily  parallel  outlines,  front 
and  back ;  the  cusps  between  the  curves  all  point  towards  the 
stream.  The  back  border  of  a  terrace  is  frequently  followed  by 


RIVER  TERRACES  IN  NEW  ENGLAND  519 

a  marshy  channel  from  which  the  terracing  stream  has  been 
withdrawn  by  a  short-cut,  or  cut-off  (as  is  more  fully  considered 
below),  before  the  channel  was  filled  ;  terrace  plains  thus  char- 
acterized may  slope  gently  away  from  the  axis  of  the  valley 
towards  their  back  border,  and  if  they  are  of  moderate  breadth, 
the  backward  slope  may  be  a  relatively  conspicuous  feature,  as 
in  the  lower  terrace  in  the  middle  of  Fig.  49.  Terraces  of  this 
kind  were  called  "  glacis  terraces  "  by  Hitchcock  (58).  They  are 
of  very  common  occurrence,  and  serve  to  show  that  the  sudden 
withdrawal  of  the  terracing  stream  from  a  roundabout  channel 
to  a  more  direct  course  has  not  been  unusual. 

The  scarp  of  a  terrace  connects  the  front  border  of  the  plain 
above  with  the  back  border  of  the  plain  below.  Its  sloping  sur- 
face therefore  presents  a  succession  of  curved  reentrants,  sepa- 
rated by  salients  of  greater  or  less  acuteness.  It  is  well  known 
that  the  curved  terrace  fronts  have  been  carved  by  the  suc- 
cessive encroachments  of  a  curved  stream  which  once  swung 
against  their  base,  and  that  the  stream  has  swung  laterally  at 
least  as  many  times  as  there  are  terraces  ;  but  the  behavior 
of  the  swinging  stream  has  seldom  been  traced  in  detail. 

Although  the  plain  and  the  descending  scarp  at  its  front  are 
usually  taken  together  as  bounding  a  terrace,  these  two  surfaces 
are  not  genetically  connected  in  river  terraces  as  they  are  in 
constructional  lake-shore  or  delta  terraces.  River  terraces  being 
of  destructional  origin,  it  is  the  ascending  scarp  at  the  back  of 
a  terrace  that  should  be  associated  with  the  plain  beneath  and 
in  front  of  it.  The  line  along  the  reentrant  edge  between  the 
plain  and  the  ascending  slope  at  its  back  is  the  most  significant 
of  all  terrace  lines.  The  front  line  of  a  terrace  plain  is  of  less 
significance,  for  it  is  determined  merely  by  the  slipping  of  the 
sands  and  clays  down  to  the  line  of  the  under-cut  scarp  at  the 
back  of  the  next  lower  terrace  ;  the  front  line  of  a  terrace  plain 
is  therefore  of  value  only  in  so  far  as  it  represents  the  back  line 
of  the  next  terrace  beneath. 

Terrace  scarps  are  steepest  where  the  cutting  stream  has 
most  recently  swung  against  their  base.  In  a  series  of  stepping 
terraces,  the  youngest  and  steepest  scarps  are  at  the  bottom  of 
the  flight ;  but  when  all  the  terraces  of  intermediate  levels  are 


520  PHYSIOGRAPHIC  ESSAYS 

destroyed  by  a  chance  lateral  swing  of  the  stream  so  that  it  under- 
cuts even  the  highest  terrace  plain,  then  the  whole  descent  from 
highest  to 'lowest  level  may  be  fresh-cut  with  sharp  edges  at  top 
and  bottom.  In  older  terraces  the  scarps  weather  to  a  gentler 
slope,  and  the  edges  are  rounded  off.  A  convex  slope  of  erosion 
is  thus  formed  above  and  a  concave  slope  of  deposition  below. 
The  older  the  terrace,  the  greater  is  the  part  of  its  front  occupied 
by  rounded  slopes,  and  the  gentler  is  the  slope  of  the  shortened 
tangent  between  them.  At  the  same  time,  the  salients  or  cusps 
between  the  reentrants  of  the  scarps,  as  seen  in  plan,  lose  their 
original  sharpness  of  definition  and  become  blunt  and  dulled. 
There  has  been  no  attempt  to  show  details  of  this  kind  in  the 
accompanying  diagrams. 

Gulches  are  often  worn  in  terrace  fronts  by  wet-weather 
streams,  and  fans  are  spread  on  the  terrace  plain  below.  The 
abandoned  stream  channels  at  the  back  border  of  a  plain  are 
usually  taken  as  guides  for  surface  drainage,  whose  gathered 
waters  dissect  the  plain  where  it  is  cut  off  by  the  next  lower 
terrace.  A  rather  systematic  drainage  pattern  is  thus  devel- 
oped, as  in  Fig.  49. 

The  several  theories  by  which  terraces  have  been  explained 
may  now  be  reviewed. 

Terraces  carved  by  Streams  of  Diminishing  Volume.  The  primi- 
tive explanation  of  terraces  is  that  the  whole  space  between  the 
upper  terrace  scarps  represents  the  channel  of  a  huge  river  by 
which  the  valley  was  once  drained,  and  that  successive  diminu- 
tions of  volume  to  that  of  the  present  river  are  indicated  by  the 
decrease  of  breadth  between  the  terraces  in  descending  order. 
Although  this  view  has  sometimes  received  distinguished  advo- 
cacy, it  has  never  gained  general  acceptance  among  geologists  or 
geographers.  It  has,  however,  been  very  generally  supposed  that 
the  present  rivers  are  much  smaller  than  they  were  when  they 
began  the  work  of  terracing ;  hence  it  is  desirable  to  consider 
the  special  features  that  should  appear  if  a  decrease  in  stream 
volume  had  actually  taken  place. 

The  best  indication  of  the  volume  of  the  stream  by  which  a 
terrace  has  been  carved  is  afforded  by  the  curvature  of  its  frontal 
scarp.  If  the  scarps  of  the  low-level  terraces  have  a  radius  and 


RIVER  TERRACES  IN  NEW  ENGLAND  521 

an  arc  of  curvature  similar  to  these  elements  in  the  existing  river 
meanders,  and  significantly  smaller  than  in  the  high-level  scarps, 
while  curves  at  intermediate  levels  show  intermediate  values,  a 
diminution  of  stream  volume  may  be  fairly  inferred.  If  the  radius 
and  arc  of  curvature  are  of  about  the  same  measure  in  the  three 
cases,  no  change  in  stream  volume  is  indicated. 

On  the  other  hand,  if  a  stream  were  charged  with  abundant 
and  coarse  load  in  the  last  stages  of  its  aggrading  action,  as  seems 
to  have  been  frequently  the  case  in  New  England,  its  slope  must 
have  been  relatively  strong  ;  and  a  graded  river  with  a  heavy  load 
on  a  strong  slope  does  not  develop  curves  of  as  small  radius  as 
it  would  when  subsequently  flowing  with  the  same  volume  but 
with  a  finer  load  on  a  gentler  slope  ;  hence  a  large  radius  of  cur- 
vature in  the  uppermost  terraces  should  not  alone  be  taken  as 
an  indication  of  large  volume  ;  large  arc  of  curvature  should  also 
be  found  before  large  volume  is  inferred.  It  is  for  this  reason 
that  some  of  the  uppermost  terraces  of  the  Connecticut  and  the 
Westfield  rivers,  whose  scarps  se6m  to  sweep  in  curves  of  greater 
radius  than  do  those  of  the  low-level  terraces,  cannot  alone  give 
assurance  of  a  former  greater  volume  for  their  rivers. 

It  is,  however,  rendered  very  probable  by  what  is  known  of 
the  later  stages  of  the  glacial  period  that  many  of  our  streams 
had  greater  volume  then  than  now.  The  most  effective  cause 
for  greater  volume  was  the  constraint  of  the  ice  sheet,  whereby 
the  drainage  from  the  basins  of  north-flowing  rivers  was  turned 
over  the  divides  into  the  valleys  of  south-flowing  rivers.  This 
may  have  been  the  case  while  the  ice  still  covered  the  northern 
basins,  their  waters  (as  far  as  they  had  any)  then  running  as  sub- 
glacial  streams,  which  may  have  been  forced  to  ascend  slopes 
and  cross  divides.  Effective  constraint  may  also  have  been  pro- 
vided after  the  ice  had  at  least  in  part  withdrawn  from  the  north- 
ern basins  but  when  it  remained  in  sufficient  force  to  obstruct 
their  normal  outlets,  thus  forming .  lakes  whose  overflow  ran 
across  a  pass  in  the  divide  to  some  southern  valley.  Another 
cause  for  increased  volume  of  our  south-flowing  rivers  was  the 
importation  into  their  basins  of  a  considerable  snowfall  that  was 
received  on  the  ice  sheet  over  some  northern  basin.  A  fourth 
cause  for  increased  volume  of  our  rivers  lies  in  a  possibly  greater 


522  PHYSIOGRAPHIC  ESSAYS 

precipitation  during  the  later  stages  of  the  glacial  period  than 
at  present.  A  fifth  cause  lies  in  a  relatively  rapid  melting  of  the 
retreating  ice  sheet.  It  is  eminently  possible  that  these  various 
causes  may  have  contributed  effectively  to  an  increase  in  river 
volume  while  the  New  England  valleys  were  aggrading  with 
drift ;  but  it  does  not  follow  that  volumes  decidedly  larger  than 
those  of  to-day  were  continued  into  the  period  of  terracing. 

Except  where  direct  evidence  is  given  by  curvature  and  arc 
of  high-level  terrace  scarps,  a  formerly  greater  volume  of  the 
terracing  streams  should  be  regarded  only  as  a  possible,  not  as 
an  actual,  occurrence.  It  is  especially  desirable  that  large  bulk 
and  coarse  texture  of  terrace  deposits  should  not  be  too  readily 
accepted  as  evidence  of  former  greater  volume  of  streams ;  for 
bulk  of  deposits  is  a  function  of  time  as  well  as  of  rate  of  action, 
and  texture  is  a  function  of  slope  as  well  as  of  stream  volume  and 
velocity.  Hence  until  time  and  slope  are  shown  to  have  been 
insufficient  to  account  for  bulk  and  texture  of  deposits,  it  is  not 
compulsory  to  account  for  them  by  greater  stream  volume. 

Even  if  decrease  of  volume  has  been  of  general  occurrence 
during  the  period  of  terracing,  it  has  nevertheless  not  been  in 
control  of  terrace  development ;  for  if  it  had  been,  stepping  ter- 
races should  be  much  more  abundant  than  they  are  to-day.  As 
a  matter  of  fact,  the  diagrams  by  which  terraced  valleys  are  or- 
dinarily represented,  give  an  exaggerated  idea  of  the  prevalence 
and  perfection  of  these  graceful  forms.  It  is  rare  to  find  a  long 
flight  of  stepping  terraces  on  both  sides  of  a  valley;  it  is  rare  to 
find  a  flight  of  terraces  continued  for  any  long  distance  along 
a  valley  side ;  when  more  than  three  or  four  low  steps  are  to  be 
counted,  it  is  usually  only  for  a  moderate  fraction  of  a  mile  that 
they  persist.  A  large  part  of  the  length  of  our  terraced  valleys 
is  bordered  by  a  few  terraces  of  strong  scarps,  or  by  a  high  ter- 
race with  one  or  two  lower  ones  beneath  it ;  and  it  is  not  uncom- 
mon to  find  at  least  one  side  of  a  valley  inclosed  by  a  single  scarp 
in  which  the  whole  descent  is  made  at  once  from  the  highest  ter- 
race plain  to  the  lowest.  If  terracing  had  been  due  to  a  general 
decrease  in  the  volume  of  our  rivers,  stepping  terraces  should  be 
much  more  prevalent,  and  broad  flood  plains  between  the  high 
scarps  of  a  single  terrace  on  each  side  of  the  valley  should  be 


RIVER  TERRACES  IN  NEW  ENGLAND  523 

much  more  rare  than  they  are  ;  and  when  the  whole  descent  from 
high  terrace  to  flood  plain  is  made  in  a  single  scarp  on  one  side 
of  the  valley,  stepping  terraces  with  broad  treads  should  be  well 
developed  on  the  opposite  side  ;  but  no  such  arrangement  of  ter- 
race form  can  be  said  to  prevail.  Decrease  of  river  volume  must 
therefore  be  at  most  a  subordinate  cause  of  terracing,  if,  indeed, 
it  is  not  as  a  rule  a  negligible  factor  in  their  production. 

This  conclusion  seems  to  have  been  clearly  in  the  mind  of 
Adams,  state  geologist  of  Vermont,  who,  in  1846, wrote  as  follows: 

The  first  stage  in  the  process  in  which  the  terraces  originated,  the  dep- 
osition of  the  materials,  we  have  before  referred  to  the  older  Pleistocene. 
The  process  of  denudation  must  have  next  followed,  when  the  rivers,  cut- 
ting down  their  channels  through  the  drift  barriers,  lowered  them  gradually 
above  the  barriers.  Flowing  through  the  level  deposits  of  sand,  they  must 
have  formed  serpentine  channels,  as  rivers  do  now  in  alluvial  plains  ;  con- 
sequently, by  increasing  the  convexity  of  the  bends,  and  then  cutting  them 
off,  or  wearing  away  their  headlands  and  shifting  their  beds,  they  would  be 
meanwhile  removing  the  greater  part  of  the  materials  thus  disturbed.  By 
this  process  the  greater  portion  of  the  original  plain  must  have  been  carried 
off,  and  it  is  not  necessary  to  suppose  that  the  distance  between  opposite 
terraces  is  any  indication  of  greater  magnitude  of  the  river,  but  only  of  its 
shifting  its  channel  (145,  146). 

Terraces  carved  by  Streams  of  Increasing  Slope.  When  the 
basin  of  an  aggrading  river  system  is  slightly  tilted,  it  may  be 
expected  that  those  streams  whose  slopes  are  decreasing  will 
aggrade  their  valleys  more  rapidly  than  before,  unless  their  point 
of  junction  with  a  degrading  stream  may  be  lowered  more  than 
their  headwaters  are  depressed  by  tilting ;  while  those  whose 
slopes  are  increasing  will  change  their  action  from  aggrading  to 
degrading.  It  is  well  known  that  New  England  has  suffered  a 
differential  elevation  in  post-glacial  time.  The  post-glacial  clays 
of  Lake  Champlain  and  southern  Maine  were  deposited  when 
the  sea  stood  three  hundred  feet  or  more  above  its  present  level. 
The  clays  of  the  Connecticut  valley  in  Massachusetts  were,  ac- 
cording to  Emerson,  deposited  in  lakes  or  bodies  of  slack  water 
at  or  very  close  to  the  sea-level  of  their  time,  but  the  clays  now 
reach  elevations  approaching  two  hundred  feet.  No  post-glacial 
changes  of  level  of  such  amounts  are  known  to  have  taken  place 
along  the  southern  New  England  coast.  Our  south-flowing  rivers 


524  PHYSIOGRAPHIC  ESSAYS 

have  therefore  been  accelerated,  while  those  flowing  northward 
have  been  retarded  ;  and  to  this  differential  tilting  Shaler  has 
ascribed  the  weak  terracing  by  streams  of  the  latter  class  in 
contrast  to  the  active  terracing  by  those  of  the  former. 

While  it  is  thus  made  very  probable  that  the  erosion  of  valley 
drift  was  determined  by  the  unequal  elevation  of  New  England 
in  post-glacial  time,  it  does  not  follow  that  individual  terraces 
are  in  any  close  way  related  to  this  movement.  Several  cases 
must  be  here  distinguished. 

The  northern  uplift  may  have  been  accomplished  in  a  single 
movement  and  so  rapidly  as  to  have  revived  the  streams  to  an 
unusual  activity  of  erosion,  whereby  they  deepened  their  valleys 
quickly  for  a  time,  and  did  not  begin  to  swing  laterally,  in  the 
manner  essential  to  terracing,  until  they  had  developed  new 
grades  of  gentle  declivity  after  the  rapid  uplift  had  ceased.  In 
this  case  only  a  single  high-level  terrace  and  no  intermediate 
terraces  would  be  formed,  and  there  would  be  but  few  low-level 
terraces. 

A  second  supposition  includes  cases  of  repeated  rapid  uplifts 
separated  by  deliberate  pauses,  each  of  which  would  produce  a 
result  similar  to  that  of  the  previous  case.  Here  we  should  ex- 
pect the  river  to  have  swung  laterally  at  as  many  different  levels 
as  there  had  been  pauses  during  the  total  uplift ;  and  the  flood 
plain  formed  during  each  pause  would  be  of  relatively  persistent 
occurrence  down  the  valley.  But  in  order  to  protect  the  terrace 
remnants  of  the  successive  flood  plains  from  being  consumed  by 
the  river  when  it  swings  from  side  to  side  at  lower  levels,  it  is 
necessary  to  postulate  that  the  movements  of  uplift  should  suc- 
ceed each  other  at  shorter  and  shorter  intervals,  so  that  the  later- 
carved  flood  plains  should  be  narrower  than  the  earlier  ones.  The 
chief  objection  to  this  supposition  is  not  so  well  directed  against 
the  postulate  just  mentioned  as  against  the  requirement  of  cor- 
related levels  in  the  terrace  on  the  two  sides  of  a  valley.  Such 
correlation  is  occasionally  found,  but  it  is  by  no  means  character- 
istic of  our  terraced  valleys  in  general.  The  terrace  levels  are 
usually  so  discordant  on  the  opposite  sides  of  a  valley  that  they 
cannot  be  considered  the  records  of  stillstands  of  the  land  be- 
tween times  of  rapid  uplift. 


RIVER  TERRACES  IN  NEW  ENGLAND  525 

A  third  supposition  considers  an  uplift  so  slow  that  the  south- 
flowing  rivers  were  never  much  accelerated  ;  for  during  slow  up- 
lift the  larger  rivers  might  continue  to  swing  actively  from  side 
to  side,  while  all  the  time  degrading  the  valley  floor.  In  this 
case  terraces  might  be  cut  at  many  different  levels  on  opposite 
sides  of  the  valley,  according  to  the  habit  of  the  river  in  its 
lateral  swinging. 

The  third  supposition  seems  most  appropriate  to  New  Eng- 
land, for  all  of  our  valleys  in  which  terraces  are  well  developed, 
exhibit  flood-plain  remnants  at  many  levels,  high  and  low,  and 
neither  so  few  in  number  nor  so  accordant  in  relative  altitude 
above  the  river  as  to  imply  that  lateral  swinging  had  occurred 
only  during  the  quiet  intervals  between  rapid  uplifts.  But  it 
should  be  noted  that  this  conclusion  applies  better  to  the  valleys 
of  good-sized  streams  or  rivers  than  to  those  of  small  brooks  ;  for 
the  latter  frequently  show  only  faint  terraces  or  no  terraces  at  all, 
even  though  they  are  branches  of  rivers  whose  valleys  are  well 
terraced.  This  seems  to  mean  that  an  uplift  which  was  so  slow 
that  a  good-sized  river  could  easily  keep  pace  with  it  by  down- 
cutting,  may  have  been  too  fast  for  such  a  result  in  the  case  of 
a  small  stream.  While  the  able-bodied  rivers  may  thus  have  been 
always  effectively  at  grade,  leisurely  swinging  from  side  to  side 
and  at  the  same  time  slowly  wearing  down  their  valley  floors, 
the  small  streams  may  have  been  for  much  or  all  of  this  time 
above  grade,  and  therefore  unable  to  widen  their  little  valleys, 
although  actively  engaged  in  deepening  them.  On  the  other 
hand,  even  the  largest  rivers  have  not  been  able  to  maintain 
a  graded  channel  in  the  rock  ledges  upon  which  they  have 
been  here  and  there  superposed  by  the  drift  cover.  They  are 
still  actively  cutting  down  such  ledges,  but  they  are  not  yet  able 
to  widen  the  rock  notch  that  they  are  cutting,  thus  imitating  the 
condition  of  their  smallest  branches,  which  have  not  yet  been 
able  to  widen  their  little  valleys  even  in  clays  and  sands.  Bowlder 
clay  or  till  is  of  a  resistance  between  the  feebleness  of  stratified 
drift  and  the  strength  of  rock  ledges.  If  a  mass  of  till  is  dis- 
covered, the  stream  may  be  successful  in  cutting  down  its  chan- 
nel to  grade,  and  yet  unsuccessful  in  opening  a  valley  floor  ;  and 
thus  a  bowlder-clay  "  shut  in  "  may  be  produced  between  open 


526  PHYSIOGRAPHIC  ESSAYS 

valley  floors  or  "  intervals  "  that  have  been  eroded  in  weak  strati- 
fied drift  farther  up  and  down  stream.  Little  river,  a  mile  south- 
west of  Westfield,  Massachusetts,  offers  examples  of  this  kind. 

The  small  changes  made  in  rock  ledges  during  the  develop- 
ment of  an  extended  series  of  river  terraces  serve  to  indicate 
how  short  is  the  duration  of  the  episode  in  which  the  alluvial 
filling  of  a  valley  is  terraced,  in  comparison  with  the  time  needed 
for  the  erosion  of  the  rock-bound  valley  itself,  or  still  more  with 
a  whole  cycle  of  erosion,  in  which  a  mountain  mass  is  reduced 
to  a  plain  of  degradation. 

While  slow  uplift  is  thus  seen  to  be  consistent  with  the  pro- 
duction of  many  terraces,  it  is  not  consistent  with  their  preser- 
vation, for  it  does  not  explain  the  diminution  of  the  interscarp 
space  from  the  higher  to  the  lower  levels.  Indeed,  the  present 
rivers  might  tend  to  develop  broader  flood  plains  by  strong  lateral 
swinging  at  the  faint  grades  now  assumed  than  they  had  devel- 
oped at  the  stronger  grades  during  the  earlier  stages  of  possibly 
more  active  uplift  and  heavier  load ;  and  the  broad,  low  flood 
plains  would  necessitate  the  under-cutting  of  all  or  nearly  all  the 
earlier  high-level  terraces  by  the  present  stream,  and  the  concen- 
tration of  nearly  all  the  separate  scarps  in  a  single  high-terrace 
front,  as  in  Fig.  45.  Examples  in  which  this  condition  has  been 
actually  attained  are  to  be  found  in  the  valleys  of  various  rivers, 
as  will  be  more  fully  set  forth  in  following  pages.  Single  high- 
scarped  terraces  are  indeed  so  common  as  to  warrant  the  con- 
clusion that  high-level  and  intermediate  terraces  would  nearly 
always  be  destroyed  by  the  swinging  of  the  river  at  a  lower 
level  but  for  the  occurrence  of  some  special  conditions  by 
which  they  are  preserved. 

Terraces  carved  by  Streams  of  Diminishing  Load.  A  graded 
river  may  be  caused  to  degrade  as  well  by  diminishing  its  load 
as  by  increasing  its  slope,  volume  remaining  constant.  A  dimi- 
nution of  load  since  the  stage  of  glacial  retreat  is  highly  probable, 
for  not  only  the  streams  that  issued  from  the  ice  sheet  but  those 
also  which  washed  the  freshly  exposed  drift-covered  land  surface 
were  in  all  probability  highly  charged  with  detritus  in  late  glacial 
and  early  post-glacial  time.  Indeed,  increase  of  load  may  have 
been  almost  as  potent  a  cause  of  filling  the  valleys  with  washed 


RIVER  TERRACES  IN  NEW  ENGLAND          527 

drift  as  was  the  depressed  attitude  of  the  land  in  the  north  and 
the  consequent  enfeebled  slope  of  the  south-flowing  rivers.  As 
the  ice  disappeared  and  as  the  land  surface  was  more  or  less 
covered  with  vegetation,  the  load  of  the  streams  should  have 
been  lessened,  and  they  must  thereupon  have  set  to  work  to  de- 
grade the  valleys  that  they  had  just  before  been  aggrading,  even 
if  no  change  of  slope  had  taken  place.  This  process,  if  working 
alone,  must  have  been  very  gradual,  and  might  therefore  have 
allowed  plenty  of  time  for  lateral  swinging  and  terrace  carving. 
But,  as  before,  no  explanation  is  here  found  for  the  production 
of  stepping  terraces.  On  the  contrary,  when  the  diminution  of 
load  was  further  advanced,  the  rivers  would  degrade  their  valley 
floors  more  and  more  slowly,  and  the  tendency  would  then  be  to 
destroy  all  the  earlier  terraces  by  broadening  the  flood  plain  to 
a  maximum. 

That  the  rate  of  degradation  by  our  rivers  was  really  slow  is 
proved  by  the  flights  of  stepping  terraces  here  and  there  in  dif- 
ferent valleys  ;  and  that  the  normal  tendency  of  the  larger  rivers 
is  to  destroy  nearly  all  the  earlier-made  terraces  by  opening 
broad  flood  plains  at  low  levels  is  proved  by  the  frequent  occur- 
rence of  high  scarps  descending  from  the  highest  terrace  plain 
nearly  or  quite  to  the  lowest.  Hence  it  is  for  the  preservation 
of  high-level  and  intermediate  terraces  rather  than  for  their 
production  that  a  more  efficient  cause  than  any  yet  discussed 
is  to  be  sought. 

Preservation  of  Terraces  by  Rock  Ledges.  What  is  more  natu- 
ral than  that  a  river,  swinging  from  side  to  side  as  it  slowly 
degrades  its  valley  floor,  shall  here  and  there  be  restrained  on 
coming  against  a  ledge  projecting  from  the  sloping  valley  wall ; 
and  that  the  deeper  the  valley  is  excavated,  the  less  breadth  of 
free  swinging  can  remain !  This  idea  was  first  given  explicit 
statement  in  Miller's  paper  on  "  River  Terracing;  its  Methods 
and  their  Results,"  as  illustrated  by  observations  in  Scotland. 
After  a  review  of  earlier  writings,  this  author  says  : 

The  modern  rivers  .  .  .  have  struck  rock  at  very  variable  depths.  In 
hundreds  of  cases,  after  winding  freely  about,  encountering  only  soft  clays 
and  the  like,  and  constructing  terraces  of  various  kinds,  they  have  here 
and  there  become  rock-bound,  and  prevented  from  pursuing  their  work  of 


528  tHYSlOGRAPHiC  ESSAYS 

terrace-building  after  their  former  manner,  as  well  as  from  destroying  the 
terraces  they  had  already  made  (298).  .  .  . 

When  .  .  .  the  rivers  commenced  to  work  upon  shallow,  wide-bottomed 
valleys,  soft  and  yielding  in  their  nature,  except  where  crossed  by  bars  of 
rock  .  .  .,  they  proceeded  to  plane  far  and  wide,  traveling  from  breadth  to 
breadth  to  an  extent  never  now  equaled.  With  banks  nowadays  eight  or  ten 
times  as  high,  and  rock-bound  at  perhaps  ten  times  as  many  points,  it  is  no 
wonder  that  the  modern  rivers  should  seem  to  have  "  run  in  "  (299,  300). 

Rock  ledges,  however,  are  not  here  given  the  importance  they 
deserve.  The  reader  will  not  surely  gain  from  Miller's  article  a 
full  measure  of  the  value  of  ledges  in  determining  the  pattern 
of  terraces,  and  of  stepping  terraces  in  particular.  Hence  a  more 
detailed  statement  of  the  relation  of  ledges  to  terrace  pattern 
and  to  terrace  development  seems  desirable,  especially  with  ref- 
erence to  the  valleys  of  New  England,  where  this  explanation  of 
terraces  has  not  previously  been  applied. 

It  should  be  further  noted  that  certain  postulates  of  Miller's 
essay  do  not  command  entire  assent.  He  states  that  "  it  is  not 
allowable  to  have  recourse  to  coast  elevation,  or  climatic  changes, 
or  periodicity  of  any  kind,  without  first  proving  that  the  terraces 
range  in  opposite  pairs"  (304,  305).  This  seems  to  be  an  unnec- 
essary limitation  of  possibilities ;  for,  as  is  here  explained  on 
page  540,  a  river  that  is  impelled  to  gradual  degradation  by  a 
slow  rising  or  tilting  of  the  land  may  produce  unpaired  terraces 
as  it  wanders  to  and  fro  across  its  valley  floor.  On  another  page 
Miller  concludes  that  rivers  "cannot  but  concentrate  their  chan- 
nels as  they  excavate  them,  unless  the  amount  of  planation  is 
out  of  all  proportion  to  the  rate  of  deepening  "  (300),  and  seems 
to  imply  in  this  statement  that  a  large  ratio  of  lateral  erosion  to 
degradation,  such  as  is  here  assumed  for  our  New  England  riv- 
ers, and  further  considered  in  later  sections,  is  an  improbable 
ratio.  To  this  it  may  be  answered  that  the  occurrence  of  step- 
ping terraces  at  one  and  another  point  in  our  larger  valleys  cer- 
tainly justifies  the  assumed  ratio  by  showing  that  lateral  swinging 
should  be  measured  in  hundreds  or  thousands  of  feet  at  many 
successive  stages  of  degradation,  while  the  total  degradation  is 
usually  to  be  measured  in  tens  of  feet  and  seldom  exceeds  one 
or  two  hundred  feet.  A  possible  reason  for  the  difference  of 
values  given  to  this  ratio  may  be  that  Miller's  studies  were 


RIVER  TERRACES  IN  NEW  ENGLAND  529 

directed  to  the  moderate-sized  rivers  of  Scotland,  while  the  best 
terraced  valleys  in  New  England  are  those  of  large  rivers  like 
the  Connecticut  and  the  Merrimac  and  their  stronger  branches ; 
and,  as  has  been  already  pointed  out,  a  large  river  may  swing 
actively  during  an  uplift  that  gives  a  small  river  no  time  for 
anything  but  down-cutting.  These  two  items  are,  however,  of 
secondary  importance  in  Miller's  theory  compared  to  rock  ledges. 
In  reviewing  various  other  essays  of  earlier  dates  several  sug- 
gestive passages  have  been  found,  hinting  at  the  importance  of 
rock  ledges.  Adams  makes  the  following  statement : 

If  a  terrace  has  been  formed  before  the  complete  removal  of  the  obstruc- 
tions in  the  channel  [the  context  shows  that  these  obstructions  are  "  solid 
rock  "],  the  same  process  must  have  been  repeated  within  the  new  and  nar- 
rower level  of  interval.  We  should  thus  have  a  second  terrace.  Repetitions 
of  the  process  in  cases  where  the  obstructions  were  not  entirely  removed 
would  occasion  a  greater  number  of  terraces  (146). 

Something  more  explicit  is  found  in  Edward  Hitchcock's  "  Sur- 
face Geology."  In  describing  a  middle  section  of  the  Connecticut 
valley,  where  the  terraces  became  famous  from  the  writings  of 
this  author,  it  is  said  that  "  the  rock  often  projects  through  the 
terraces"  (18),  but  the  service  of  the  rock  in  protecting  the  over- 
lying terrace  from  being  cut  back  is  not  announced.  Further  on 
a  description  is  given  of  the  basin  of  the  Westfield  river,  where 
the  effect  of  ledges  in  determining  the  number  and  pattern  of 
the  terraces  is  very  striking ;  here  it  is  briefly  stated  that  "  the 
materials  of  which  all  these  terraces  are  formed  are  clay,  sand, 
and  gravel,  though  the  red  sandstone  shows  itself  occasionally 
near  the  river  "  (20).  The  secret  is  told  in  an  account  of  the  ter- 
races of  the  Deerfield  :  "  The  river  would  encroach  still  farther 
upon  this  hill,  had  it  not  struck  a  ledge  of  red  sandstone,  which 
will  at  least  retard  its  lateral  erosion"  (19);  and  again, 

the  reason  why  those  [terraces]  on  Pine  hill  remain,  I  find  to  be  that  they 
rest  on  a  protuberant  mass  of  red  sandstone.  On  the  west  side  of  the  hill 
...  is  an  ancient  bed  of  Deerfield  river  .  .  .  which  was  prevented  from 
making  any  further  lateral  encroachments  by  the  underlying  rock  (20). 

Yet  in  spite  of  the  understanding  thus  shown  of  the  importance 
of  ledges  in  these  particular  instances,  the  generality  of  the  rela- 
tion of  ledges  and  terraces  is  not  brought  forward  ;  and  the  above 


530  PHYSIOGRAPHIC  ESSAYS 

instances  of  the  local  restraint  exercised  by  ledges  have  never 
been  quoted,  so  far  as  I  can  find,  by  any  of  the  many  readers  of 
Hitchcock's  well-known  essay. 

A  fuller  recognition  of  the  part  played  by  defending  ledges  is 
to  be  found  in  Emerson's  "  Geology  of  Old  Hampshire  County, 
Massachusetts."  It  is  here  said  that  the  Connecticut  river  in 
the  neighborhood  of  Holyoke  "  has  now  cut  its  bed  deep  in  the 
sandstones  and  is  thus  prevented  from  oscillating "  (730).  A 
little  farther  down  the  valley  "  the  river  early  became  entangled 
in  rock  and  has  cut  only  vertically"  (733).  In  the  northern  part 
of  the  state  "  the  river  everywhere  cut  down  rapidly  to  rock  and 
has  not  swung  widely  to  east  and  west,  but  has  been  condemned 
from  the  beginning  to  rock-cutting  "  (733).  "Across  Chicopee 
there  is  a  fine,  low  terrace  bounded  on  the  east  by  a  high  scarp 
of  the  high  terrace,  which  everywhere  shows  till  in  great  force 
beneath  the*  sands  of  the  old  lake  "  (730  ;  see  also  627,  632).  It 
should  be  noted,  however,  that  these  passages  are  chiefly  con- 
cerned with  the  occurrence  of  trenches,  floored  with  rock  and 
lined  on  both  banks  with  ledges.  The  part  played  by  an  isolated 
ledge  of  rock  or  by  a  bank  of  till  in  preventing  the  further  swing- 
ing of  the  river  and  thus  defending  the  terraces  above  it  is  not 
brought  forward. 

Origin  of  Terraces  in  New  England.  Three  conclusions  may 
now  be  stated  in  order  that  the  reader  may  have  in  mind  the 
end  to  which  the  preceding  and  following  pages  lead.  First,  a 
diminution  of  stream  volume  may  have  taken  place  during  the 
terracing  of  our  New  England  valleys,  but  it  has  not  been  essen- 
tial to  the  production  of  the  observed  terraces.  Second,  the  ter- 
racing rivers  have  slowly  degraded  their  aggraded  valleys  while 
actively  swinging  from  side  to  side,  degradation  probably  being 
the  result  of  the  combined  action  of  a  slow  northern  uplift  and 
a  gradual  decrease  of  load,  and  in  spite  of  a  probable  decrease 
of  volume.  Third,  the  chance  discovery  of  rock  ledges  by  the 
swinging  river  is  the  chief  cause  of  the  systematic  diminution  of 
interscarp  space  and  of  the  preservation  of  terraces,  as  seen  in  a 
typical  section  of  stepping  terraces. 

A  full  statement  of  the  process  of  terracing,  therefore,  involves 
a  consideration,  first,  of  the  behavior  of  a  free-swinging,  slowly 


RIVER  TERRACES  IN  NEW  ENGLAND  531 

degrading  river;  and,  second,  of  the  constraint  that  may  be  im- 
posed on  such  a  river  by  the  accidental  encounter  with  previously 
buried  ledges  at  various  points  in  its  course  and  at  various  stages 
in  its  history.  This  anticipatory  statement  may  aid  in  the  under- 
standing of  the  following  pages. 


III.   THE  THEORY  OF  RIVER  TERRACES 

Plan  of  Statement.  The  previous  paragraphs  have  given  a 
general  consideration  of  several  theories  of  river  terraces,  with 
the  result  of  deciding  that  one  of  them  offers  a  much  better  ex- 
planation of  observed  facts  than  the  others.  It  is  now  proposed 
to  examine  the  successful  theory  with  more  care,  first,  by  making 
a  somewhat  detailed  study  of  such  processes  of  river  action  as 
are  involved  in  the  theory ;  second,  by  deducing  with  some  mi- 
nuteness the  various  patterns  of  terraces  that  can  be  formed  by 
these  river  processes.  It  will  then  be  possible  to  make  in  Part  IV 
a  thorough  test  of  the  verity  of  the  theory  by  confronting  its  de- 
duced consequences  with  the  facts  determined  by  observation. 

It  should  be  understood  that  the  deductive  character  of  the 
succeeding  paragraphs  is  more  apparent  than  real.  Many  fea- 
tures of  river  work  here  presented  as  deductions  were  discovered 
by  observation.  It  is  true  that  an  expectation  of  certain  occur- 
rences had  been  aroused  by  the  deductive  consideration  of  cer- 
tain processes,  but  there  has  been  so  continual  an  interweaving 
of  observation  and  theory  during  the  growth  of  these  pages  that 
it  is  now  rather  difficult  to  determine  the  order  in  which  the 
various  items  here  recorded  came  to  mind.  It  is  therefore  chiefly 
for  the  sake  of  a  continuous  presentation  of  the  theory  of  river 
terraces  that  a  largely  deductive  treatment  is  here  adopted.  When 
the  whole  theory  has  been  apprehended,  it  is  relatively  easy  to 
test  its  verity  by  observations  pertinent  to  its  different  parts. 

The  other  theories  of  terracing,  regarded  as  unsuccessful  in 
our  preliminary  inquiry,  should  be  further  considered  before  they 
are  discarded ;  but  inasmuch  as  the  more  they  are  examined  the 
less  competent  they  seem  to  explain  the  facts  observable  in  the 
terraced  valleys  of  New  England,  it  does  not  seem  worth  while 
to  give  them  more  explicit  consideration  here. 


532  PHYSIOGRAPHIC   ESSAYS 

Behavior  of  a  Wandering  River.  The  diagrams  introduced  in 
the  following  sections  represent  several  successive  stages  in  the 
process  of  slow  degradation  by  a  wandering  river.  The  postulates 
as  to  river  behavior  on  which  the  diagrams  are  based  are  (i) 
the  degrading  stream  continually  maintains  an  essentially  graded 
condition ;  (2)  the  lateral  swinging  of  the  meandering  channel 
is  very  much  faster  (a  hundredfold,  for  example)  than  the  degra- 
dation of  the  valley  floor ;  (3)  the  breadth  over  which  a  free 
river  (not  constrained  by  ledges)  tends  to  swing  laterally  is 
greater  than  the  breadth  of  the  meander  belt  (the  belt  included 
by  tangents  to  the  meandering  channel) ;  (4)  an  individual 
meander  tends  to  enlarge  its  radius  and  to  work  its  way  down 
the  valley  until  it  may  be  abandoned  at  season  of  high  water  for 
a  short-cut  across  a  flood-plain  lobe,  or  at  any  season  (but  usu- 
ally at  high  water)  for  a  cut-off  through  the  narrowing  neck  of 
a  lobe.  It  is  believed  that  abundant  justification  may  be  found 
for  all  these  postulates,  either  in  the  observed  behavior  of  a 
graded  river  or  in  the  success  with  which  they  lead  to  an  under- 
standing of  the  peculiar  patterns  of  our  terraces.  The  several 
postulates  may  now  be  reviewed. 

(i)  If  the  change  in  the  ratio  of  load  to  carrying  power  (vol- 
ume and  slope)  proceed  very  slowly,  a  river  may  remain  in  an 
essentially  graded  condition  all  through  the  process  of  aggrading 
or  of  degrading  its  valley,  and  through  the  change  from  aggrad- 
ing to  degrading.  It  is  true  that  the  graded  condition  depends 
on  a  balance  between  load  and  carrying  power,  and  it  would  at 
first  sight  appear  that  any  change  in  either  quantity  would  de- 
stroy the  balance  and  throw  the  river  out  of  grade.  But  if  the 
change  is  only  by  a  quantity  of  the  second  order,  —  that  is,  if 
either  load,  volume,  or  slope  is  changed  only  by  a  differential  of 
its  value  in  a  unit  of  time,  —  adjustment  to  the  new  condition 
will  follow  so  immediately  that  no  failure  of  adjustment  will  be 
noticeable.  A  similar  maintenance  of  an  essentially  graded  con- 
dition obtains  in  the  degradation  of  graded  (waste-covered)  hill- 
sides as  they  pass  from  maturity  to  old  age.  It  is,  however,  not 
likely  that  the  very  slow  degradation  of  a  valley  floor  which 
accompanies  the  advance  from  maturity  to  old  age  in  a  normal 
cycle  of  rock  erosion  will  result  in  terraces,  because  the  general 


RIVER  TERRACES  IN  NEW  ENGLAND  533 

processes  of  weathering  may  lower  the  flood  plain  about  as  fast 
as  the  river  sinks  to  a  fainter  and  fainter  slope.  The  rate  of 
degradation  of  a  terracing  river  in  a  drift-filled  valley,  resulting 
from  a  climatic  change  or  from  a  land  movement,  may  therefore 
be  allowed  a  decidedly  higher  value  than  that  of  an  aging  river 
in  a  normal,  undisturbed  cycle. 

(2)  It  is  well  understood  that  a  graded  stream  may  continue 
to  work   actively  in  wearing  or   building  its   banks    laterally, 
however  slowly   such  a  stream  aggrades  or  degrades  its  val- 
ley floor. 

(3)  There  are  abundant  examples  of  rivers  whose  lateral  oscil- 
lation or  swinging  carries  them  from  side  to  side  of  a  flood  plain 
that  is  much  wider  than  their  meander  belt.    The  Mississippi  is 
a  noted  case  of  this  kind.    Its  meander  belt  is  six  or  eight  miles 
wide  in  a  flood  plain  whose  inclosing  bluffs  are  from  twenty  to 
sixty  miles  apart.  A  similar  relation  may  be  seen  in  many  meadow 
flood  plains,  drained  by  small  brooks. 

(4)  The  fourth  postulate  involves  a  principle  of  river  action 
which  may  be  familiar  to  hydrographers,  but  which  is,  neverthe- 
less, not  commonly  stated.    Imagine  a  stream  in  a  broad  flood 
plain  passing  from  a  straight  stretch  or  tangent  to  a  well-defined 
curve.    On  the  tangent  AB  (Fig.  50),  the  thread  of  fastest  cur- 
rent might,  as  far  as  local  control  is  concerned,  lie  along  the 
middle  of  the  channel,  or  indifferently  on  one  side  or  other  of 
the  middle  line.    On  entering  the  curve  the  fastest  current  is 
gradually  shifted,  BC,  towards  the  outer  bank  of  the  channel, 
and  there  flowing  steadily  all  around  the  curve,  CZ>,  it  deter- 
mines the  line  of  greatest  depth.    On  passing  from  the  curve 
the  thread  of  fastest  current  is  necessarily  delivered  to  the  next 
downstream  tangent,  DE,  on  the  down-valley  side  of  the  channel, 
and  only  after  flowing  for  a  significant  distance  will  the  fastest 
current  gain  a  path  near  mid-channel.    If  the  curves  or  meanders 
are  close  set,  so  that  one  curve  passes  directly  into  the  next  one 
with  no  intervening  tangent,  then  the  thread  of  fastest  current 
must,  on  passing  the  point  of  inflexion,  enter  the  upstream  end 
of  the  next  curve  near  its  inner  or  convex  bank,  and  only  gradu- 
ally be  displaced  towards  the  outer  bank  as  inertia  has  time  to 
bring  about  its  usual  effect. 


534 


PHYSIOGRAPHIC  ESSAYS 


As  a  result  of  this  systematic  displacement  of  the  fastest  cur- 
rent from  the  mid-channel  line,  the  bank  that  it  approaches  will 
be  worn  away,  while  deposition  will  take  place  along  the  bank 
from  which  the  fast  current  is  withdrawn.  The  stream  will 
therefore  tend  to  wear  away  the  bank  on  the  outer  side  of  its 
curves  (but  perhaps  failing  to  begin  this  action  just  at  the 


FIG.  50 

beginning  of  the  curves)  and  on  the  down-valley  side  of  short 
tangents.  The  curves  will  thus  increase  in  radius  and  arc  and 
the  meander  belt  will  widen,  while  each  meander  will  tend  to 
move  slowly  down  'the  valley.  The  flood  plain  must  be  scoured 
out  for  a  certain  stretch  (NNf)  around  the  concave  banks  and 
along  the  up-valley  side  of  every  lobe,  while  a  scroll  of  new 
flood  plain  (MM)  is  added  around  the  end  and  on  the  down- 
valley  side  of  the  lobe. 


RIVER  TERRACES  IN  NEW  ENGLAND 


535 


All  this  may  be  easijy  recognized  in  the  meanders  of  a  meadow 
brook ;  and  that  it  occurs  even  in  the  Mississippi  is  abundantly 
illustrated  in  the  large-scale  maps  (three  inches  to  a  mile)  pub- 
lished by  the  Mississippi  River  Commission  (see  especially  sheets 
36,  38,  39),  where  the  lines  of  flood-plain  growth  pass  around 
the  end  and  along  the  down-valley  side  of  each  lobe,  while  they 
are  cut  across  by  the  encroaching  river  on  the  up-valley  side  of 
the  lobe,  as  indicated  in  Fig.  50.  Still  more  definite  proof  of  this 
feature  in  the  behavior  of  a  meandering  river  is  found  in  the 
new  edition  (1900)  of  the  Preliminary  Map  of  the  Mississippi 
(one  inch  to  a  mile),  in  which 
a  red  overprint  indicates  the 
new  position  of  the  channel, 
as  determined  some  fifteen 
years  after  the  previous  sur- 
vey (see  especially  sheets  14, 
1 6,  and  18). 

The  same  down-valley  shift- 
ing of  the  meanders  is  seen 
in  the  inclosed  meanders  of 
many  rivers,  typified  in  North 
Branch  of  the  Susquehanna 
(Fig.  51).  This  fine  river  has 
incised  its  course  beneath  the 
uplands  of  northern  Pennsyl- 
vania. The  upland  spurs  that  enter  the  river  curves  have  been 
subjected  on  their  up-valley  sides  to  a  persistent  sweeping  that  is 
but  little  less  effective  than  that  by  which  the  curved  reentrants 
between  the  spurs  have  been  scoured  out.  The  up-valley  side 
of  the  spurs  have  strong  bluffs,  as  different  from  their  gentle 
down-valley  slopes  as  are  the  high  lateral  bluffs  that  inclose 
the  curves  from  the  gentle  terminal  slopes  of  the  spurs.  It  is 
noteworthy  that  in  this  case  of  a  rock-walled  valley,  the  down- 
valley  shifting  of  the  curves  does  not  seem  to  have  been  more 
than  fifteen  or  twenty  times  greater  than  the  degrading  of  the 
river  channel  in  the  latest  period  of  valley  trenching ;  while  in 
the  case  of  terracing  streams  in  drift-filled  valleys,  the  first  of 
these  changes  exceeds  the  second  in  a  much  higher  degree.  It 


FIG.  51 


536  PHYSIOGRAPHIC  ESSAYS 

may  be  further  noted  that  the  North  Branch  of  the  Susque- 
hanna  above  Wilkesbarre  seems  for  some  time  past  to  have 
ceased  deepening  its  valley,  for  narrow  double-curved  scrolls  of 
flood  plain  are  now  systematically  added  to  the  outer  end  and 
the  down-valley  side  of  the  spurs,  as  may  be  especially  well 
seen  just  above  Tunkhannock,  and  as  is  indicated  by  the  dotted 
areas  MM\  opposite  the  under-cut  bluffs  NN'  (Fig.  51). 

Other  examples  of  meandering  valleys,  exhibiting  the  system- 
atic lateral  growth  and  down-valley  shifting  of  the  meander 
curves,  might  be  instanced  ;  a  few  of  them  are  mentioned  in 
my  paper  on  the  "  Drainage  of  Cuestas  "  (89).  It  is  my  hope  to 
give  at  another  time  a  fuller  account  of  this  phase  of  river 
development,  and  then  to  show  how  satisfactorily  the  stage  of 
development  may  be  stated  in  terms  of  the  flood-plain  pattern. 

The  four  postulates  above  announced  concerning  river  action 
may  therefore  be  taken  as  well  supported. 

A  natural  limit  is  set  to  the  dimensions  of  a  growing  meander 
curve  on  a  flood  plain  by  the  formation  of  short-cuts  across 
flood-plain  lobes  at  time  of  high  water,  or  of  cut-offs  when  the 
narrowing  neck  of  a  lobe  is  finally  worn  through,  a  roundabout 
course  being  in  both  cases  abandoned  for  a  more  direct  one.  It 
may  therefore  be  expected  that  the  abandoned  channels,  such 
as  are  preserved  in  ox-bow  lakes  on  existing  flood  plains,  and  in 
swampy  half-filled  channels  at  the  back  border  of  many  terraces, 
will  on  the  average  show  a  larger  radius  of  curvature  than  the 
curves  of  the  existing  river ;  and  the  maps  of  the  Mississippi 
give  some  support  to  this  expectation.  Emerson  has  pointed 
out  (735)  the  tendency  of  our  New  England  rivers  and  streams 
to  form  loops  or  ox-bows  on  the  right  of  their  general  course, 
from  which  they  return  to  a  nearly  direct  course  by  short-cuts 
or  cut-offs,  only  to  begin  again  the  work  of  right-handed  loop- 
cutting.  He  states  that  the  Connecticut  near  Northampton, 
Massachusetts,  has  seven  deserted  loops  on  the  right  (west) 
and  none  on  the  left ;  some  of  its  tributaries  have  sharp  bends 
and  oxbows  thirty  times  as  numerous  on  the.  right  as  on  the 
left  of  their  course.  It  is  naturally  suggested  that  this  asym- 
metry is  the  result  of  the  deflective  force  arising  from  the 
earth's  rotation. 


RIVER  TERRACES  IN  NEW  ENGLAND  .    537 

Terminology  of  Wandering  Rivers.  The  terms  already  intro- 
duced regarding  rivers  that  wander  about  their  flood  plains  may 
now  be  summarized  and  somewhat  extended.  The  space  inclosed 
between  tangents  drawn  outside  of  the  curves  or  meanders  of 
the  stream  is  the  meander  belt.  This  belt  will  widen  while  the 
meanders  are  normally  wearing  their  outer  bank ;  but  on  the 
occurrence  of  a  short-cut  across  a  flood-plain  lobe  or  of  a  cut- 
off through  the  narrowing  neck  of  a  lobe,  the  belt  will  locally 
collapse.  Here  the  river  course  becomes  relatively  direct  for  a 
time,  only  to  develop  serpentines  again  as  new  meanders  are 
established.  The  progressive  movement  of  the  meanders  down 
the  valley  will  be  called  sweeping.  Upstream  and  downstream 
will  be  used  in  their  ordinary  sense,  but  up-valley  and  down- 
valley  will  be  substituted  when  it  is  desired  to  indicate  a  more 
general  direction  than  that  of  the  circuitous  channel. 

The  lateral  movement  of  the  meander  belt  from  one  side  of 
the  valley  floor  to  the  other  will  be  referred  to  as  swinging.  It 
is  not  always  possible  to  distinguish  between  the  true  lateral 
swinging  of  the  meander  belt  as  a  whole  and  the  more  local 
shifting  of  an  irregularly  sweeping  meander.  The  compound 
movement  of  sweeping  meanders  in  a  swinging  meander  belt 
will  be  called  wandering,  this  term  being  fully  justified  when  it 
is  noted  that  many  unsystematic  irregularities  must  be  developed 
in  a  stream  channel,  whereby  it  will  depart  significantly  from 
the  simple  and  regular  movements  here  considered.  The  whole 
breadth  of  the  valley  floor  that  may  be  worn  down  by  the 
stream  will  be  called  the  belt  of  wandering ;  this  corresponds 
to  many  of  our  flood  plains  or  "  intervals." 

In  an  ideal  case,  a  regularly  growing  pattern  of  meander 
curves  might  be  imagined  slowly  sweeping  down  a  valley,  the 
meander  belt  collapsing  here  and  there,  now  and  then,  but 
growing  again  to  its  ordinary  breadth  as  new  curves  are 
developed  in  the  place  of  the  old  ones.  At  any  point  in  the 
valley  an  endless  procession  of  meanders  would  sweep  past. 

If  it  be  now  supposed  that  the  wandering  stream  is  slowly  de- 
grading its  valley  floor,  each  meander  will  sweep  past  a  given 
point  at  a  slightly  lower  level  than  that  of  its  predecessor ; 
and  each  time  the  meander  belt  swings  across  the  valley  from 


538 


PHYSIOGRAPHIC  ESSAYS 


one  side  to  the  other  and  back  again,  it  will  return  at  a  dis- 
tinctly lower  level  than  that  at  which  it  left.  The  flood  plains 
formed  at  different  stages  of  this  leisurely  process  will  differ  in 
altitude,  and  all  of  them  will  be  inclined  gently  down  the 
valley.  It  is  the  remnants  of  these  flood  plains  that  form  our 
terrace  plains. 

Ideal  Terrace  Patterns :  Early  Stage.  Soon  after  the  stage 
of  degradation  has  been  definitely  established  and  the  meander- 
ing stream  begins  to  swing  across  the  valley  at  a  little  lower 
level  than  before,  a  condition  represented  in  Fig.  52  may  be 


FIG.  52 

reached.  In  this  figure,  as  in  a  number  that  follow,  it  is  sup- 
posed that  the  view  is  taken  from  a  considerable  height,  look- 
ing northwest  across  the  valley  of  a  south-flowing  river.  The 
terrace  plains  are  left  blank  in  most  of  the  diagrams.  The 
western  meander  in  the  foreground  of  I^ig.  52  is  now  scouring 
out  a  curve  in  a  low  concave  terrace  scarp  (B),  the  ninth  of  its 
kind  within  the  limits  of  the  diagram.  A  small  portion  of  a 
terrace  (A),  of  slightly  less  height,  is  shown  in  the  immediate 
foreground  ;  it  may  represent  the  work  of  the  preceding  west- 
ward meander,  while  the  next  following  westward  meander  is 
cutting  out  a  deeper  terrace  (C),  in  the  background.  Terrace  A 
may  be  taken  as  one  of  the  first  marks  made  by  the  degrading 
stream.  Terrace  B  is  of  greater  height  than  A  because  A  has 


RIVER  TERRACES  IN  NEW  ENGLAND 


539 


s 


been  under-cut  and  consumed  in  the  production  of  B,  except  in 
the  immediate  foreground.  Terrace  C  is  as  yet  independent  of 
B,  and  therefore  shows  a  height  to  be  measured  only  by  the 
few  inches  or  feet  of  depth  to  which  one  sweeping  meander  cuts 
below  the  plain  of  its  predecessor.  The  curves  and  cusps  of 
terrace  B  result  from  a  vacillation  of  the  meander  during  its 
down- valley  progress  ;  a  rather  sharp  cusp  being  left  between  B* 
and  Bz,  while  the  curves  from  B*  to  B9  have  arcs  so  small  as  to 
join  in  an  early  straight  terrace  front. 

It  may  be  noted  that  the  small 
curves  by  which  a  nearly  straight 
terrace  front  is  usually  formed  are 
as  a  rule  to  be  expected  only  towards 
the  side  of  a  valley,  and  less  com- 
monly on  a  terrace  spur  that  advances 
into  the  valley.  For  example,  in  Fig. 
53  the  little  curves  A,  C,  Z>,  E  record 
so  many  positions  of  the  meander 
apex,  and  will  not  now  be  destroyed 
until  a  later  meander  under-cuts  them. 
Scarps  of  this  kind  may  be  called  one- 
sweep  scarps  ;  and  their  cusps,  one- 
sweep  cusps.  Several  similar  cusps 
are  shown  in  Fig.  52.  The  longer 
curve  EE\  cut  by  the  advancing  front 
of  the  meandering  river,  may  be  abandoned  if  the  river  is  diverted 
by  a  short-cut  to  a  new  course,  and  if  so,  the  advancing  terrace 
spur  will  be  smooth  trimmed. 

A  terrace  whose  scarp  has  been  almost  evenly  trimmed  by 
the  small  vacillations  of  a  down-sweeping  meander  will  face  the 
axis  of  the  valley.  A  terrace  whose  scarp  has  been  under-cut 
by  the  forward  half  of  a  down-sweeping  meander  will  face  ob- 
liquely up  the  valley,  as  in  the  foreground  of  Fig.  53.  Inasmuch 
as  the  normal  progress  of  meander-sweeping  is  down  the  valley, 
it  would  seem,  at  first  thought,  that  no  terrace  scarps  could  be 
carved  so  as  to  face  in  that  direction ;  but  on  second  thought  it 
will  be  seen  that  the  lateral  growth  of  a  meander  may  cause 
part  of  the  curve  to  grow  up-valley  faster  than  the  meander  is 


FIG. 53 


540 


PHYSIOGRAPHIC  ESSAYS 


carried  in  the  other  direction  by  the  normal  down-valley  sweep- 
ing of  the  meander  system;  and  in  this  case  a  terrace  scarp 
facing  obliquely  down-valley  will  be  carved.  An  example  of 
this  kind  is  shown  near  the  foreground  of  Fig.  54.  It  is  mani- 
fest that  the  development  of  terraces  facing  down-valley  will 
be  favored  wherever  the  down-valley  sweeping  of  a  group  of 
meanders  is  for  any  reason  checked  while  the  enlargement  of 
their  curves  is  continued. 

There  can  be  little  doubt  that  the  height  of  terraces  pro- 
duced by  the  action  of  successive  meanders  would  be  very 
small,  hardly  measuring  as  many  inches  or  quarter  inches  as 


FIG.  54 

actual  terraces  measure  in  feet.  Let  it  therefore  be  now  sup- 
posed that  after  a  series  of  one-sweep  scarps  has  been  carved, 
the  river  swings  away  from  the  western  side  of  its  valley  and 
for  a  time  occupies  itself  in  carving  scarps  on  the  eastern  side. 
Many  meanders  will  have  swept  down  the  valley  during  the 
eastward  swing  of  the  meander  belt,  each  meander  leaving  its 
faint  scar  on  the  valley  floor.  When  the  river  swings  westward 
again,  it  will  be  working  at  a  lower  level  than  before,  and  as  it 
then  once  more  under-cuts  the  high  plain,  a  distinct  terrace  with 
a  scarp  of  ten  or  twenty  feet  will  be  formed.  Terraces  of  dis- 
tinctly different  levels  may  therefore  usually  be  taken  to  repre- 
sent different  swings  of  the  meander  belt ;  terraces  that  represent 
only  the  sweeps  of  successive  meanders  while  the  belt  remains 
almost  stationary  must  be  so  faint  as  to  be  hardly  noticeable. 


RIVER  TERRACES  IN  NEW  ENGLAND  541 

A  cusp  which  results  from  the  slightly  vacillating  forward 
sweep  of  a  single  meander,  as  B*,  B1 ',  etc.  (Fig.  52),  has  al- 
ready been  called  a  one-sweep  cusp.  The  terrace  plain  extend- 
ing forward  from  the  base  of  such  a  cusp  will  be  a  smoothly 
continuous  surface  on  both  sides  of  the  apex.  When  the  two 
parts  of  a  terrace  plain  on  either  side  of  a  cusp  differ  in  height 
by  a  foot  or  two,  they  are  probably  the  product  of  different 
(but  not  necessarily  successive)  meanders ;  and  such  a  cusp 
may  be  called  a  two-sweep  cusp,  because  the  two  levels  prob- 
ably represent  different  sweeps  -in  the  meander  belt.  When  the 
difference  in  height  is  a  number  of  feet,  the  cusp  is  probably  a 
two-swing  cusp,  because  the  two  levels  are  then  best  explained 
by  different  (but  not  necessarily  successive)  swings  of  the  meander 
belt.  Examples  of  the  forms  described  above  are  frequently 
observed. 

Ideal  Terrace  Pattern:  Middle  Stage.  If  the  sweeping  and 
swinging  of  the  river  continue  until,  as  in  Fig.  54,  a  fifth  return 
of  the  meander  belt  to  the  western  side  of  the  valley  is  ac- 
complished, a  terrace  pattern  of  some  complication  may  result. 
Few  and  small  remnants  of  the  higher  terrace  plains  are  to  be 
expected  at  this  stage,  for  they  have  been  repeatedly  under- 
cut and  destroyed.  Larger  and  more  numerous  remnants  of 
the  lower  plains  may  be  still  preserved,  for  they  have  been  less 
frequently  attacked.  A  triangular  portion  of  the  third-swing 
plain  is  shown  in  the  middle  of  the  figure ;  on  the  right 
appears  a  still  larger  piece  of  the  fourth-swing  plain,  from 
which  the  river  was  withdrawn  by  a  short-cut  across  the  flood 
plain  (not  shown  in  the  figure),  leaving  an  unfilled  channel 
which  now  guides  a  small  brook.  The  fifth  westward  swing  of 
the  river  has,  during  the  down-valley  sweep  of  a  single  meander 
over  the  length  of  the  diagram,  under-cut  and  destroyed  part  of 
the  fourth-swing  plain  on  the  right ;  it  has  destroyed  all  of  the 
fourth-swing  and  part  of  the  third-swing  plain  in  the  middle 
and  all  of  the  earlier  plains  toward  the  left,  where  the  meander 
under-cuts  the  high  scarp  and  recent  landslips  have  occurred. 
The  greater  the  number  of  swings,  the  smaller  and  rarer  will 
be  the  remnants  of  the  higher  terrace  plains,  unless  some  special 
control  is  present  to  preserve  them. 


542  PHYSIOGRAPHIC  ESSAYS 

A  special  interest  attaches  to  the  form  and  arrangement  of 
the  cusps  that  are  produced  by  the  chance  intersection  of  the 
curved  terrace  fronts.  In  the  two-sweep  or  two-swing  cusps, 
two  patterns  may  be  produced,  according  as  the  higher  scarp  is 
on  the  up-valley  or  down-valley  side  of  the  cusp,  as  in  Figs. 
55  and  56.  The  higher  scarp  is  evidently  the  younger  of  the 
two  that  unite  in  the  cusp ;  it  is  continued  in  direction,  but 
with  less  height  beyond  the  point  of  intersection.  From  the 
appearance  of  a  letter  Y  in  the  shaded  scarps  of  the  diagrams 
forms  of  this  kind  may  be  called  two-swing  (or  two-sweep) 
cusps,  with  an  upstream  or  a  downstream  Y-stem,  as  the  case 
may  be.  All  the  elements  of  such  cusps  are  variable.  The 
location  of  the  cusp  is  at  the  chance  intersection  of  two  lines 


FIG.  55  FIG.  56 

that  have  no  particular  relation  to  each  other.  The  angle  of  the 
Y  may  vary  through  a  large  range.  The  heights  of  the  scarps 
have  no  definite  relation,  except  that  the  higher  single  scarp 
must  be  the  sum  of  the  other  two. 

A  series  of  one-sweep  cusps  may  occur  with  some  regularity 
along  a  valley  side,  but  two-sweep  and  two-swing  cusps  cannot 
be  expected  to  show  so  definite  an  arrangement,  unless  under  the 
control  of  something  more  systematic  than  the  action  of  the  wan- 
dering stream.  In  Fig.  54,  for  example,  two  series  of  one-sweep 
cusps  in  the  middle  of  the  diagram  stand  in  normal  down-the- 
valley  order,  but  all  the  two-swing  cusps  are  located  indifferently 
to  one  another.  So  on  the  left  side  of  Fig.  49 ;  but  on  the  right 
side  of  that  figure,  three  one-sweep  cusps  on  successive  terraces 
are  placed  in  line,  one  forward  of  the  other,  as  if  in  some  way 
systematically  related  or  subject  to  some  common  control. 


RIVER  TERRACES  IN  NEW  ENGLAND  543 

In  view  of  these  various  ideal  combinations,  it  is  evidently 
desirable  to  analyze  the  special  configurations  that  may  be  due 
to  river  action  alone,  in  order  to  detect  more  surely  the  patterns 
that  must  be  referred  to  some  other  cause. 

A  later-made  one-sweep  cusp  may  occasionally  chance  to 
stand  in  front  of  an  earlier-made  one-sweep  cusp,  as  in  the 


FIG.  57  FIG.  58 

farther  part  of  Fig.  57;  but  it  is  evidently  out  of  the  ques- 
tion that  four  cusps  should  gain  a  systematic  position  of  this 
kind,  as  in  the  center  of  Fig.  58,  without  some  common 
control.  Whenever  such  arrangement  is  found,  special  exami- 
nation should  be  made  of  it.  Again,  while  a  two-swing  cusp  is 
of  common  occurrence,  a  three-swing  cusp  (Fig.  59)  must  be 
rare,  for  it  involves  the  intersection  of  three  unrelated  lines 


FIG.  59  FIG.  60 

in  a  systematic  manner ;  and  a  four-swing  cusp  (Fig.  60)  is 
practically  an  impossible  occurrence.  True,  a  three-swing  cusp 
must  be  produced  at  a  certain  stage  of  the  change  shown  in 
Fig.  61,  where  a  sweeping  meander  is  under-cutting  its  scarp 
and  thus  pushing  one  two-swing  cusp,  A,  towards  another  two- 
swing  cusp,  B ;  for  at  a  certain  stage  in  the  under-cutting,  A 


544 


PHYSIOGRAPHIC  ESSAYS 


will  be  pushed  into  coincidence  with  B,  thus  forming  a  three- 
swing  cusp.  But  it  is  very  improbable  that  this  temporary 
stage  will  be  preserved.  The  under-cutting  will  continue  and 
the  temporary  three-swing  cusp  will  then  be  divided  into  two 


FIG.  61 


FIG.  62 


two-swing  cusps,  C  and  D.  The  three-swing  cusp  can  be  pre- 
served only  when,  just  at  the  moment  of  its  formation,  the 
stream  is  withdrawn  by  a  short-cut  or  a  cut-off,  and  such  a 
coincidence  must  be  of  very  rare  occurrence.  Withdrawals  of 
the  stream  may,  however,  happen  likely  enough  before  or  after 
the  momentary  stage  of  the  three-swing  cusp ;  and  the  various 
patterns  thus  producible  are  indicated  by  the  full  and  broken 
lines  in  Figs.  61-64.  The  eight  possible  cases  of  this  kind 
result  from  different  combinations  of  the  up-valley  or  down- 
valley  half  of  a  meander  with  two-swing  cusps  of  upstream 


FIG.  63 


FIG.  64 


or  downstream  Y-stems.  Evidently,  then,  no  combination  of 
unguided  sweeping  and  swinging  meanders  will  produce  an 
orderly  grouping  of  cusps  such  as  is  shown  in  Fig.  58. 

Ideal  Terrace  Patterns :  Late  Stage.   When  the  causes  that  de- 
termine the  degradation  of  a  valley  floor  weaken  and  disappear, 


RIVER  TERRACES  IN  NEW  ENGLAND 


545 


the  stream  will  repeatedly  swing  to  and  fro  on  about  the  same 
plane.  Even  the  basal  terraces  of  a  series  may  then  be  almost 
completely  swept  away  by  the  wandering  river,  as  in  Fig.  65, 
and  the  whole  descent  from  the  high-level  terrace  to  the  ex- 
isting flood  plain  may  be,  for  considerable  distances  along  the 
valley  side,  united  in  a  single  strong  escarpment.  The  conditions 
under  which  this  result  may  be  brought  about  are  first,  the 
attainment  of  nearly  fixed  values  of  volume  and  load,  such  as 
might  be  reached  when  a  glacial  climate  had  given  way  to  a 
milder  climate  and  the  latter  had  become  well  established  ;  sec- 
ond, the  cessation  of  any  slow  uplift  by  which  degradation  had 


FIG.  65 

been  initiated  or  aided  ;  third,  superposition  of  the  stream  on  a 
strong  rock  sill  on  which  corrasion  is  very  slow.  Under  these 
conditions  a  stream  would  almost  cease  to  degrade  its  channel, 
and  would  then  devote  practically  all  its  energy  to  lateral  cutting. 
The  stream  would  wander  back  and  forth  across  its  valley  floor, 
unimpeded  save  by  its  flood-plain  bank,  until  it  came  against  a 
lateral  terrace ;  and  the  terrace  would  be  worn  back  to  the  limit 
of  the  belt  of  wandering.  Sooner  or  later  the  stream  would  con- 
sume all  the  high-level  and  intermediate  terraces,  pushing  back 
their  united  scarps  into  a  single  scarp,  by  which  the  highest  ter- 
race plain  would  then  descend  at  once  to  the  flood  plain.  Stepping 
terraces  would  no  longer  characterize  this  stage  of  valley  devel- 
opment, but  a  few  low  terraces  might  remain  not  yet  consumed 
here  and  there,  as  in  Fig.  45. 


546  PHYSIOGRAPHIC  ESSAYS' 

Miller  seems  to  suggest  that  an  increase  in  the  height  of  ter- 
race scarps  is  in  itself  a  cause  for  a  decrease  in  interscarp  space. 

The  restraint  exercised  by  rock  upon  the  modern  rivers  strengthens  their 
natural  tendency,  of  which  sufficient  account  has  not  been  made,  to  occupy 
narrower  portions  of  valleys  the  more  they  deepen  them.  It  has  been  too 
hastily  concluded,  because  rivers  now  occupy  narrow  valleys  flanked  by 
terraces  comparatively  broad,  that  therefore  they  have  vastly  shrunk, — 
from  dimensions,  in  fact,  proportional  to  the  greater  breadth  (299). 

He  then  goes  on  with  the  statement  already  quoted  regarding 
the  "banks  nowadays  eight  or  ten  times  as  high."  as  formerly. 
It  thus  seems  to  be  implied  that  it  is  "natural"  for  the  inter- 
scarp  space  of  a  stream  of  constant  value  to  lose  width  ;  and  that 
not  only  rock  ledges  restrain  the  breadth  of  the  belt  of  wander- 
ing, but  that  the  increase  in  height  of  the  inclosing  scarps  also 
has  a  share  in  determining  this  feature  of  valley  form.  A  similar 
opinion  is  expressed  by  Gilbert  (133).  This  seems  to  me  an  un- 
necessary conclusion,  unless  rapid  elevation  up  to  a  recent  date 
be  postulated  also,  as  is  perhaps  implied  by  Miller  in  a  later 
sentence.  Certainly,  so  far  as  increase  of  scarp  height  in  New 
England  valleys  is  concerned,  it  has  not  sufficed  to  prevent  the 
broadening  of  the  valley  floor  and  the  consumption  of  terraces 
at  higher  levels,  so  long  as  the  terraces  consist  only  of  clay,  sand, 
and  gravel. 

It  may  be  noted  that  if  there  had  been  a  diminution  of  volume 
during  the  deepening  of  a  drift-filled  valley,  the  obliteration  of 
stepping  terraces  would  be  delayed,  but  not  prevented.  It  has 
already  been  explained  that  some  diminution  in  stream  volume 
is  certainly  probable.  It  may  now  be  added  that  many  valleys 
have,  in  spite  of  this  very  probable  decrease  of  stream  volume, 
already  reached  in  one  or  another  part  of  their  length  the  late 
stage  of  terracing  just  described,  in  which  all  the  descent  from 
the  highest  terrace  to  the  flood  plain  is  concentrated  in  a  single 
scarp,  and  that  in  many  other  parts  of  these  valleys  only  a  few 
basal  terraces  remain  beneath  the  strong  scarp  of  the  high  ter- 
race. It  thus  becomes  all  the  more  probable  that  diminution  of 
volume  is  not  an  important  cause  of  the  decrease  in  the  breadth 
of  the  interscarp  space,  and  that  where  stepping  terraces  occur, 
they  must  be  in  large  part  referred  to  some  special  and  local 


RIVER  TERRACES  IN  NEW  ENGLAND 


547 


cause.  Such  a  cause  is  found  in  the  presence  of  rock  ledges, 
as  suggested  by  Miller ;  and  to  that  element  of  the  problem  we 
may  now  turn. 

Defended  Terrace  Cusps :  Early  Stage.  Itjias  thus  far  been 
tacitly  postulated  that  no  buried  ledges  should  be  discovered 
by  the  wandering  river.  'Siich,  indeed,  is"  fhe  condition  usually 
assumed  in  the  cross  section  of  a  series  of  typical  terraces,  as  in 
Fig.  44.  Let  a  new  series  of  terraces  now  be  developed,  in  which 
ledges  shall  here  and  there  be  discovered  as  the  river  degrades 
its  valley  floor  to  greater  and  greater  depths.  It  is  evident  that 
the  number  of  such  ledges  may  vary  greatly.  They  might  be 


FIG.  66 

numerous  and  frequently  encountered  by  a  terracing  river  in  a 
narrow  valley  with  rugged  rock  walls  and  bottom ;  they  might 
be  almost  absent  and  hardly  ever  discovered  in  a  broad  valley 
that  had  been  heavily  aggraded.  In  all  cases  it  is  important  to 
note  that  the  slope  of  a  ledge  face  will  seldom  be  as  steep  as  the 
average  slope  of  a  terrace  front,  which  may  be  as  much  as  30° 
in  freshly  cut  scarps. 

As  before,  the  river  wanders  about  freely  so  long  as  it  is 
working  on  unconsolidated  sands  and  clays  ;  and  thus  several 
low  terraces  may  be  formed  in  the  manner  already  described. 
But  when  a  ledge  is  encountered  in  the  river  bank,  as  at  the  left 
forward  edge  of  Fig.  66,  the  rock  is  practically  indestructible. 
The  stream  will  in  a  comparatively  short  time  swing  away,  after 


548 


PHYSIOGRAPHIC  ESSAYS 


having  altered  its  course  more  or  less  in  a  fruitless  effort  to  wear 
back  the  obstacle.  The  ledge  thus  comes  to  determine  a  cusp 
in  the  terrace  front.  A  salient  of  this  kind  may  be  called  a  de- 
fended cusp,  in  distinction  from  the  accidental  or  free  cusps 
described  in  the  previous  sections ;  the  terrace  behind  it  cannot 
be  destroyed  by  the  stream. 

Following  the  colloquial  style  often  adopted  for  field  descrip- 
tions, a  terrace  of  this  kind  is  sometimes  entered  in  my  notes  as  a 
"can't-be,"  in  contrast  to  the  low  "not-yet"  terraces  of  Fig.  65. 

It  should  be  noted  that  the  ledge  here  considered  does  not 
determine  the  depth  to  which  the  river  may  work ;  the  rock  is 


FIG.  67 

exposed  only  in  the  river  bank  and  enters  but  a  little  distance 
into  the  channel.  The  slope  of  the  river  and  the  depth  to  which 
it  has  cut  at  this  or  any  other  point  in  its  course  are  assumed  to 
be  determined  in  all  cases  thus  far  detailed  by  the  maintenance 
of  an  essentially  graded  channel  with  respect  to  some  controlling 
base-level  farther  downstream ;  the  sea  at  the  river  mouth,  a 
larger  river  into  which  the  smaller  stream  enters,  or  a  broad  sill 
of  rock  that  stretches  all  across  the  channel,  somewhere  farther 
down  the  valley. 

When  the  withdrawing  stream  swings  back  again  at  a  lower 
level,  as  in  Fig.  67,  it  cannot  often  under-cut  and  destroy  all  of 
the  terrace  on  whose  back  border  the  first  ledge  rises,  because, 
as  has  been  noted,  the  slope  of  the  ledge  is  seldom  so  steep  as 


RIVER  TERRACES  IN  NEW  ENGLAND 


549 


that  of  the  terrace  scarp.  A  second  encounter  with  the  ledge 
will  usually  be  made  before  the  swinging  stream  has  entirely 
consumed  the  terrace  of  the  previous  swing.  Every  return  of 
the  swinging  river  against  a  sloping  reef  of  rocks  will  thus  be 
recorded  by  a  little  strip  of  terrace  behind  the  defending  ledges, 
and  a  flight  of  stepping  terraces  will  necessarily  be  produced 
wherever  a  large  group  of  ledges  slopes  under  the  valley  drift 
into  the  belt  of  river  action.  The  length  of  the  ledge  exposed  at 
the  back  of  each  terrace  may  be  but  a  few  feet,  but  its  effect  will 
be  prolonged  by  a  trailing  terrace,  as  it  may  be  called,  stretch- 
ing hundreds  or  thousands  of  feet  along  the  valley  side.  It  is  in 
this  way  that  the  best  flights  of  stepping  terraces  are  produced. 


FIG.  68 


FIG.  69 


The  special  features  of  terraces  associated  with  defending 
ledges  are  next  to  be  examined. 

Slipping  Meanders  and  B hint  Cusps.  It  has  not  yet  been  pos- 
sible to  discover  by  observation  how  a  down-sweeping  meander 
will  make  its  passage  past  a  ledge,  but  it  may  be  inferred  from 
the  forms  of  terraces  found  in  various  valleys  that  a  stream  has 
two  methods  of  procedure  in  such  an  exigency.  The  first  is  con- 
sidered in  this  section,  and  is  illustrated  in  Figs.  68-71  ;  the 
second  is  taken  up  in  the  next  section,  with  Figs.  72-74. 

Let  it  be  supposed  that  the  river  in  Fig.  68  is  now  making 
its  fourth  swing  against  the  western  side  of  its  valley,  and  that 
a  buried  ledge  lies  a  few  hundred  feet  back  of  the  group  of  free 
cusps  in  the  middle  of  the  diagram.  The  ledge  is  discovered  in 
Fig.  69 ;  it  lies  somewhat  below  the  apex  of  a  down-sweeping 
meander.  Assuming  that  the  meander  curve  is  to  remain  prac- 
tically unchanged,  it  can  pass  the  ledge  only  by  withdrawing 


550 


PHYSIOGRAPHIC  ESSAYS 


somewhat  towards  the  axis  of  the  valley;  it  may  thus,  as  it  were, 
slip  by  the  obstacle  that  stands  immovable  in  its  way.  The  stream 
is  represented  as  having  just  slipped  past  the  ledge  in  Fig.  70, 
and  as  having  swept  somewhat  farther  down  the  valley  in  Fig. 
71*  All  records  of  the  first  and  third  swing  of  the  river  are  now 
destroyed,  so  far  as  this  part  of  the  valley  is  concerned  ;  the 
terrace  front  shows  a  high,  defended,  one-sweep  cusp,  a  free  two- 
sweep  cusp  with  an  upstream  Y-stem,  and  a  free  one-sweep  cusp. 
The  ledge  at  the  base  of  the  defended  cusp  may  come  to  be 
more  or  less  concealed  by  the  sands  that  are  washed  down  from 
the  weathering  scarp.  In  time  it  may  be  entirely  covered,  and 
its  presence  will  then  be  known  only  if  a  roadcut  or  a  boring 
reveals  it.  It  is  therefore  quite  possible  that  some  apparently 


FIG.  70 


FIG. 71 


free  cusps  are  really  defended  cusps,  with  their  defending  ledge 
ambushed  beneath  a  thin  cover  of  soil. 

Compressed  Meanders  and  Sharp  Cusps.  Let  it  now  be  sup- 
posed that  the  river  in  Fig.  69  is  unable  to  slip  past  the  ledge. 
The  front  of  the  curve  is  held  fast ;  the  apex  of  the  curve  bends 
outward  and  cuts  a  curved  reentrant  in  the  terrace  front  next 
upstream  from  the  ledge,  as  in  Fig.  72.  The  meanders  farther 
upstream  continue  their  advance,  and  the  meander  next  to  the 
ledge  is  therefore  compressed  to  a  relatively  strong  curvature, 
as  in  Fig.  73.  The  defended  cusp  is  now  sharpened.  It  may 
come  to  point  somewhat  up  the  valley.  The  compressed  meander 
cannot  slip  by  the  ledge ;  there  is  no  escape  for  the  stream  save 
by  a  short-cut  across  the  narrowing  flood-plain  lobe  at  time  of 
high,  water ;  thus  the  condition  of  Fig.  74  will  in  due  time  be 
developed.  A  rather  sharp  cusp,  one  of  whose  sides  faces  up 


RIVER  TERRACES  IN   NEW  ENGLAND 


551 


the  Valley,  will  be  produced,  and  the  great  concave  scarp  adja- 
cent to  it  will  have  an  abandoned  channel  at  its  base. 

Terrace  Fronts  near  Defended  Cusps.  The  difference  between 
the  behavior  of  slipping  and  of  compressed  meanders  may  be 
inferred  to  depend  on  the  position  of  the  obstructing  ledge 
with  regard  to  the  apex  of  the  meander.  If  the  ledge  is  discov- 
ered near  the  apex  of  the  meander,  the  stream  may  slip  past 
the  obstacle,  as  in  the  example  first  given.  If  the  ledge  is 


FIG.  74 


FIG.  72  FIG.  73 

encountered  near  the  point  of 
river  inflexion,  —  that  is,  on  the 
tangent  between  two  meanders, 
—  compression  of  the  meander 
upstream  from  the  obstacle  is 
likely  to  result. 

In  both  these  cases  the  de- 
fended cusp  is  likely  to  be  asso- 
ciated with  several  short  curves 
and  free  blunt  cusps  for  a  little 
distance  down-valley,  while  a  rather  long  reentrant  curve  usually 
joins  its  up-valley  side.  The  short  curves  and  blunt  cusps  may 
be  blended  so  as  to  produce  a  convex  terrace  front  for  a  little 
distance  down-valley  from  the  ledge  ;  and  this  convex  front  will 
be  separated  from  the  long  concave  reentrant  by  a  more  or  less 
pronounced  angle  at  the  defended  cusp.  The  reason  of  this  may 
be  easily  understood  from  Fig.  75.  The  ledge  was  here  first  dis- 
covered by  a  down-sweeping  meander,  of  whose  first  work  only 
the  short  scarp  A  remains.  The  meander  was  then  compressed 
so  as  to  scour  out  a  large  concave  reentrant,  and  was  withdrawn 


552 


PHYSIOGRAPHIC  ESSAYS 


from  the  channel  B  at  its  base  by  a  short-cut  (outside  of  the 
diagram).  A  meander  on  the  new  course  of  the  stream,  swinging 
westward,  trimmed  off  the  terrace  front  in  successive  lines, 
C,D,E\  but  as  this  meander  had  no  definite  relation  to  the 
ledge,  and  as  the  general  sweeping  of  its  curve  was  down-valley, 
it  did  not  trim  the  terrace  front  with  any  special  regard  to  the 
down-valley  side  of  the  defending  ledge.  In  brief,  the  tendency 
of  a  stream  to  sweep  its  meanders  down-valley  commonly  results 
in  trimming  off  the  terrace  front  close  to  the  up-valley  side  of  a 
defending  ledge,  but  it  is  only  by  chance  that  the  terrace  is  worn 


FIG.  75 

away  close  on  the  down-valley  side  of  the  ledge.    The  pattern 
here  deduced  may  be  matched  in  many  actual  examples. 

Defended  Cusps  :  Later  Stage.  After  a  ledge  has  once  been 
discovered  by  the  swinging  river,  there  is  much  probability  that 
the  forward  reach  of  its  under-slope  will  present  an  obstruction 
to  the  stream  every  time  it  swings  again  towards  the  valley  side. 
For  example,  let  the  stream  of  Fig.  74  be  supposed  to  have 
returned  from  a  swing  to  the  eastern  side  of  its  valley  floor.  It 
will  now  be  at  a  lower  level  than  before  and  will  therefore  be 
halted  somewhat  in  advance  of  the  defended  cusp  previously 
developed.  Fig.  76  shows  the  blunt  cusp  of  a  slipping  meander 
thus  determined.  Another  swing  out  and  back  having  been  ac- 
complished, Fig.  77  shows  the  work  of  a  compressed  meander  (A), 


RIVER  TERRACES  IN  NEW  ENGLAND 


553 


which  for  a  time  was  held  up-valley  from  a  third  exposure  of  the 
long-sloping  ledge ;  but  the  stream  was  then  withdrawn  from  its 
roundabout  course  by  a  short-cut,  after  which  a  sweeping  meander 
wore  out  the  three  short  curves  (£)  down-valley  from  the  ledge ; 
and  still  later,  the  next  down-sweeping  meander  (C)  trimmed  off 
the  terrace  front  close  to  the  ledge  preparatory  to  slipping  past 
the  obstacle  and  pushing  still  farther  back  the  down-valley  side 
of  the  terrace  front.  Another  stage  is  shown  in  Fig.  78.  Here 


FIG. 78 


FIG.  76  FIG.  77 

the  eighth  westward  swing  of  the 
stream  is  recorded  (compare  Fig. 
68).  Part  of  the  plain  formed  by 
the  second  swing  happens  to  be 
still  preserved,  but  not  of  the  first 
and  third.  All  the  later  swings, 
fourth  to  eighth,  are  well  indi- 
cated. A  strongly  compressed 
meander  of  the  eighth  swing  has 
trimmed  off  all  the  terraces  a  little  distance  up-valley  from  their 
ledges,  and  would  have  trimmed  them  still  closer  but  for  being 
withdrawn  by  a  short-cut.  A  later  meander  of  the  same  swing 
is  less  successfully  wearing  away  the  down-valley  extension  of 
the  terraces. 

It  is  evident  that  an  infinite  variety  of  terrace  patterns  may  be 
expected  in  association  with  defending  ledges,  yet  they  must  all 
conform  to  certain  general  laws  of  development. 

If  the  ledge  lies  at  a  low  level,  the  greater  part  of  the  terraces 
that  have  been  cut  at  swings  of  higher  level  will  have  been  de- 
stroyed before  the  ledge  has  a  chance  to  defend  them.  If  the 


554  PHYSIOGRAPHIC  ESSAYS 

ledge  is  of  large  size,  rising  nearly  to  the  highest  terrace  level 
and  standing  forward  in  such  a  position  that  the  stream  may  fre- 
quently swing  against  its  buried  slope,  a  whole  flight  of  stepping 
terraces  may  be  not  only  formed  but  preserved  by  it.  Here  the 
early  terraces,  unlike  those  of  free-swinging  rivers,  are  defended 
by  ledges,  and  cannot  be  attacked  by  the  later  swings  and 
sweeps  of  the  stream.  They  are  subject  to  destruction  only  by 
general  weathering  and  washing  of  the  valley  sides.  It  is  evi- 
dently, then,  to  the  largest  and  highest  and  most  outstanding 
ledges  that  one  must  go  in  order  to  find  the  fullest  record  of  the 
number  of  swings  that  a  river  has  executed  during  the  excavation 
of  its  valley,  for  only  on  such  ledges  are  the  records  of  river 
terracing  well  preserved.  Elsewhere  they  are  for  the  most  part 
swept  away.  Even  here  some  swings  may  not  be  recorded.  In 
short,  the  maximum  number  of  terraces  shows  only  the  minimum 
number  of  river  swings. 

Diminished  Swinging  of  the  Meander  Belt.  The  greater  the 
depth  to  which  the  valley  floor  is  degraded,  the  more  frequently 
may  ledges  be  found,  and,  as  a  rule,  the  nearer  will  they  stand 
to  the  axis  of  the  valley.  The  number  of  defended  cusps  will 
therefore  tend  to  increase  as  the  valley  deepens.  The  breadth 
of  free  swinging  will  at  the  same  time  decrease,  and  the  space 
between  the  scarps  of  the  lower  terraces  will  necessarily  be  less 
than  the  space  between  the  higher  terraces.  This  principle,  first 
stated  by  Miller,  seems  to  be  essential  in  explaining  the  stepping 
terraces  of  New  England. 

It  must  frequently  happen  that  ledges  approach  the  axis  of  a 
valley  more  closely  at  one  point  than  at  another.  The  valley  may 
be  well  beset  with  buried  reefs  for  a  fraction  of  a  mile  or  more, 
and  then  may  be  relatively  free  from  ledges  for  several  miles  up 
and  down  stream.  Where  the  ledges  are  numerous,  the  valley 
will  be  narrowed  and  the  terraces  will  be  preserved  in  good 
number ;  but  in  the  stretches  that  are  comparatively  free  from 
ledges,  or  in  which  ledges  are  found  only  at  low  levels,  the  valley 
floor  may  be  broadly  opened,  and  but  few  of  the  many  flood 
plains  that  the  river  there  formed  at  various  levels  will  be  pre- 
served. These  open  basins,  often  bordered  by  a  single  high- 
scarped  terrace,  have  attracted  less  attention  than  they  deserve 


RIVER  TERRACES  IN  NEW  ENGLAND 


555 


in  the  discussion  of  terracing ;  and  well-developed  flights  of  ter- 
races have  been  given  an  importance  that  their  restricted 
occurrence  hardly  warrants. 

Distribution  of  High- Scarp  and  Low-Scarp  Terraces.  Ledges 
may  be  gradually  disclosed  at  various  points  up  and  down  the 
valley,  each  one  having  an  effect  in  cusp-making  and  terrace- 
keeping  appropriate  to  its  position  with  respect  to  the  valley  axis. 
The  frequent  swinging  of  the  meander  belt  from  side  to  side 
during  the  slow  degradation  of  the  valley  floor  requires  that  the 
discovery  of  every  ledge  lying  well  within  the  belt  of  wandering 
should  be  made  soon  after  the  stream  has  degraded  the  valley 
floor  to  the  level  of  the  ledge  top.  If  the  valley  floor  is  deepened 
ten  feet  during  a  complete  swing  of  the  meander  belt  to  and 
fro,  it  would  be  very  unlikely  that  a  ledge  within  the  breadth  of 
swinging  should  escape  discovery  until  the  valley  floor  was  worn 
down  twenty  feet  below  the  ledge  summit.  It  would  be  impos- 
sible for  the  discovery  to  be  postponed  so  long  that  the  stream 
should  first  encounter  the  ledge  fifty  feet  below  its  top,  unless 
the  ledge  were  situated  rather  far  to  one  side  of  the  valley  axis, 
where  it  might  not  be  encountered  by  the  down-sweeping  mean- 
ders every  time  the  meander  belt  swung  across  the  valley.  The 
more  likely  case  is  that  an  actively  swinging,  slowly  degrading 
stream  will  discover  the  upper  part  of  every  ledge  lying  well 
within  the  belt  of  wandering,  and  that  thereafter  the  stream  will 
frequently  swing  against  the  slope  of  the  ledge  at  lower  and 
lower  levels  as  the  valley  floor  is  deepened  ;  unless,  indeed,  an- 
other ledge,  nearer  the  axis  of  the  valley,  and  with  a  lower 
summit  than  the  ledge  already  discovered  in  its  neighorhood, 
prevents  the  river  from  swinging  laterally  so  far  as  it  had  at 
higher  levels. 

This  specialized  conception  of  the  terracing  process  leads  to 
some  reasonable  deductions  as  to  the  distribution  of  high-scarp 
and  low-scarp  terraces.  They  are  summarized  in  Fig.  79.  A  low- 
scarped  terrace  is  formed  near  the  western  border  of  the  belt  of 
wandering  shortly  after  degradation  has  begun  (see  further  side 
of  figure).  After  six  swings  the  river  discovers  a  ledge  (also  on 
the  further  side  of  the  diagram)  somewhat  within  the  belt  of 
wandering.  Then  all  the  terraces  of  earlier  swings  lying  back  of 


556 


PHYSIOGRAPHIC  ESSAYS 


this  ledge  will  be  preserved.  On  every  later  westward  swing  the 
river  is  halted  nearer  and  nearer  to  the  axis  of  the  valley.  Thus 
a  flight  of  stepping  terraces  is  formed  in  connection  with  a  series 
of  defended  cusps ;  but  on  account  of  the  absence  of  ledges  on 
the  near  side  of  the  diagram  and  of  the  increased  breadth  of 
wandering  as  the  later  stage  of  terracing  is  approached,  the  river 
destroys  all  traces  of  the  earlier  terraces  in  the  foreground,  where 
the  tenth  swing  produces  a  single  scarp  by  which  the  highest 
plain  descends  to  the  river  level.  Then  the  eleventh  and  twelfth 


FIG. 79 


swings  are  held  off  from  the  high  scarp  by  a  lower  ledge  on 
whose  slope  two  low-scarped  terraces  are  carved.  It  may  there- 
fore be  concluded  that  low,  undefended,  high-level  terraces  of 
early  swings  are  most  likely  to  be  preserved  back  of  defended 
cusps  of  later  swings ;  that  the  undefended  terraces  of  early 
swings  will  probably  be  swept  away  in  the  production  of  a  single 
high-scarped  terrace  wherever  broad  swinging  at  low  levels  is  not 
prevented  ;  and  that  when  high  scarps  occur  in  a  flight  of  step- 
ping terraces  they  are  more  likely  to  be  found  at  or  near  the  top 
than  near  the  bottom  of  the  flight. 

Effect  of  Rock  Barriers.    Superposition  upon  strong  rock  bar- 
riers has  already  been  considered  on  preceding  pages,  in  so  far 


RIVER  TERRACES  IN  NEW  ENGLAND 


557 


•&fa 


as  it  determines  the  separation  of  a  valley  into  several  compart- 
ments, in  each  of  which  the  flood  plain  is  thenceforward  graded 
with  respect  to  the  next  down-valley  barrier.  This  is  a  very 
familiar  condition  in  New  England,  as  the  water  power  in  the 
falls  or  rapids  on  the  down-valley  side  of  the  barriers  has  repeat- 
edly determined  the  location  of  our  manufacturing  villages  and 
cities.  In  the  present  section  brief  consideration  is  given  to  the 
effect  of  rock  barriers  in  producing  a  fixed  node,  as  Emerson  has 
called  it  (736),  in  a  stream  that  elsewhere  vibrates  freely  as  it 
meanders  and  swings  on  its  flood  plain.  It  is,  however,  not  yet 
clear  how  a  wandering  stream  will  behave  up  and  down  valley 
from  a  fixed 
node.  Several 
suppositions 
may  be  made. 

First,  the  me- 
anders will  sweep 
down  the  mean- 
der belt,  and  the 
meander  belt  will 
swing  to  and  fro 
across  the  valley, 

but  the  amplitude  of  both  movements  will  be  decreased  as  the 
node  is  approached,  and  extinguished  as  it  is  reached.  So  far  as 
my  observations  go,  this  condition  is  more  appropriate  down-valley 
than  up-valley  from  a  fixed  node.  Below  the  node  slight  curves 
may  be  formed  ;  these  may  develop  into  normal  meanders  (Fig. 
80 ;  the  river  flows  to  the  right),  as  they  sweep  away  from  the 
sill ;  but  such  development  will  probably  be  gradual,  and  hence 
the  valley  floor  will  widen  gradually  in  that  direction. 

Second,  the  meanders  may  continue  almost  in  full  force  as 
they  approach  the  node  from  up  the  valley,  merely  changing  in 
the  lowest  part  of  their  course  that  leads  directly  to  the  sill. 
This  might  involve  the  introduction  of  a  "  kink  "  into  the  mean- 
der system,  at  the  point  where  a  change  is-made  from  the  normal 
down-sweeping  curve  to  the  constrained  course  that  leads  to  the 
ledge.  That  such  a  sharp  bend  is  possible  seems  to  be  shown  by 
certain  peculiar  forms  in  the  meanders  of  the  Theiss  on  the  plain 


FIG.  80 


558  PHYSIOGRAPHIC  ESSAYS 

of  Hungary,  it  being  probable  that  bends  of  this  kind  result  from 
the  faster  down-sweeping  of  some  meanders  than  of  others.  The 
considerable  breadth  of  flood  plain  often  observed  next  upstream 
from  a  node  supports  this  supposition. 

Third,  the  fixed  node  may  perhaps  induce  the  formation  of 
free  nodes,  evenly  spaced  from  the  ledge  of  superposition ;  then 
between  the  fixed  node  and  the  free  nodes,  the  stream  might 
vibrate  as  a  stretched  string  vibrates  when  it  is  lightly  "  stopped  " 
at  a  third  or  a  quarter  of  its  length.  Symmetrical  free  terrace 
cusps  would  result  from  this  process.  So  systematic  a  movement 
would  seem  to  be  possible  only  in  rare  cases,  if  at  all ;  but  the 
terraces  of  Chicopee  river  above  Beecham  Falls,  a  few  miles 
northeast  of  Springfield,  Massachusetts,  give  some  support  to 
this  possibility.  Further  observation  is  needed  in  this  direction. 

When  two  barriers  occur  near  together,  leaving  a  free  space 
of  half  a  mile  or  so  between  them,  the  river  is  fixed  at  two  nodes, 
but  may  vibrate  between  them.  A  remarkable  case  of  this  kind 
is  found  in  the  valley  of  Saxtons  river  at  Bellows  Falls,  Vermont, 
as  described  on  a  subsequent  page. 

Relation  of  Terrace  Patterns  on  the  Two  Sides  of  a  Valley. 
It  has  been  already  pointed  out  as  a  matter  generally  accepted 
by  many  observers  that  the  terraces  on  the  two  sides  of  a  valley 
need  not  necessarily  agree  in  number  or  in  height.  The  relations 
of  terrace  patterns  as  seen  in  plan  on  the  two  sides  of  a  valley 
have  been  less  considered.  It  is  desired  here  to  indicate  certain 
relations  that  seem  to  obtain  in  special  cases. 

When  a  group  of  defended  cusps  occurs  in  a  valley  of  moder- 
ate breadth,  the  stream,  must  have  been  repeatedly  deflected 
across  the  valley  by  the  defending  ledges,  so  as  often  to  impinge 
upon  the  opposite  side  of  the  valley  in  about  the  same  place. 
Hence  reentrants  of  more  than  usual  size  may  there  be  worn  out, 
next  up-valley  from  which  a  group  of  free  cusps  may  thus  come 
to  stand  about  opposite  the  defended  cusps.  If  the  meander  next 
above  the  ledge  is  somewhat  compressed,  the  stream  may  strike 
more  squarely  across  the  valley  and  under-cut  the  down-valley  side 
of  a  terrace  with  somewhat  greater  vigor  than  usual.  The  valley 
of  the  Westfield  river,  a  mile  or  so  upstream  from  Westfield, 
Massachusetts,  offers  some  remarkable  examples  of  this  kind. 


RIVER  TERRACES  IN  NEW  ENGLAND  559 

When  a  side  stream  enters  the  valley  of  a  degrading  main 
stream,  it  tends  to  push  the  main  stream  away,  and  thus  causes 
it  to  wear  out  reentrants  opposite  to  the  entrance  of  the  side 
stream.  Reacting  from  such  reentrants,  the  main  stream  will 
strike  across  the  valley  and  scour  out  another  group  of  reentrants 
below  the  mouth  of  the  side  stream.  When  this  transverse  de- 
flection of  the  main  stream  is  confirmed  by  the  occurrence  of  a 
guiding  ledge,  the  reentrants  will  be  all  the  more  persistently 
and  repeatedly  carved  out.  The  Connecticut  seems  to  show  an 
example  of  double  control  by  the  Westfield  and  by  ledges  in  the 
southern  part  of  Springfield,  Massachusetts  ;  and  the  Westfield 
itself,  two  miles  east  of  Westfield  village,  offers  a  similar  example 
of  double  control. 

Ratio  of  Sweeping,  Swinging,  and  Degrading.  The  foregoing 
analyses  of  the  process  by  which  a  graded  and  wandering  river 
may  degrade  and  terrace  its  valley  suggests  a  method  by  which 
a  quantitative  determination  may  be  made  of  the  ratios  of  sweep- 
ing, swinging,  and  degrading.  If  numerous  measures  are  taken 
of  the  difference  of  level  between  adjacent  terraces  in  a  certain 
section  of  a  valley,  it  may  be  expected  that  two  groups  of  mini- 
mum differences  should  be  found  ;  the  group  of  smaller  values 
representing  the  deepening  of  the  valley  floor  in  the  interval 
between  the  down-valley  sweeping  of  two  successive  meanders ; 
the  group  of  larger  values  representing  the  deepening  between 
two  successive  swings  of  the  meander  belt. 

If  measures  of  this  kind  were  taken  in  different  sections  of  a 
valley  system,  it  might  be  possible  to  determine  from  their  vari- 
ations whether  an  even  regional  uplift  or  a  tilting  were  chiefly 
responsible  for  the  activity  of  the  river  in  carving  its  terraces,  as 
the  following  considerations  will  show. 

In  the  case  of  uniform  uplift  over  a  large  area  let  it  be  assumed 
that  the  movement  was  rather  quickly  initiated,  and  then  steadily 
continued  until  it  rather  rapidly  weakened  at  its  close.  We  should 
then  expect  that  the  terrace  scarp  marking  the  interval  between 
two  lateral  swings  of  the  meander  belt  would  be  of  greatest 
measure  and  relatively  constant  in  the  lower  course  of  the  main 
river ;  but  the  slow  initiation  of  the  uplift  might  possibly  be  re- 
corded by  a  few  low  terraces  at  the  top  of  the  series  ;  the  slow 


560  PHYSIOGRAPHIC  ESSAYS 

close  of  the  uplift  and  the  very  slow  degradation  of  the  valley 
floor  in  later  time  might  be  recorded  by  a  few  terraces  of  lower 
and  lower  scarps  at  the  base  of  the  series.  If  any  terrace  in  the 
lower  course  of  the  river  could  be  followed  up  the  valley,  it  would 
assume  a  relatively  higher  and  higher  position  in  the  series ;  for 
when  the  river  had,  in  its  lower  course,  worn  down  its  valley  floor 
to  a  low  grade  at  the  close  of  the  period  of  uplift,  there  would 
still  be  a  considerable  amount  'of  degradation  permitted  to  the 
middle  and  upper  part  of  the  river.  As  a  result,  the  very  low 
terraces  at  the  base  of  the  series  near  the  river  mouth  might 
gain  a  higher  rank  and  a  greater  scarp  height  farther  upstream. 
If  the  terraces  could  be  followed  up  to  the  headwaters  of  the 
river  system,  they  would  become  narrower  and  finally  disappear 
in  single-scarped  V-shaped  valleys.  So  far  as  they  could  be  rec- 
ognized, the  upper  members  of  a  headwater  series  might  corre- 
spond in  date  to  the  basal  members  near  the  river  mouth  ;  while 
the  basal  members  of  a  headwater  series  would  decrease  in  scarp 
height  as  they  were  traced  down-valley,  until  they  at  last  merged 
in  the  even  flood  plain  of  the  middle  or  lower  river  course.  So 
many  are  the  irregularities  of  drift  terraces  that  there  has  not  to 
my  knowledge  been  any  systematic  attempt  to  discover  the  facts 
by  which  these  deductions  might  be  confirmed. 

In  the  case  of  a  tilting,  with  fulcrum  at  the  river  mouth  and 
at  right  angles  to  the  general  river  course,  the  maximum  height 
of  two-swing  terrace  scarps  would  be  found  somewhere  near  the 
middle  course  of  the  river,  and  the  scarp  height  would  thence 
decrease  down-valley  and  up-valley.  It  seems  that  in  such  a  ter- 
race system  as  that  of  the  Connecticut  it  may  be  possible  to 
apply  this  test  and  thus  gain  from  the  dimensions  of  the  terraces 
a  direct  proof  as  to  the  kind  of  movement  by  which  the  work  of 
terracing  was  initiated,  as  well  as  a  confirmation  of  the  evidence 
already  in  hand  regarding  the  nature  of  post-glacial  movement 
in  the  New  England  province. 

Relation  of  the  Preceding  Deductions  to  the  Observations  de- 
scribed in  the  Following  Sections.  The  facts  presented  in  the 
following  sections  are  chiefly  details  of  structure  and  form, 
directly  observable ;  changes  of  form  are  occasionally  noted, 
but  these  are  of  relatively  small  measure.  All  these  details  are 


RIVER  TERRACES  IN  NEW  ENGLAND  561 

but  the  present  members  of  a  long  series  of  facts,  every  one  of 
which  might  have  been  recorded,  had  observers  been  living  to 
witness  them  ;  and  then  the  origin  of  terraces  would  be  fully 
understood.  But  the  earlier  members  of  the  series  are  hopelessly 
lost  to  observation  from  being  prehistoric.  In  their  unavoidable 
absence  theory  attempts  to  supply  a  series  of  conditions,  pictured 
by  the  reasonably  guided  imagination,  which  shall  imitate  the 
series  of  past  facts,  and  thus,  as  it  were,  call  them  to  life,  bring 
them  into  the  field  of  vision.  The  success  of  the  theory  is  not 
to  be  measured  so  much  by  the  apparent  reasonableness  of  its 
fundamental  suppositions,  or  by  the  definiteness  with  which  vari- 
ous imaginary  consequences  may  be  deduced  from  it,  as  by  the 
accuracy  with  which  the  observable  members  of  the  deduced  con- 
sequences imitate  the  facts  of  actual,  occurrence.  The  greater 
the  number  of  peculiar  categories  of  observed  facts,  the  greater 
the  probable  correctness  of  a  theory  whose  deduced  consequences 
can  match  all  of  them.  Hence  the  importance  of  minute  obser- 
vation and  careful  generalization  on  the  one  hand,  and  of  accurate 
and  detailed  deduction  on  the  other.  Hence  also  the  importance 
of  carefully  distinguishing  these  unlike  processes  in  order  that 
their  results  may  be  systematically  confronted  in  an  unprejudiced 
comparison.  The  elaboration  of  the  deductions  in  the  preceding 
sections  therefore  seems  to  be  as  necessary  a  part  of  the  study 
of  terraces  as  is  the  accumulation  of  observations  for  presentation 
in  the  following  sections. 

The  theory  of  terracing  has  here  been  presented  before  the 
observations  of  terraces  are  detailed,  because  it  is  the  theory  with 
its  deduced  consequences  and  not  the  facts  that  are  on  trial.  Fur- 
thermore, it  is  only  after  the  presentation  of  the  theory  that  the 
pertinent  facts  can  be  conveniently  selected  from  among  many 
others  and  that  their  bearing  can  be  clearly  appreciated.  True, 
the  attempt  might  be  made  independent  of  any  theory  to  observe 
all  facts  thoroughly  and  to  record  them  minutely,  in  the  hope  of 
including  every  item  that  could  be  asked  for  in  the  testing  of 
whatever  theory  should  afterwards  be  invented ;  but  under  this 
method  of  work  items  of  minor  importance  are  confused  with 
those  of  major  importance,  and  their  recital  becomes  so  long 
that  the  beginning  is  forgotten  before  the  end  is  reached.  As  a 


562  PHYSIOGRAPHIC  ESSAYS 

matter  of  fact,  observational  study  of  this  kind  is  notoriously 
incomplete.  Indeed,  the  terrace  problem,  like  many  others,  gives 
striking  illustration  of  the  difficulty,  if  not  the  impossibility,  of 
really  seeing  all  the  essential  facts  when  only  the  eyes  of  the 
observer  are  trusted ;  and  it  illustrates  at  the  same  time  the 
critical  power  that  is  given  to  observation  when  it  is  directed 
towards  significant  points  instead  of  being  allowed  to  wander  in 
the  vain  hope  of  finding  all  the  facts  before  theorizing  is  begun. 
For  example,  if  it  is  not  already  manifest  from  the  deductions 
of  the  preceding  paragraphs  that  the  terrace  spurs  formed  of 
grouped  cusps  and  the  outcropping  ledges  that  are  associated 
with  them  are  of  particular  significance,  no  doubt  will  remain  on 
this  point  when  the  observations  detailed  in  the  following  para- 
graphs are  reviewed ;  yet  in  all  that  has  thus  far  been  written  on 
this  subject  in  New  England,  no  description  of  grouped  cusps  is 
to  be  found,  and  no  recognition  of  the  significance  and  the  gen- 
erality of  the  relation  between  ledges  and  cusps  is  recorded.  It 
is  as  if  it  had  been  thought  that  all  parts  of  a  terrace  are  equally 
significant ;  that  when  ledges  appear  at  the  terrace  base  they  are 
of  no  particular  importance.  Even  the  citations  made  above  from 
the  writings  of  Edward  Hitchcock  do  not  show  that  that  careful 
observer  thought  the  ledges  he  described  were  of  any  more  than 
local  importance ;  and  certainly  no  later  observer  has  been  led 
by  Hitchcock's  essay  to  understand  the  control  that  ledges  exer- 
cise in  determining  terrace  pattern  and  terrace  preservation. 
Yet  after  apprehending  this  control  and  discovering  the  sugges- 
tive relation  that  must  obtain  between  ledges  and  cusps,  the  ob- 
server no  longer  strays  over  his  field ;  he  directs  his  steps  and 
secures  in  the  least  possible  time  the  greatest  possible  results. 

Largely  deductive  as  the  preceding  portion  of  this  essay  is  in 
its  present  form,  the  reader  should  not  suppose  that  it  was  pre- 
pared independently  of  observation.  The  actual  progress  through 
the  problem  has  involved  repeated  alternations  of  external  and 
internal  work ;  the  collection  of  observations  and  the  induction 
of  generalizations  on  the  one  hand,  and  on  the  other  hand  the 
invention  of  hypotheses,  the  deduction  of  their  consequences, 
the  confrontation  of  deductions  with  generalizations,  the  evalua- 
ation  of  agreements,  and  the  repeated  revision  of  the  whole 


RIVER  TERRACES  IN  NEW  ENGLAND  563 

process.  It  is  not  profitable  to  expose  the  personal  history  of  a 
study  all  through  these  stages,  for  the  convenience  of  the  reader 
is  best  served  by  a  careful  separation  of  its  two  phases  ;  and  to 
the  second  of  these  we  may  now  turn  in  Part  IV  with  no  more 
delay  than  is  required  for  the  citation  of  the  following  pertinent 
extract  from  Play  fair's  "  Illustrations  of  the  Huttonian  Theory 
of  the  Earth."  After  pointing  out  that  to  wait  for  the  comple- 
tion of  discoveries  in  other  sciences  before  theorizing  in  geology 
"would  not  be  caution,  but  timidity,  and  an  excess  of  prudence 
fatal  to  all  philosophical  inquiry,"  this  lucid  writer  of  a  century 
ago  proceeds  as  follows  : 

The  truth,  indeed,  is,  that  in  physical  inquiries  the  work  of  theory  and 
observation  must  go  hand  in  hand,  and  ought  to  be  carried  on  at  the  same 
time,  more  especially  if  the  matter  is  very  complicated,  for  there  the  clue 
of  theory  is  necessary  to  direct  the  observer.  Though  a  man  may  begin  to 
observe  without  any  hypothesis,  he  cannot  continue  long  without  seeing 
some  general  conclusion  arise  ;  and  to  this  nascent  theory  it  is  his  business 
to  attend,  because,  by  seeking  either  to  verify  or  to  disprove  it,  he  is  led  to 
new  experiments  or  new  observations.  He  is  also  led  to  the  very  experi- 
ments and  observations  that  are  of  the  greatest  importance,  namely,  to  those 
instantiae  cruets,  which  are  the  criteria  that  naturally  present  themselves  for 
the  trial  of  every  hypothesis.  He  is  conducted  to  the  places  where  the 
transitions  of  nature  are  most  perceptible,  and  where  the  absence  of  former, 
or  the  presence  of  new  circumstances,  excludes  the  action  of  imaginary 
causes.  By  this  correction  of  his  first  opinion,  a  new  approximation  is  made 
to  the  truth  ;  and  by  the  repetition  of  the  same  process,  certainty  is  finally 
obtained.  Thus  theory  and  observation  mutually  assist  one  another ;  and 
the  spirit  of  system,  against  which  there  are  so  many  and  such  just  com- 
plaints, appears,  nevertheless,  as  the  animating  principle  of  inductive 
investigation.  The  business  of  sound  philosophy  is  not  to  extinguish  this 
spirit,  but  to  restrain  and  direct  its  efforts"  (524,  525). 

IV.  OBSERVATIONS  OF  RIVER  TERRACES  IN  NEW  ENGLAND 

Valley  of  the  We s (field  River,  Massachusetts  :  Eastern  Section. 
This  branch  of  the  Connecticut  rises  among  the  hard-rock  Berk- 
shire hills  of  western  Massachusetts,  the  round  remnants  of  the 
uplifted  and  dissected  Cfetaceous  peneplain  of  the  Appalachian 
province,  and  thence  flows  eastward  part  way  across  the  broad 
valley  lowland  that  has  been  excavated  in  the  weaker  Triassic 
formation  during  later  Tertiary  time.  Between  the  eastern  base 


564  PHYSIOGRAPHIC  ESSAYS. 

of  the  crystalline  uplands  and  the  ridge  formed  on  the  main 
sheet  of  extrusive  trap  within  the  Triassic  area,  the  stream  has 
excavated  a  fine  series  of  terraces  in  the  unconsolidated  drift 
deposits  that  have  been  so  abundantly  spread  over  the  Triassic 
lowland  by  the  Connecticut  and  its  tributaries. 

The  village  of  Westfield  lies  near  the  middle  of  this  terrace 
system  and  serves  to  mark  the  separation  of  its  unlike  eastern  and 
western  divisions.  In  the  eastern  division,  Westfield  river,  rein- 
forced by  Little  river,  a  branch  which  leaves  the  hills  two  miles 
south  of  the  main  stream,  has  opened  a  broad  basin  at  an  eleva- 
tion of  about  140  feet.  The  basin  floor  is  nearly  everywhere 
inclosed  by  the  strong  scarp  of  a  single  high  terrace  whose 
plain  stands  at  altitudes  of  240  to  280  feet.  The  plain  is  not 
of  simple  origin.  On  the  southeast  its  surface  is  rolling,  as  if 
consisting  of  morainic  and  kame-like  deposits.  On  the  north  it 
is  smooth  and  its  sands  are  fine  enough  to  have  been  raised  in 
occasional  dunes  ;  here  the  plain  falls  off  southwestward  to  the 
valley  of  Powdermill  brook  in  a  series  of  lobes,  whose  inter- 
mediate depressions  are  too  large  to  have  been  excavated  by 
local  drainage  :  hence  it  is  probable  that  this  part  of  the  plain 
is  a  delta  front  in  one  of  the  areas  of  deposition  described  by 
Emerson  (650-653).  South  of  the  main  basin  the  smoother 
part  of  the  high  plain  (Poverty  plains)  is  regarded  by  Diller 
(265)  as  an  extension  of  the  plain  on  the  north,  the  originally 
continuous  surface  having  been  formed  by  the  flooded  Con- 
necticut. Westward  up  the  Westfield  valley  the  high  plain 
ascends  towards  the  hills  and  is  of  much  coarser  materials 
than  elsewhere ;  this  part  seems  to  have  been  capped  by  the 
local  outwash  from  the  high  ground  during  the  period  of  aggra- 
dation. As  the  coarse  upper  gravels  lie  on  fine  sands  and  silts, 
this  high  plain  is  probably,  like  the  one  on  the  north,  a  delta 
surface,  built  up  in  standing  water. 

The  strong  scarps  B  (Fig.  82),  by  which  the  high  drift 
plains  descend  to  the  main  low-level  basin,  everywhere  present 
concave  reentrants,  whose  curves  unite  in  cusps  —  usually  two- 
sweep  cusps  —  of  greater  or  less  acuteness ;  and  this  shows 
that  the  streams  have  repeatedly  swung  against  the  terrace 
scarp,  under-cutting  it  and  pushing  it  back,  after  the  present 


RIVER  TERRACES  IN  NEW  ENGLAND  565 

grade  had  been  essentially  reached.  The  curved  reentrants 
are  of  somewhat  larger  radius  on  the  north  than  on  the  south, 
as  if  they  had  been  scoured  by  the  Westfield  and  Little  rivers, 
respectively.  With  the  significant  exception  of  certain  points 
on  the  east  and  west,  to  be  described  below,  all  these  cusps,  at 
least  twenty-four  in  number,  are  free,  undefended  by  ledges. 
We  have,  therefore,  here  an  example  of  a  vigorous  stream  with 
a  good-sized  branch  working  in  a  broad  deposit  of  loose  drift, 
and  free  to  sweep,  swing,  and  wander  over  a  large  area.  A  late 
stage  of  terracing  has  been  reached,  for  the  wide  plain  is  nearly 
or  quite  reduced  to  grade  with  respect  to  a  relatively  perma- 
nent local  base-level  in  the  trap-ridge  notch  on  the  east.  The 
detention  of  further  degradation  by  the  trap  barrier  is  a  factor 
of  importance  ;  for  many  recent  swings  of  the  streams  must 
have,  on  this  account,  tended  to  destroy  earlier  terraces  by 
reducing  them  all  to  one  level,  instead  of  tending  to  make  new 
ones  at  lower  levels.  Whatever  flood  plains  may  have  been  pro- 
duced during  the  excavation  of  the  present  basin  floor,  the 
streams  have  now  so  well  taken  advantage  of  their  opportunity 
for  lateral  corrasion  or  "  sapping "  that  terraces  at  high  and 
intermediate  levels  are  nearly  everywhere  obliterated,  and  even 
the  low  terraces  are  as  a  rule  destroyed  by  the  broad  swinging 
of  the  streams  at  their  present  grade. 

Westfield  river  is  at  present  nowhere  working  against  the 
base  of  the  high  terrace  on  the  north ;  its  actual  course  lies 
about  half  a  mile  to  the  south  of  the  scarp,  but  several  of  its 
former  courses  along  the  terrace  base  are  clearly  revealed  in  a 
series  of  shallow,  swampy  troughs,  the  remains  of  channels  from 
which  escape  seems  to  have  been  effected  by  repeated  short- 
cuts or  cut-offs.  The  river  is  now  engaged  at  several  points  in 
grading  down  to  modern  flood-plain  level  a  broad  and  low  ter- 
race, parts  of  which  are  not  yet  destroyed. 

Little  river  was,  in  1901,  sweeping  against  its  high  terrace  on 
the  south  at  two  points  a  little  east  of  the  New  Haven  and 
Northampton  Railroad.  Here  the  usual  cover  of  vegetation  has 
been  removed  from  the  scarp,  the  sands  are  under-cut,  and  the 
face  of  the  scarp  is  sliding  intermittently  into  the  stream.  Small 
sand  dunes  are  formed  at  the  top  of  the  sliding  bank  by  the 


566  PHYSIOGRAPHIC  ESSAYS 

northwest  winds  which  sweep  the  sand  up  from  below.  It  is 
evident  that,  by  a  repetition  of  sweeping  and  swinging  of  this 
kind,  the  high  terrace  has  been  worn  back  to  its  present 
outline. 

Where  the  rivers  have  withdrawn  from  the  high-scarped 
terrace,  flat  fans  have  been  formed  at  the  outlet  of  the  minor 
lateral  valleys  of  small  brooks,  or  beneath  little  gullies  of  wet- 
weather  wash.  The  fan  of  Powdermill  brook,  for  example, 
forms  a  low  barrier,  X  (Fig.  82),  across  a  deserted  channel 
of  Westfield  river,  and  thus  determines  a  swampy  depression 
just  northeast  of  Westfield  station.  The  further  course  of  the 
brook  follows  the  marshy  deserted  channels  of  Westfield  river 
at  the  base  of  the  scarp  for  over  a  mile. 

It  would  be  difficult  to  find  better  illustrations  of  the  deduc- 
tions presented  on  page  545  than  are  offered  by  this  beautiful 
basin.  The  two  chief  streams,  far  from  exhibiting  any  inca- 
pacity to  open  their  valley  floors,  have  now  widened  them  to  a 
greater  breadth  than  ever  before.  Whatever  decrease  of  capacity 
may  be  due  to  decrease  of  stream  volume  and  of  stream  slope, 
and  whatever  increase  of  work  may  be  due  to  the  more  active 
wash  of  side  streams  on  account  of  gain  in  height  of  valley 
sides,  the  main  streams  are  certainly  more  competent  to  cor- 
rade  laterally  now  than  they  have  ever  been,  and  there  is  every 
probability  that  they  will  in  the  future  continue  to  widen  their 
basin  still  further  by  intermittent  attacks  on  its  border  until 
restrained  by  defending  ledges  or  by  the  hand  of  man.  Indeed, 
so  nearly  complete  is  the  obliteration  of  all  terraces  above  the 
level  of  the  present  basin  floor,  one  might  be  tempted  to  con- 
clude that  the  Westfield  and  Little  rivers  never  produced  any 
extended  series  of  flood  plains  in  this  division  of  their  course 
at  higher  levels  than  those  of  modern  times,  until  an  examina- 
tion of  the  western  division  of  the  Westfield  terraces  proves 
that  flood  plains  must  have  been  produced  at  various  levels  in 
the  eastern  division  as  well  as  elsewhere 

Evidently  then,  as  far  as  this  example  goes,  it  affords  no 
evidence  that  the  production  and  preservation  of  terraces  is 
due  to  any  incompetence  arising  from  decrease  in  the  vol- 
ume or  from  other  changes  in  the  habits  of  our  New  England 


RIVER  TERRACES  IN  NEW  ENGLAND 


567 


streams.  Terrace  preservation  must  be  due  to  some  control 
external  to  the  streams  ;  and  of  this  we  find  immediate  proof 
on  looking  at  the  eastern  and  western  inclosure  of  the  broad 
basin  just  described. 

The  basin  is  inclosed  on  the  east  by  the  approach  of  a  de- 
fended spur,  A  (Fig.  81),  on  the  north  towards  a  free  spur,  B, 
on  the  south,  beyond  which  a  subordinate  basin,  C,  is  again 
opened.  The  defended  spur  carries  a  terrace  plain  at  a  height 
of  two  hundred  feet,  and  the  highest  plain  rises  farther  north  by 


FIG.  81 

"a  faded  scarp  of  gentle  slope.  Sandstone  ledges  are  abundant 
along  the  western  base  of  the  spur ;  they  are  unusually  steep,  in 
part  because  of  the  eastward  dip  of  the  strata,  and  in  part  be- 
cause of  a  certain  amount  of  under-cutting  by  the  Westfield 
when  it  ran  beneath  them.  The  eastern  side  of  the  spur  is  not 
trimmed  close  to  the  defending  ledges,  but  illustrates  the  un- 
symmetrical  relations  shown  in  Fig.  74.  Widely  as  the  river 
has  swung  from  side  to  side  in  the  basin  farther  west,  it  was 
here  strongly  constrained.  Not  only  so ;  Westfield  river  has 
been  somewhat  impelled  northward  by  the  entrance  of  Little 


568  PHYSIOGRAPHIC  ESSAYS 

river  from  the  south  (west  of  the  area  shown  in  Fig.  81)  ;  and 
it  is  probably  in  part  at  least  on  this  account  that  the  basin 
has  been  so  well  broadened  northward ;  yet  on  every  sweep  or 
swing  against  the  sandstone  reef  the  river  was  not  only  restrained 
from  further  northward  conquest  at  that  point,  but  was  deflected 
obliquely  southward  across  the  valley.  It  is  very  probable  that 
the  excavation  of  the  subordinate  basin  C  is  due  to  this  cause, 
for  it  is  opened  farther  to  the  south  than  to  the  north.  Three 
strong  southward  loops  of  the  river,  Z>,  E,  F  (including  the 
present  one),  are  here  recorded,  and  it  can  hardly  be  by  chance 
that  the  river  has  thus  repeatedly  turned  southward  on  its  way 
to  the  fixed  node  G  in  the  trap-ridge  notch. 

Nearly  opposite  to  this  well-defended  spur,  but  a  little  farther 
westward,  the  free  spur  B,  rising  to  the  full  height  of  the  drift 
plain,  separates  the  subordinate  eastern  basin  C,  and  that  part 
of  the  main  basin  H  which  has  been  scoured  out  chiefly  by 
Little  river.  Unlike  the  defended  spur  on  the  north,  the  free 
spur  is  not  a  relatively  permanent  feature  of  the  valley ;  it  will 
be  removed  without  difficulty  if  Little  river  takes  a  fancy  to 
trim  away  its  western  base.  Nevertheless,  its  occurrence  to-day 
does  not  appear  to  be  altogether  a  matter  of  chance,  for  it  seems 
to  illustrate  the  systematic  features  described  on  page  558. 

The  main  basin  is  inclosed  on  the  northwest  by  a  well- 
defended  spur,  known  as  Prospect  Hill,  A,  (Fig.  82),  just  west 
of  Westfield  station;  this  will  be  further  described  with  the 
terraces  of  the  western  division  of  the  valley.  On  the  southeast 
Little  river  is  held  from  swinging  at  present  levels  by  superpo- 
sition on  a  transverse  sandstone  ledge,  to  which  brief  reference 
will  be  made  farther  on.  The  contrast  between  the  openness' 
of  the  main  basin,  excavated  where  the  streams  have  not  been 
restrained  by  ledges,  and  the  narrowness  of  the  entering  valleys 
where  ledges  have  been  encountered,  is  most  striking. 

Western  Section.  The  western  division  of  the  Westfield 
terraces,  occupying  the  valley  for  about  four  miles  from  West- 
field  village  to  the  base  of  the  hills,  is  of  greater  interest  than 
the  eastern,  inasmuch  as  it  preserves  the  records  of  river  work 
at  many  levels  between  the  highest  and  the  lowest  plains.  I 
have  prepared  a  somewhat  detailed  account  of  it  for  publication 


RIVER  TERRACES  IN   NEW  ENGLAND 


569 


in  the  American  Journal  of  Science,  and  hence  shall  here  refer  only 
to  such  features  as  confirm  the  deductions  of  earlier  paragraphs. 
The  chief  features  of  this  interesting  locality  are  shown  in  a 
bird's-eye  view  in  Fig.  82,  as  if  looking  northeast  from  a  height 
of  several  thousand  feet  above  the  left  front  corner  of  the 
diagram.  The  Boston  and  Albany  Railroad  runs  through  the 


PHYSIOGRAPHIC  ESSAYS 

view  for  a  distance  of  about  a  mile  and  a  half ;  the  foreground 
scale  is  larger  than  that  for  the  background ;  heights  are 
exaggerated  ;  outcropping  ledges  are  black. 

From  Westfield  to  a  small  rural  settlement  known  as 
Pochassic  Street,  two  miles  to  the  west,  many  small  ledges 
are  exposed,  and  many  stepping  terraces  occur  along  the 
northern  side  of -the  valley.  Few  ledges  are  seen  on  the 
southern  side,  and  there  the  valley  is  generally  bordered  by 
a  strong  upper  terrace  with  a  few  low  terraces  beneath  it. 
On  the  northern  side  there  are  four  groups  of  defended  ter- 
race cusps,  forming  what  may  be  called  the  Pochassic  (just 
to  the  left  of  Fig.  82),  Perry's  (K),  Brown's  (F),  and  Prospect 
spurs  (A),  while  curved  reentrants  have  been  excavated  between 
the  spurs  where  ledges  are  rare  or  wanting.  The  reentrants 
show  that  the  river  has  everywhere  attempted  to  widen  its 
valley,  while  the  terraces  on  the  defended  spurs  show  that  the 
widening  has  been  locally  prevented  by  the  outcropping  ledges. 
Wherever  free  cusps  occur  they  exhibit  the  patterns  deduced 
as  of  common  occurrence  on  page  543.  None  of  the  .combinations 
there  deduced  as  rare  are  found.  The  cusps  are  usually  more 
closely  trimmed  on  the  up-valley  than  on  the  down-valley  side. 
It  would  be  difficult  to  imagine  a  more  complete  confirmation 
of  Miller's  theory  than  is  here  presented. 

Special  mention  may  be  made  of  a  few  features.  Just  east  of 
Pochassic  Street  a  series  of  at  least  nine  terraces,  H  to  My  may 
be  counted.  They  range  in  height  from  eight  to  fifteen  feet, 
and  thus  suggest  a  rough  measure  for  the  amount  of  valley 
deepening  during  a  swing  of  the  river  southward  across  the 
valley  and  back  again.  This  maximum  number  is  evidently 
dependent  on  the  numerous  ledges  here  discovered  at  all  levels 
from  highest  to  lowest.  Although  no  other  part  of  the  valley 
shows  so  many  terraces,  it  must  be  concluded  that  flood  plains, 
continuous  with  the  remnants  here  preserved,  were  made  far  up 
and  down  the  valley ;  and  hence  that  the  river  was  essentially 
at  grade  during  the  whole  process  of  valley  degradation.  Two 
terraces  at  the  top  of  this  flight,  in  the  reentrant  east  of 
Pochassic  Street,  exhibit  minor  reentrants  of  small  radius  and 
large  arc  near  H  and  Jf\  comparable  to  the  curves  of  the 


RIVER  TERRACES  IN  NEW  ENGLAND  571 

present  river,  thus  indicating  that  no  significant  change  of  volume 
has  occurred  since  the  work  of  terracing  began.  A  broad  ter- 
race plain  stretches  back  of  Perry's  spur,  K,  and  four  low 
terraces  rise  above  it  to  higher  levels,  showing  that  four  north- 
ward swings  were  here  executed.  The  fifth  terrace  (counting 
from  the  top  of  the  series)  runs  forward  to  Perry's  spur,  be- 
cause the  highest  ledge  of  that  spur  was  discovered  when  the 
river  was  making  its  fifth  northward  swing.  It  is  worth  noting 
that  several  defending  ledges  in  this  spur  would  be  unseen  but 
for  road  and  railroad  cuts.  The  fourth  terrace  swings  forward 
in  a  long  sweeping  curve  to  the  apex  of  Brown's  spur,  Fy  because 
the  summit  ledge  was  there  found  by  the  fourth  northward 
swing.  Only  two  distinct  terraces  occur  on  the  high  plain  back 
of  Prospect  spur,  A,  because  the  ledges  in  that  spur  rise  still 
higher  than  in  Brown's  spur.  In  a  word,  the  river  has  always 
shown  a  capacity  for  broad  swinging  until  it  became  hampered 
in  its  movements  by  coming  upon  previously  buried  spurs. 
Brown's  spur  is  peculiar  in  being  closely  trimmed  on  the  down- 
valley  side  as  well  as  on  the  up-valley  side.  Prospect  spur  has 
a  terraced  reentrant,  C,  scoured  out  at  mid-height  with  small 
radius  and  large  arc,  far  back  on  its  .up-valley  side ;  that  is,  a 
meander  of  the  river  has  there  been  twice  compressed  against 
defending  ledges,  after  the  style  of  Fig.  73.  Elsewhere  the 
meanders  seem  to  have  slipped  past  the  defending  ledges,  after 
the  style  of  Figs.  68-71. 

The  terraces  on  the  south  side  of  the  valley  are  in  several 
cases  determined  indirectly  by  the  ledges  on  the  north  side. 
This  is  most  distinctly  the  case  where  the  river  formerly  swept 
forward  from  the  lowest  and  farthest  forward  of  the  Pochassic 
ledges  M,  and  consequently  cut  out  one  of  the  deepest  reentrants 
on  the  south  side  of  the  valley  P.  A  single  scarp  now  descends 
from  the  high-level  plain  into  this  strong  recess.  Similar  but 
less  manifest  relations  are  suspected  elsewhere  ;  thus  K] K" K"' 
on  the  north  may  correspond  with  S* ,  S",  S"r  on  the  south. 
Conversely,  a  number  of  low-level  terraces  remain  on  the  south 
side  of  the  valley  south  of  Brown's  spur,  perhaps  because  the 
repeated  northward  swings  of  the  river  into  the  largest  north- 
ward reentrant,  that  between  Brown's  and  Prospect  spurs,  have 


572  PHYSIOGRAPHIC  ESSAYS 

not  required  their  removal.  The  numerous  free  cusps  here 
found  exhibit  the  features  already  deduced  as  of  common  occur- 
rence. It  is  intended  to  make  a  close  measurement  of  the 
slopes  of  these  terrace  plains  in  the  hope  of  correlating  the 
now  separate  remnants  of  single  flood  plains,  and  thus  tracing 
the  history  of  the  terracing  process  in  some  detail. 

Little  River.  A  few  words  may  be  said  about  Little  river, 
although  the  southern  side  of  its  valley  has  not  been  closely 
studied.  The  valley  of  this  stream  is  divided  into  three  sections 
by  two  barriers  of  sandstone,  next  upstream  from  which  are 
considerable  bodies  of  till.  The  till  has  been  cut  down  to  grade 
with  the  sandstone  barriers,  but  the  valley  in  the  till  is  held  to 
a  small  width,  practically  without  terraces.  Relatively  few  ter- 
races are  found  even  where  the  valley  is  bordered  by  stratified 
drift.  In  explanation  of  this  it  should  be  noted  that  Little  river 
is  smaller  than  the  Westfield,  and  that  a  small  stream  must  be 
hurried  in  attempting  to  keep  pace  with  the  degrading  action  of 
its  master.  Hence  the  smaller  stream  will  have  little  oppor- 
tunity for  lateral  swinging  and  terracing  so  long  as  it  runs 
through  loose  drift  to  a  more  actively  degrading  master  stream. 
There  are  two  conditions  under  which  opportunity  for  lateral 
swinging  will  be  presented  to  the  smaller  stream.  First,  when 
the  master  stream  has  effectively  ceased  degrading  its  valley. 
This  is  now  the  case  with  the  Westfield,  because  it  has  cut 
down  upon  a  hard-rock  barrier  in  the  trap-ridge  notch ;  and  it 
is  probably  for  this  reason  that  the  lower  section  of  Little  river 
has  swung  so  broadly  and  opened  the  extensive  valley  floor 
already  described  as  forming  the  southern  part  of  the  open 
basin  east  of  Westfield.  Naturally  enough,  then,  the  inclosure 
of  the  broad  valley  floor  on  the  south,  where  Little  river  is 
alone  responsible  for  the  form  of  its  border,  is  nearly  every- 
where a  single  high-scarp  terrace  with  numerous  one-sweep  or 
two-sweep  cusps.  In  other  words,  Little  river  is  swinging  on 
its  present  flood  plain  more  broadly  than  it  has  at  any  earlier 
time  during  the  process  of  degradation.  Second,  whenever  the 
smaller  stream  becomes  superposed  upon  a  rock  barrier,  its 
work  in  the  next  upstream  stretch  proceeds  at  its  own  rate, 
entirely  independent  of  that  of  the  master  stream.  Hence  the 


RIVER  TERRACES  IN  NEW  ENGLAND  573 

valley  floor  in  such  a  stretch  tends  to  widen  and  thus  to  under- 
cut all  the  narrower  flood  plains  formed  in  earlier  stages  of 
degradation.  This  is  the  case  with  both  the  second  and  third 
sections  of  the  Little  river  valley.  It  has  a  well-opened  valley 
floor  usually  inclosed  by  single  terrace  scarps  that  rise  to  the 
full  height  of  the  upper  plain,  so  far  as  I  have  followed  them. 
The  simple  scarps  have  well-developed  reentrants  and  cusps, 
showing  an  active  lateral  swinging  of  the  stream  at  present 
grade,  but  not  giving  indication  of  an  equivalent  swinging  at 
any  higher  flood-plain  level,  and  hence  not  giving  support  to 
the  opinion  that  the  river  is  to-day  of  an  enfeebled  constitution. 

Valley  of  Saxtons  River,  Vermont.  Saxtons  river  enters  the 
Connecticut  from  the  west  at  Bellows  Falls,  Vermont,  and 
shows  a  beautiful  variety  of  terrace  forms  for  some  three  miles 
above  its  mouth.  Figs.  83  and  84,  separated  by  an  unrepre- 
sented interval  of  about  half  a  mile,  give  rough  illustration  of 
these  features.  Careful  survey  would  undoubtedly  show  that 
the  sketch  maps  need  many  changes  in  details,  but  it  is  be- 
lieved that  the  relative  positions  of  terraces,  with  their  free 
and  defended  cusps,  are  shown  with  sufficient  accuracy  for 
the  purposes  of  the  present  discussion.  The  chief  points  here 
illustrated  are  as  follows  : 

Western  Section.  In  the  upstream  or  western  section,  (Fig. 
83),  there  are  numerous  ledges,  but  none  of  them  have  acted 
as  local  base-levels.  The  present  valley  floor  is  graded  with 
respect  to  a  heavy  rock  barrier  a  little  east  of  the  limit  of  Fig. 
83,  and  at  the  western  border  of  Fig.  84.  In  the  three  strong 
ledges  My  Q,  R  (Fig.  83),  on  the  north  side  of  the  valley,  the 
rocks  are  schists,  with  strong  dip  to  the  northeast,  and  hence 
with  bold  outcrops  to  the  southwest.  The  stream  has  swung 
against  the  steep  face  of  these  ledges,  sweeping  them  practically 
free  from  drift  on  the  up-valley  side  down  to  modern  flood-plain 
level,  but  fine  flights  of  stepping  terraces  are  preserved  on  the 
down-valley  side  of  each  ledge,  where  the  trailing  remnants  of 
successive  flood  plains  have  been  defended  from  stream  attack. 
At  least  ten  different  terrace  levels  can  be  counted  adjoining 
ledge  M.  The  third  and  fourth  levels  from  the  top  are  pleas- 
antly shaded  by  a  pine  grove,  and  are  used  as  a  picnic  ground, 


574 


PHYSIOGRAPHIC  ESSAYS 


access  to  which  is  conveniently  given  by  an  electric  railroad  on 
the  valley  floor.  Some  of  these  terraces  may  have  been  carved 
by  a  small  stream  that  here  enters  from  the  north,  but  in  any 

case  they  have  all  been  devel- 
oped with  respect  to  graded 
flood  plains  of  the  main  stream. 
Their  vertical  interval  ranges 
from  five  to  ten  feet,  which 
may  be  taken  here,  as  in  other 
cases,  to  represent  the  amount 
of  deepening  that  the  valley 
floor  suffered  between  two 
northward  swings  of  the 
stream.  The  value  of  the 
ledges  is  most  manifest ;  they 
defended  the  upper  terraces 
from  being  consumed  when 
the  lower  terraces  were  cut 
by  the  returning  stream. 

Ledges  Q  and  R  present 
similar  features  in  flights  of 
eight  and  six  steps,  respec- 
tively. The  river  is  to-day 
swinging  vigorously  against 
the  base  of  ledge  M.  The 
modern  flood  plain  reaches 
the  base  of  Q  and  ft  and  is 
opened  northward  between  M 
and  Q  in  a  space  that  seems 
to  be  comparatively  free  from 
ledges.  The  ledges  here  out- 
cropping on  a  low  terrace  at 
7\f  and  O  seem  to  have  served 
the  double  purpose  of  stopping 
the  northward  swinging  of  the 
main  stream  and  of  limiting  the  east  and  west  swinging  of  the 
side  stream  at  that  level.  I  have  not  closely  examined  the  terraces 
up-valley  from  M,  but  at  least  one  of  the  blunt  cusps  there  seems, 


RIVER  TERRACES  IN   NEW  ENGLAND 


575 


when  seen  from  the  terrace  on  the  opposite  side  of  the  valley, 
to  be  defended  by  a  ledge  at  present  flood-plain  level.  Down- 
valley  from  J?  the  valley  side  is  heavily  wooded  for  quarter  of  a 
mile.  Then  it  closes  in  as  numerous  ledges  and  bowlders  make 
their  appearance  about  S>  near  the  main  road  bridge. 

Low-scarp  terraces  are  wanting  at  high  levels  on  the  south 
side  of  the  valley.  The  upper  plain  descends  by  a  single  strong 
scarp,  twenty  feet  or  more  in  height.  It  presents  a  number  of 


FIG.  84.    PORTIONS  OF  SAXTONS  RIVER  VALLEY,  VERMONT 
(Scale,  about  four  inches  to  a  mile) 

sweeping  reentrants  between  the  defended  cusps  A,  B,  C>  D,  and 
E.  The  A-B  reentrant  is  floored  by  a  rather  uneven  plain  in 
which  several  indistinct  terraces  have  been  cut  on  what  seems 
to  be  at  least  in  part  a  mass  of  till,  for  large  bowlders  are  seen 
thereabout ;  and  this  plain  is  cut  off  in  front  by  two  terraces, 
whose  blunt  cusps  from  F  to  G  appear  to  be  in  part  determined 
by  ledges,  in  part  by  bowlders.  The  small  tributary  stream  that 
crosses  this  reentrant  from  the  south  has  formed  a  fan  on  the 
high  terrace  plain  and  again  on  the  floor  of  the  reentrant,  but  it 


576  PHYSIOGRAPHIC  ESSAYS 

is  now  dissecting  the  fans.  No  B-C  reentrant  has  been  carved 
out,  perhaps  because  till  was  there  discovered.  Several  ledges 
were  encountered  at  lower  levels  between  G  and  //,  against  all 
of  which  the  stream  has  swung  most  faithfully.  The  valley  floor 
would  surely  be  wider  to-day  had  these  ledges  not  existed.  A 
fine  reentrant  was  swept  out  between  the  defended  cusps  C  and 
D  when  the  river  ran  at  a  height  about  ten  feet  over  the  modern 
flood  plain,  and  another  effort  was  here  made  to  widen  the  valley 
floor  at  its  present  level ;  but  as  ledges  are  now  discovered  at 
H  and  /,  farther  forward  than  C  and  D,  the  lower  reentrant  has 
not  quite  consumed  all  of  the  earlier  flood  plain.  A  low  terrace, 
caught  on  ledges  J  and  K,  stands  in  front  of  the  reentrant  be- 
tween D  and  E.  The  projection  of  the  strong  but  low  cusp  at  / 
as  compared  to  that  of  the  blunt  but  high  cusp  at  D  is  one  of 
the  best  illustrations  of  the  effect  of  ledges  that  is  found  in  this 
little  valley.  The  river  must  have  slipped  past  the  ledge  at  Z>, 
as  well  as  past  most  other  defending  ledges  hereabouts  ;  but  a 
compressed  meander  must  have  been  caught  for  a  time  on  the 
ledge  at  J.  Down-valley  from  E  a  modern  swing  of  the  stream 
has  under-cut  all  the  earlier  terraces,  and  a  full-height  scarp  is 
the  result. 

These  terraces  are  even  better  than  those  of  the  Westfield  for 
purposes  of  field  illustration,  inasmuch  as  defended  cusps  here 
occur  in  abundance  on  both  sides  of  the  valley.  The  narrowing 
of  the  interscarp  space,  as  the  valley  floor  was  degraded  to  lower 
and  lower  levels,  is  manifestly  due  to  the  presence  of  the  ledges. 
That  the  river  was  continuously  acting  as  a  graded  but  degrad- 
ing stream  is  sufficiently  proved  by  the  fine  flight  of  stepping 
terraces  at  M.  That  the  preservation  of  the  successive  terraces 
is  not  due  to  any  shrinking  of  the  stream  from  its  first  intention 
as  to  valley  widening  is  proved  by  the  vigor  with  which  it  has 
opened  the  modern  flood  plain  to  as  great  a  width  as  the  nu- 
merous ledges  permit. 

It  was  on  seeing,  in  October,  1900,  the  relation  of  the 
defended  cusp  of  the  little  terrace  at  F  to  the  corresponding 
defended  cusp  of  the  next  higher  terrace  a  little  farther  back  at 
A,  that  the  value  of  ledges  in  determining  terrace  pattern  and 
in  preserving  the  upper  terraces  from  later  attacks  of  the  stream 


RIVER  TERRACES  IN   NEW  ENGLAND  577 

first  came  to  my  mind.  The  manner  in  which  this  explanatory 
idea  first  took  shape  was  as  good  an  example  of  the  sudden 
invention  or  birth  of  theory  as  I  have  ever  experienced,  for  the 
theory  was  essentially  complete  at  the  moment  of  its  first  con- 
scious appearance  ;  since  then  it  has  only  been  confirmed  by 
finding  that  it  had  already  been  born  to  Miller,  and  by  deducing 
its  more  minute  consequences  as  presented  in  Part  III  of  this 
essay  in  order  to  confront  them  with  numerous  examples  of  actual 
terrace  forms,  some  of  which  are  described  on  these  pages. 

Eastern  Section.  The  lower  stretch  of  Saxtons  river  (Fig.  84) 
gives  beautiful  illustration  of  terraces  produced  by  a  stream 
that  has  oscillated  between  two  fixed  nodes.  At  the  upper  node 
the  stream  is  narrowly  held  by  ledges  at  A  and  G.  A  little  far- 
ther upstream  is  a  rocky  gorge  with  cascades,  from  which  the 
stream  is  diverted  for  water  power.  The  lower  valley  becomes 
somewhat  more  open  as  the  space  widens  between  the  ledges  B> 
C,  on  the  south,  and  J-H,  L-K,  on  the  north.  The  small  reen- 
trants between  these  ledges  nearly  everywhere  bear  the  marks 
of  having  been  energetically  swept  back  as  far  as  possible  by  the 
stream  at  various  levels  during  the  erosion  of  the  valley.  The 
stream  has  swung  northward  at  least  nine  times  on  the  J-H 
group  of  ledges,  and  southward  at  least  seven  times  on  the 
B  group,  where  till  seems  to  supplement  the  restraint  of  rock. 

On  leaving  the  cascade  and  the  rapids  below  it,  the  stream  has 
graded  its  course  with  respect  to  the  eastern  rock  node  between 
J/and  F-E\  none  of  the  ledges  encountered  on  the  way  have  had 
other  effect  than  in  limiting  the  breadth  to  which  the  successive 
flood  plains  have  been  opened  during  the  degradation  of  the  valley. 
That  the  degradation  was  gradual,  giving  the  stream  abundant  time 
for  broad  swinging  and  wandering,  right  and  left,  is  abundantly 
proved  by  the  terrace  remnants  of  flood  plains  at  various  levels. 

Passing  the  narrows  at  C,  L-K>  there  is  a  broad  stretch  com- 
paratively free  from  ledges,  until  the  heavy  ridge  of  rock,  M,F-E, 
is  encountered  close  to  the  junction  of  Saxtons  river  with  the 
Connecticut.  The  ridge  is  now  cut  through  by  a  narrow  gorge, 
with  falls  on  the  downstream  side  where  the  road  and  railroad 
bridges  cross  the  stream  ;  whether  this  gorge  is  entirely  the 
work  of  post-glacial  time,  I  cannot  say. 


578  PHYSIOGRAPHIC  ESSAYS 

An  oval  plain,  known  as  the  Basin  farm,  has  been  opened 
between  the  upper  and  lower  narrows,  its  smooth  fields  uniting 
with  the  curving  terrace  scarps  in  a  most  graceful  and  pleasing 
landscape.  The  Basin  plain  probably  had  twice  as  great  an  area 
at  the  level  of  its  mid-height  terraces  as  it  now  has  at  the  level 
of  the  modern  flood  plain  ;  but  this  reduction  of  area  is  not  to 
be  wondered  at,  in  view  of  the  increasing  constriction  imposed 
upon  the  swinging  stream  by  the  mutual  approach  of  the  ledges 
C  and  K  as  lower  and  lower  levels  were  reached. 

A  few  special  features  deserve  mention.  A  southward  deflec- 
tion of  the  stream  from  ledge  K  and  an  increasing  southward 
meander  of  the  stream  in  consequence  of  this  deflection,  with 
a  southward  swinging  of  such  a  meander,  has  probably  been 
responsible  for  some  of  the  large  reentrants  on  the  south  side  of 
the  basin  ;  but  it  is  not  yet  apparent  why  the  reentrants  on  the 
north  should  have  been  repeatedly  worn  farther  from  the  line 
between  the  nodes  than  on  the  south.  The  various  combinations 
of  two-sweep  cusps  in  the  group  of  nine  stepping  terraces  next 
down-valley  from  ledge  C  is  in  every  respect  confirmatory  of  the 
deductions  (p.  544).  It  is  notable  that  remnants  of  terraces  at 
intermediate  heights  form  little  recesses  in  the  cusps  of  later 
origin,  as  might  have  been  expected.  The  terraces  in  the  wooded 
slope  south  of  C  have  riot  been  traced  out ;  but  a  little  farther 
east  four  low-scarped  terraces  rise  at  D  above  the  plain  that  forms 
the  top  of  the  nine-step  flight,  thus  making  a  series  of  thirteen 
steps.  Curiously  enough,  these  four  upper  terraces,  forming  the 
upper  members  of  the  longest  flight  that  I  have  yet  counted, 
swing  northeastward  from  what  seems  to  be  a  free  cusp,  thus, 
apparently  imitating  conditions  similar  to  those  of  Figs.  58  and 
60.  No  ledge  is  visible  in  the  front  of  this  group,  but  as  the 
scarp  of  the  ninth  terrace,  here  descending  to  the  seventh,  also 
bows  a  little  forward  directly  in  front  of  the  apparently  free 
cusp,  I  am  much  inclined  to  think  that  there  is  really  some  de- 
fense here,  now  masked  by  a  slipping  drift  cover.  A  soil  auger 
test  is  proposed  to  settle  this  doubt.  A  detailed  map  of  this 
basin  and  its  terraces  would  be  well. worth  preparing. 

The  Connecticut  below  Bellows  Falls,  Vermont.  The  Connecti- 
cut river  at  Bellows  Falls  is  superposed  on  a  large  body  of  rock, 


FIG.  85.   THE  CONNECTICUT  TERRACES  FROM  BELLOWS  FALLS  TO  WALPOLE 

(Scale,  about  an  inch  and  a  half  -to  a  mile) 

579 


580  PHYSIOGRAPHIC  ESSAYS 

on  whose  down-valley  side  the  river  is  narrowed  in  rushing  cas- 
cades and  rapids.  A  mile  farther  downstream  three  fine  terraces 
are  developed  at  A  (Fig.  85),  on  the  west  side  of  the  valley  just 
below  the  mouth  of  Saxtons  river,  S,  and  all  seem  to  be  defended 
by  ledges  :  the  upper  two  by  ledges  of  the  large  rock  ridge  at  the 
mouth  of  Saxtons  river  (these  are  marked  ^Yin  Fig.  84),  the  low- 
est by  a  ledge  that  stands  several  hundred  feet  farther  forward 
and  is  seen  in  the  railroad  cut  a  quarter  of  a  mile  south  of  Sax- 
tons  river.  (This  group  of  terraces  is  shown  as  seen  from  the 
southeast  in  Fig.  B,  Plate  VIII,  of  Russell's  "  Rivers  of  North 
America.")  A  little  farther  south  the  two  lower  terraces  are 
cut  away  westward  in  the  formation  of  a  broad  valley  floor,  B. 
A  full-height  scarp  rises  at  the  back  border  of  the  floor,  and  near 
its  middle  is  a  blunt  cusp  determined  by  a  strong  ledge.  The 
southern  end  of  this  open  section  of  the  valley  is  inclosed  by  a 
high  free  cusp,  C,  at  whose  apex  the  river  is  now  working.  An- 
other open  valley  floor,  D,  follows  the  free  cusp  and  is  limited 
by  a  second  free  cusp,  E,  of  less  height  but  of  greater  forward 
reach  than  the  first.  The  meaning  of  these  two  free  cusps  will 
be  considered  below. 

Returning  to  Bellows  Falls  and  following  down  the  east  side 
of  the  valley  past  the  entrance  of  Cold  river,  J?,  from  the  north- 
east, ledges  are  found  to  be  more  numerous.  A  broad  mid-height 
terrace  was  opened  until  a  ledge,  F>  was  discovered  in  the  base 
of  the  uppermost  terrace  just  south  of  the  Alstead  road;  the 
farther  southward  extension  of  the  high  terrace  has  not  been 
followed.  The  mid-height  terrace,  followed  by  the  upper  north- 
and-south  road,  was  cut  back  by  a  much  later  swing  of  the  river 
near  present  flood-plain  level,  until  a  high  ledge,  G,  was  discov- 
ered an  eighth  of  a  mile  south  of  Cold  river  :  the  lower  north-and- 
south  road  skirts  its  base.  Nearly  a  mile  farther  south  is  a  group 
of  admirably  defended  terrace  cusps,  If,  up-valley  from  which  the 
river  has  swept  out  some  vigorous  curves,  and  on  one  of  which, 
where  the  mid-height  terrace  first  advances  near  the  Fitch- 
burg  Railroad,  the  river  was  nearly  superposed ;  the  rapids  that 
occurred  here  for  a  time  were  abandoned  as  the  river  slipped  off 
the  northwest  slope  of  the  ledges.  Near  this  point  the  lower 
terrace  advances  to  the  river  bank  on  account  of  the  farther 


RIVER  TERRACES  IN  NEW  ENGLAND  581 

forward  reach  of  other  ledges,  / ;  one  of  them  now  outcrops  in 
the  river  bank  and  thus  insures  the  enduring  protection  of  at  least 
part  of  the  low  plain  on  which  the  railroad  is  here  laid.  It  is 
thus  evident  that  the  meander  belt  of  the  river  has  here  been 
constrained  to  take  a  more  and  more  westward  course  as  it  cut 
deeper  and  deeper,  and  it  is  probably  on  this  account  that  the 
first  large  western  reentrant  below  Saxtons  river  has  been  so 
thoroughly  scoured  out  at  a  low  level. 

The  lower  eastern  terrace  is  gradually  cut  back  down-valley 
from  the  foremost  defending  ledge  ;  and  a  broad,  low  plain,  K,  is 
thus  opened  to  a  half-mile  width,  after  which  it  narrows  towards 
the  bridge  between  Walpole  (W)  a'nd  Westminster  (X).  The  mid- 
height  terrace  continues  down-valley  from  the  abandoned  rapids, 
first  showing  an  apparently  free  two-sweep  cusp  ;  then  a  defended 
cusp,  Z,  the  defending  ledge  of  the  latter  being  disclosed  in  a 
shallow  railroad  cut  at  the  base  of  the  terrace  ;  after  this  the 
terrace  is  cut  some  distance  back  in  a  low-level  reentrant,  inclosed 
by  a  scarp  concave  southward  or  down-valley.  A  little  farther  on 
an  isolated  hill,  M,  traversed  by  the  main  valley  road  and  crowned 
by  a  mansion,  is  separated  from  the  main  slopes  of  the  eastern 
side  of  the  valley  by  a  deep  trench,  ,N,  of  large  sweeping  cur- 
vature to  the  northeast,  and  for  the  most  part  apparently  cut  in 
till.  The  trench  has  a  rather  strong  under-cut  slope  on  the  outer 
side  of  its  curved  course,  and  a  gently  terraced  slope  on  its  inner 
side.  There  can  be  no  doubt  that  it  marks  a  former  path  of  the 
river  around  a  lobate  spur,  and  that  the  river  was  diverted  from 
the  trench  at  a  comparatively  modern,  though  unrecorded,  date 
by  wearing  through  the  narrow  neck  of  the  spur  at  />,  a  little 
upstream  from  Walpole  bridge.  The  second  one,  E,  of  the  two 
free  cusps  above  mentioned  on  the  west  of  the  river,  is  the  uncon- 
sumed  remnant  of  the  neck  of  this  spur,  west  of  the  cut-off ;  the 
isolated  hill,  My  is  the  terminal  part  of  the  spur  northeast  of 
the  cut-off.  The  following  explanation  of  the  relation' between 
the  two  free  cusps  C,  and  E,  may  be  suggested. 

At  an  early  stage  of  the  time  during  which  the  river  was 
making  its  great  northeastward  detour  around  the  spur  EM,  its 
course  may  be  represented  by  the  curve  a,  a,  a,  a.  The  normal 
order  of  change  in  these  curves  would  develop  a  later  course 


582  PHYSIOGRAPHIC  ESSAYS 

by  b,  b,  b,  thus  opening  out  the  two  large  westward  reentrants  B 
and  D,  and  leaving  the  free  cusp  C  as  yet  unconsumed  between 
them.  Had  this  process  been  normally  continued,  the  free  cusp 
C  would  have  been  in  time  worn  away  by  the  down-valley  sweep- 
ing of  the  first  b  meander  ;  but  before  this  was  accomplished,  the 
cut-off  occurred  at  P.  Now  it  may  be  shown  by  a  study  of  the 
detailed  maps  of  the  Mississippi  River  Commission  that  when  a 
cut-off  occurs,  a  systematic  series  of  changes  is  initiated,  and 
that  these  changes  are  extended  upstream  as  well  as  downstream 
from  the  cut-off.  The  essence  of  the  changes  is  such  that  the 
straightening  of  the  course  at  the  cut-off  tends  to  straighten  it 
elsewhere  also,  and  that  this  tendency  is  most  active  near  the 
cut-off  and  weakens  with  distance  from  it.  Following  this  prin- 
ciple, the  course  b,  b,  b,  b  will  be  changed  to  c,  c,  c,  c  and  to  d,  d,  d 
(the  present  channel).  The  river  will  thereby  be  withdrawn  from 
both  of  the  westward  reentrants,  around  whose  up-valley  curves 
it  was  probably  flowing  when  the  cut-off  took  place.  Thus  the 
free  cusp  C  will  be  left  unconsumed  for  a  time  at  least.  It  may 
perhaps  be  possible,  by  accumulating  other  examples  of  changes 
similar  to  this  one,  to  give  some  degree  of  verity  to  the  rather 
hazardous  explanation  here  offered. 

The  Connecticut  below  Turners  Falls,  Massachusetts.  My  field 
notes  here  are  hardly  of  sufficient  detail  to  serve  as  the  basis  of 
a  sketch  map.  Suffice  it  to  say,  that  for  several  miles  down  the 
river  from  Turners  Falls  to  the  Fitchburg  Railroad  bridge  in 
Montague  there  are  numerous  examples  of  defended  terraces, 
fully  confirming  the  principles  already  illustrated  and  suggesting 
some  new  ones,  to  which  I  hope  to  return  in  a  later  essay.  But 
concerning  a  stretch  of  the  river  southward  from  this  section, 
Emerson  has  written  as  follows  : 

The  subsidence  of  the  waters  of  the  Connecticut  lakes  to  the  present 

Connecticut  river  was  very  rapid As  a  result,  one  goes  down  —  through 

the  whole  length  of  the  Montague  Lake,  which  was  well  filled  up  in  the 
flood  time,  except  in  its  southern  portion  —  by  a  great  scarp  to  the  series 
of  erosion  terraces  of  the  modern  river,  the  highest  of  which  rise  but  a  few 
feet  above  the  level  of  the  flood  plain  (725). 

This  conclusion  as  to  the  "  very  rapid  "  change  of  level  by 
which  the  erosion  of  the  present  valley  floor  in  the  former  drift 


RIVER  TERRACES  IN  NEW  ENGLAND  583 

filling  was  initiated,  seems  to  be  based  entirely  on  the  feature 
here  noted,  namely,  the  great  scarp  by  which  descent  is  made 
from  the  high  drift  plain  to  the  low  terraces  of  the  modern 
river.  The  conclusion  is  so  directly  opposed  to  the  one  that  I 
have  reached  in  the  course  of  the  present  study  that  it  has  been 
considered  with  some  care.  In  the  end  I  am  led  to  doubt  its 
validity  for  the  following  reasons : 

First, -the  occurrence  of  the  single  great  scarp  does  not  neces- 
sarily prove  that  the  river  suddenly  cut  its  channel  down  from 
the  level  of  the  "lakes  "  to  about  that  of  the  modern  flood  plain. 
The  single  great  scarp  is  here,  as  in  other  examples  of  the  same 
kind,  perfectly  consistent  with  a  leisurely  degradation  by  the 
river,  and  with  the  production  of  numerous  flood  plains  during 
the  degradation,  provided  only  that  the  modern  swinging  of  the 
river  has  been  greater  than  the  swinging  at  higher  levels,  whereby 
all  remnants  of  the  earlier  flood  plains  shall  have  been  destroyed. 
It  has  been  shown  that  this  is  habitual  with  a  number  of  streams 
wherever  they  are  free  to  swing  in  loose  drift  of  fine  texture  ;  and 
it  appears  from  Emerson's  description  that  such  was  the  case 
with  the  Connecticut  while  it  was  sweeping  away  the  fine  silts 
of  the  Montague  "  lakes." 

Second,  the  leisurely  lateral  swinging  of  Saxtons  and  Westfield 
rivers  at  high  levels,  as  recorded  by  the  upper  members  of  the 
terrace  flights  in  the  valleys  of  those  tributaries  of  the  Connecti- 
cut, show  that  they  were  not  hurried  in  the  early  stages  of  their 
work  of  degradation ;  yet  hurried  they  must  have  been,  had  the 
master  river  suddenly  intrenched  itself  in  the  weak  drift  filling 
of  its  aggraded  valley.  There  are,  to  be  sure,  certain  rock  and 
till  barriers  between  these  terrace  flights  and  the  junction  of 
their  streams  with  the  Connecticut,  and  such  barriers  might 
separate  a  quickly  degrading  trunk  river  from  slowly  degrading 
tributaries ;  but  it  is  believed  that  the  barriers  are  too  low  to 
have  been  encountered  until  after  the  high-level  terraces  had 
been  carved. 

Third,  there  are  certain  points  where  the  Connecticut  itself 
exhibits  stepping  terraces  at  altitudes  of  at  least  eighty  or  more 
feet  above  its  present  level.  The  best  of  these  are  at  East 
Deerfield,  two  miles  south  of  Turners  Falls,  where  the  Fitchburg 


584  PHYSIOGRAPHIC  ESSAYS 

Railroad  crosses  a  group  of  terraces  between  the  mouth  of  the 
Deerfield  and  the  east-south  bend  of  the  Connecticut.  Here  an 
eastern  profile  from  the  high  terrace  south  of  the  railroad  station 
to  the  river  crosses  five  terraces,  the  height  of  whose  scarps  I 
have  estimated  at  30,  25,  15,  18,  and  35  feet  (total,  123  feet).  If 
the  profile  be  taken  northward  from  the  high  terrace,  seven 
scarps  are  passed,  including  the  descent  from  the  lowest  plain  to 
the  river,  with  heights  estimated  at  30,  25,  10,  5,  15,  10,  and  15 
feet  (total,  no  feet).  The  locality  of  these  terraces  is  openly 
connected  with  that  of  the  high  scarps  in  the  Montague  silts ; 
and  hence  a  leisurely  process  of  degradation  with  repeated  lateral 
swinging  is  probable  there  as  well  as  here.  The  only  essential 
difference  between  the  two  localities  is  that  the  terraces  are  for 
good  reason  preserved  in  East  Deerfield,  where  the  river  has 
become  increasingly  constrained  by  successive  discoveries  of 
sandstone  ledges,  while  they  have  been  destroyed  farther  south, 
where  the  river  has  been  free  to  swing  at  modern  levels. 

The  Connecticut  near  Springfield,  Massachusetts.  There  are 
few  ledges  exposed  hereabouts  and  few  stepping  terraces.  The 
high  terrace  that  is  nearly  continuous  on  the  east  side  of  the 
valley  from  Springfield  up  to  Chicopee  is  now  swept  by  the  river 
for  a  part  of  its  length,  and  within  this  stretch  a  sandstone  ledge 
is  seen  in  the  river  bank.  In  the  southern  part  of  Springfield 
there  are  several  ledges  and  some  exposures  of  bowldery  till,  by 
which  the  opening  of  the  valley  to  the  east  has  been  restrained, 
and  a  little  farther  south,  by  the  mouth  of  Pecowsic  brook,  a 
strong  ledge  deflects  the  river  to  the  southwest. 

No  ledges  are  found  in  the  terrace  scarps  on  the  western  side 
of  the  valley  hereabouts,  although  several  rather  well-formed 
cusps  project  forward  towards  the  river :  one  at  the  grounds  of 
the  Country  Club,  another  at  the  old  meetinghouse  north  of 
West  Springfield,  and  a  third  between  West  Springfield  and  the 
Agawam.  The  Westfield  river  enters  the  main  valley  in  the 
reentrant  between  the  second  and  third  cusps,  while  south  of 
the  third  cusp  the  Connecticut  has  repeatedly  scoured  out  reen- 
trants, from  which  it  has  been  withdrawn  by  short-cuts  or  cut- 
offs. I  am  inclined  to  think  that  the  Connecticut  has  been  pushed 
eastward  by  the  action  of  the  Westfield  ;  that  it  has  therefore 


RIVER  TERRACES  IN  NEW  ENGLAND  585 

repeatedly  swung  westward  from  the  Pecowsic  ledges,  and  that 
the  Agawam  reentrants  are  thus  to  be  explained.  If  so,  they  fall 
into  the  same  class  with  those  of  the  Westfield  in  the  reentrant 
next  west  of  the  trap-ridge  notch.  The  southernmost  of  the  three 
free  cusps  on  the  west  side  of  the  Connecticut  valley,  below  the 
entrance  of  the  Westfield,  would  thus  correspond  with  the  free 
cusp  on  the  south  side  of  the  Westfield,  below  the  entrance  of 
Little  river.  The  other  free  cusps  of  the  Connecticut  may  perhaps 
come  to  find  an  explanation  in  a  process  similar  to  that  suggested 
for  the  free  cusps  between  Bellows  Falls  and  Westminster. 

There  is  nothing  in  this  stretch  of  the  river  to  suggest  a 
significant  diminution  of  volume  since  terracing  began.  The 
frequent  occurrence  of  high  single  scarps  would,  on  the  other 
hand,  suggest  that  the  river  is  to-day  [demanding  a  breadth  of 
swinging  as  great  as  or  greater  than  it  ever  did  before. 

The  Merrimac  between  Concord  and  Manchester,  New  Hamp- 
shire. The  Merrimac,  near  Concord,  has  opened  a  broad  flood 
plain,  on  which  a  number  of  former  meanders  are  now  repre- 
sented by  oxbow  lakes.  On  the  east  the  plain  is  commonly 
bounded  by  a  single  high  scarp,  which  the  river  is  actively  under- 
cutting at  one  point.  On  the  west  there  is  a  single  high  scarp 
bordering  part  of  the  plain  north  of  the  city;  but  a  few  ledges 
appear,  and  the  scarp  is  divided  into  several  terraces  as  the  city 
is  entered.  Passing  down  the  valley  (southward)  ledges  appear 
more  frequently,  the  breadth  of  the  flood  plain  gradually  de- 
creases, and  terraces  appear  in  increasing  numbers.  The  valley 
about  Concord  is  one  of  the  best  examples  for  illustration  of  the 
capacity  of  an  unconstrained  river  to  open  a  broad  flood  plain 
inclosed  by  strong  scarps,  as  typified  in  Figs.  45  and  65  ;  while 
farther  south  the  valley  exhibits 'the  complete  control  exercised 
upon  a  swinging  river  by  the  chance  discovery  of  ledges  during 
the  progress  of  degradation.  This  process  is  shown  to  have 
been  gradual  by  the  preservation  of  flood-plain  remnants  at  vari- 
ous heights,  wherever  ledges  are  present  to  defend  their  bases  ; 
yet  so  complete  is  the  destruction  of  the  plains  at  intermediate 
levels  just  above  Concord  that  one  might  there  infer  that  the 
river  had  had  no  opportunity  to  swing  laterally  until  the  opening 
of  the  present  flood  plain  was  begun. 


586  PHYSIOGRAPHIC  ESSAYS 

REFERENCES 

Adams,  C.  B.  Second  Annual  Report  on  the  Geology  of  the  State  of  Ver- 
mont (1846). 

Davis,  W.  M.  "The  Drainage  of  Cuestas."  Proc.  Geol.  Assoc.  (London), 
XVI  (1899),  75-93- 

Diller,  J.  S.  "  Westfield  during  the  Champlain  Period."  Am.  Jour.  Set., 
XIII  (1877),  262-265. 

Emerson,  B.  K.  "  Geology  of  Old  Hampshire  County,  Massachusetts." 
U.  S.  Geol.  Surv.,  Mon.  ' XXIX  •{*&&• 

Gilbert,  G.  K.  Report  of  the  Geology  of  the  Henry  Mountains.  Wash- 
ington, 1877. 

Hitchcock,  E.  "  Illustrations  of  Surface  Geology."  Smithsonian  Contribu- 
tions to  Knowledge  (1857). 

Miller,  H.  "River  Terracing:  its  Methods  and  their  Results."  Proc. 
Roy.  Phys.  Soc.  (Edinburgh),  VII  (1883),  263-305. 

Playfair,  J.    Illustrations  of  the  Huttonian  Theory  of  the  Earth  (1802). 

Shaler,  N.  S.  "  Fluviatile  Swamps  of  New  England."  Am.  Jour.  Sci., 
XXXIII  (1887),  210-221. 


XXII 
THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE 

The  Three  Rivers.  The  narrow  basin  of  the  Meuse  lies 
between  the  widespreading  branches  of  the  Seine  on  the  west 
and  of  the  Moselle  on  the  east.  The  slender  trunk  stream  of 
the  Meuse,  with  hardly  a  tributary  on  either  side,  is  like  one 
of  those  tall,  closely  trimmed  poplars  that  the  traveler  often  sees 


FIG.  86 

along  the  national  roads  of  France,  and  the  comparison  is  not 
altogether  inapt,  for  there  is  good  reason  to  think  that  the 
Meuse  has  really  been  trimmed  of  certain  branches  which  have 
been  diverted  to  the  basins  of  its  larger  neighbors.  Its  basin 
is,  indeed,  like  the  dwindling  territory  of  a  petty  prince  be- 
tween the  encroaching  kingdoms  of  powerful  rulers  on  either 
side.  The  evidence  of  this  will  appear  when  we  examine  the 
characteristics  of  the  three  rivers. 

587 


588  PHYSIOGRAPHIC   ESSAYS 

The  Vigorous  Meanders  of  the  Seine.  The  Seine,  after  gather- 
ing in  its  upper  branches  both  above  and  below  Paris,  pursues 
a  strongly  meandering  course  to  the  sea.  Its  lower  valley  is 
sunk  with  rather  steep  sides  in  a  comparatively  even  upland, 
which  itself  is  a  surface  of  denudation.  Although  without  com- 
plete proof  on  this  point,  I  am  led  to  suppose  that  this  gently 
rolling  upland  is  an  uplifted  peneplain,  that  is,  a  denuded 
region  that  was  once  reduced  to  a  surface  of  moderate  relief 
close  to  its  controlling  base-level  and  then  raised  by  some 
gentle  process  of  elevation  to  its  present  altitude.  During  the 
development  of  the  peneplain  the  Seine,  the  master  river  of 
the  region,  must  have  attained  an  extremely  faint  grade,  and  at 
the  same  time  have  taken  on  the  habit  of  swinging  from  side  to 
side  in  comparatively  regular  curves  or  meanders  such  as  are 
characteristic  of  rivers  with  gentle  slope.  With  the  uplift  of 
the  region  the  meandering  river  would  proceed  to  incise  its 
channel  beneath  the  uplifted  surface,  and  thus  Ramsay  accounted 
for  its  peculiar  intrenched  meanders  many  years  ago.  They  seem 
to  be  features  oi  old  age  retained  in  youth  of  the  present  cycle 
of  denudation  as  an  inheritance  from  an  advanced  stage  of  a 
preceding  cycle. 

In  the  second  cycle  of  denudation,  now  in  progress,  the  belt 
of  country  inclosed  by  lines  tangent  to  the  outer  meander 
curves  of  the  Seine  seems  to  have  broadened  to  greater  width 
than  it  possessed  before  the  uplift  of  the  region  occurred.  The 
evidence  of  this  is  seen  in  the  long  sloping  descent  of  each 
tongue  of  land  which  enters  one  of  the  river  curves  and  from 
which  the  river  seems  to  have  receded,  while  the  outer  side  of 
the  swinging  current  under-cuts  a  bluff  of  steep  descent  from 
the  upland,  as  if  the  river  were  pressing  against  it.  The  great 
curves  around  which  the  river  swings  fit  in  nearly  all  cases 
close  to  the  bluff  on  their  outer  side.  It  is  an  able-bodied  river, 
a  river  of  a  robust  habit  of  life. 

The  Case  of  the  Ste.  Austreberte.  Not  far  below  the  city  of 
Rouen  and  precisely  at  the  small  town  of  Duclair,  on  the  north 
bank  of  the  Seine,  there  is  an  interesting  little  occurrence  strongly 
confirmatory  of  the  invigorated  habit  of  the  swinging  river. 
Duclair  is  situated  on  the  outer  side  of  a  large  north-turning 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     589 

meander.  Into  this  north-turning  meander  descends  a  long  slop- 
ing spur  from  the  upland  south  of  the  river ;  east  and  west  of 
Duclair  similar  long  sloping  spurs  descend  from  the  northern 


FIG.  87.   VALLEY  OF  THE  SEINE,  NEAR  DUCLAIR 

upland  into  the  adjacent  south-turning  meanders.  On  looking 
closely  at  the  map  of  the  country  or,  still  better,  on  looking 
over  the  region  itself  from  the  top  of  the  bluff  at  the  back  of 


590 


PHYSIOGRAPHIC  ESSAYS 


the  town,  it  is  seen  that  the  western  of  the  two  northern  spurs  is 
obliquely  cut  across  by  a  narrow,  dry,  flat-bottomed  valley,  which 
is  just  in  continuation  of  the  course  of  a  little  stream  known  as 
the  Ste.  Austreberte,  coming  from  the  northeast  and  mouthing 
in  the  Seine  at  Duclair.  The  dry  valley  was  evidently  at  one 
time  followed  by  the  lower  course  of  this  stream,  and  it  is  still 
followed  by  the  highway  and  the  railway,  for  which  it  serves  for 
a  short-cut  on  their  way  down  the  Seine  (Fig.  87). 

The  question  then  arises,  Why  has  the  stream  deserted  so 
well-prepared  a  path  ?  The  answer  is  not  far  to  seek.  The 
change  evidently  occurred  because  the  Duclair  meander  of  the 
Seine  pushed  its  inclosing  bluff  farther  and  farther  north  until 
the  river  cut  through  the  ridge  that  separated  it  from  the  Ste. 
Austreberte  and  thus  tempted  that  stream  to  desert  its  lower 
course.  This  little  fact,  taken  in  connection  with  the  slopes  of 
the  dove-tailing  spurs,  fully  justifies  the  opinion  that  the  Seine 
is  a  most  vigorous  river,  not  only  competent  to  swing  around 
the  curves  of  its  former  meanders,  but  demanding  an  increased 
radius  for  every  curve,  and  thus  widening  its  meander  belt. 
Here  and  there,  it  is  true,  the  swinging  course  of  the  river 
departs  somewhat  irregularly  from  the  round  curves  of  its 
valley,  as  if  the  river  had  shrunk  away  somewhat  from  the 
strong  curves  which  it  once  followed.  This  may  perhaps  be 
explained  as  the  result  of  the  diminishing  velocity  of  the  river, 
now  that  it  has  cut  its  new  valley  deep  below  the  adjacent 
upland  and  close  to  the  controlling  base-level,  but  the  irregulari- 
ties are  exceptional  and  they  need  not  be  further  considered. 
As  a  whole,  the  river  may  be  regarded  as  an  able-bodied  stream 
turning  vigorously  from  curve  to  curve  on  its  way  to  the  sea. 

The  Robust  Habit  of  the  Moselle.  Let  us  next  glance  at  the 
lower  course  of  the  Moselle.  Passing  below  its  upper  branching 
course  and  following  it  below  Treves  through  the  highlands  to 
the  Rhine,  we  find  here  again  a  most  serpentine  valley  incised 
beneath  the  general  upland  of  the  region.  Ascending  from  the 
valley  bottom,  which  the  traveler  ordinarily  follows,  to  the 
level  of  the  inclosing  upland,  it  is  even  more  manifest  here 
than  in  northwestern  France  that  we  have  to  do  with  an  uplifted 
and  well-dissected  peneplain.  The  surrounding  region  is  one  in 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     59! 

which  the  rocks  are  greatly  deformed,  possessing  all  the  charac- 
teristics of  mountain  structure,  but  few  of  the  characteristics  of 
mountain  height.  Indeed,  the  upland  between  Treves  and  the 
Rhine  is  one  of  the  best  examples  of  an  uplifted  peneplain  that 
I  have  seen.  The  gently  rolling  surface  shows  little  regard  for 
the  great  diversity  in  the  attitude  of  its  rocks.  Here  and  there 
it  is  still  surmounted  by  low,  linear  eminences,  such  as  the  Idar- 
wald  and  the  Soonwald,  following  the  strike  of  resistant  quartz- 
ites.  These  I  would  call  "  monadnocks,"  taking  the  name  from  a 
typical  residual  mountain  which  surmounts  the  uplifted  peneplain 
of  New  England  in  southwestern  New  Hampshire. 

But  how  has  the  Moselle  come  to  follow  a  meandering  valley 
deeply  incised  in  the  peneplain  ?  It  is  manifest,  from  what  is 
now  known  concerning  the  geological  development  of  land  sur- 
faces, that  during  the  later  stages  of  the  denudation  of  the  mid- 
dle Rhine  highlands  the  streams  of  the  region  must  have  flowed 
idly  along  meandering  courses  with  gentle  slope  in  channels 
little  below  the  surrounding  surface  ;  but  at  present  the  streams, 
and  especially  the  master  rivers  of  the  region,  have  deeply  in- 
cised courses  inclosed  by  steep-sided  valleys.  Clearly,  then,  the 
region  has  been  uplifted  since  the  denudation  of  the  peneplain 
and  is  now  well  entered  in  a  second  cycle  of  denudation.  The 
meanders  developed  in  the  later  stages  of  the  previous  cycle  of 
denudation  are  inherited  in  the  early  stage  of  the  present  cycle. 

It  is  worth  noting,  however,  that  there  seems  to  have  been 
a  pause  during  the  general  elevation  of  the  region,  for  the  val- 
ley of  the  Moselle  may  be  described  as  a  narrow,  meander- 
ing trench  cut  in  a  wide-open,  flat-bottomed  trough,  the  trough 
being  sunk  well  beneath  the  general  surface  of  the  adjacent 
upland.  The  same  sequence  of  forms  may  be  clearly  recognized 
in  the  valley  of  the  Rhine,  particularly  in  the  neighborhood  of 
Bacharach,  where  the  old  river  alluvium  still  lies  on  the  floor 
of  the  uplifted  trough,  although  the  existing  river  trench  is 
sunk  several  hundred  feet  beneath  it.  It  must  therefore  be 
concluded  from  the  relation  of  the  upland,  the  trough,  and  the 
trench  that  the  uplift  of  the  region  to  its  present  height  was 
accomplished  in  two  movements,  and  that  a  longer  interval  of 
comparative  rest  followed  the  first  movement  than  has  yet 


592  PHYSIOGRAPHIC  ESSAYS 

elapsed  since  the  second ;  but  it  must  also  be  understood  that 
the  time  that  has  elapsed  from  the  first  of  these  movements  to 
the  present  day  is  very  short  compared  to  the  long  cycle  of 
denudation  during  which  the  ancient  mountains  of  the  region 
were  worn  down  to  the  general  surface  of  the  peneplain. 

The  meanders  which  the  Moselle  now  follows  in  its  serpen- 
tine trench  are  therefore  to  be  regarded  as  the  inheritance  of  a 
meandering  habit  that  it  acquired  on  the  floor  of  the  trough, 
but  here,  as  in  the  case  of  the  Seine,  the  present  width  of  the 
meander  belt  is  somewhat  greater  than  the  width  of  the  former 
belt,  judging  from  the  difference  in  the  slopes  of  the  interior 
spurs  and  the  steep  bluffs  opposite  them  on  the  outer  side  of 
the  river  curves.  The  Moselle,  like  the  Seine,  swings  around 
its  curves  with  a  robust,  full-bodied  action,  nowhere  hesitating 
to  make  the  circuit  with  strong  pressure  on  its  outside  bank. 

The  Two  Cut-offs  above  BerncasteL  At  several  points  the 
spurs  from  the  upland  have  very  narrow  necks  through  which 
the  valley  railway  passes  in  short-cut  tunnels.  Although  I  have 
not  found  any  example  of  the  diversion  of  a  side  stream  by 
the  lateral  growth  of  the  river  meanders,  yet  such  a  change 
is  imminent  just  above  Piinderich,  where  the  ridge  between  the 
Moselle  and  the  Alfbach  is  reduced  to  a  very  narrow  measure. 
But  it  does  appear  that  just  above  Berncastel  the  Moselle  has 
played  upon  itself  the  same  trick  that  the  Seine  has  played 
upon  the  Ste.  Austreberte.  The  Moselle  at  this  point  has  an 
exceptionally  straight  course,  but  to  the  right  and  left  of  it 
rise  two  isolated  hills,  inclosed  by  troughs  of  horseshoe  shape 
whose  outer  slopes  rise  to  the  general  uplands.  From  the 
study  of  the  maps  at  home  I  had  come  to  the  opinion  that 
these  troughs  represented  former  meanders  of  the  river,  now 
abandoned  in  favor  of  the  more  direct  intermediate  course,  and 
an  inspection  of  the  district  on  the  ground  has  confirmed  this 
belief.  (See  Fig.  88.) 

Nothing  can  be  more  satisfactory  than  the  agreement  shown 
between  the  features  of  these  abandoned  meanders  and  of  the 
meanders  still  occupied  by  the  river  farther  down  the  trench. 
The  radius  of  curvature  is  essentially  the  same  in  the  several 
cases.  The  slopes  on  the  outsides  of  the  troughs  have  the 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     593 


FIG.  88.   VALLEY  OF  THE  MOSELLE,  NEAR  BERNCASTEL 

characteristic,  bluff-like  descent  from  the  upland.  The  isolated 
hills  are  the  ends  of  interlocking  spurs,  now  dissevered  from 
the  uplands  by  the  cross-cut  of  the  river ;  the  ends  of  these  hills 
that  project  into  the  horseshoe  troughs  have  the  comparatively 


594 


PHYSIOGRAPHIC  ESSAYS 


gentle  descent  of  the  spurs  that  are  elsewhere  found  projecting 
into  the  actual  meanders.  Not  only  so ;  the  eastern  branch  of 
the  southern  horseshoe  is  just  opposite  and  in  line  with  the 
western  branch  of  the  northern  horseshoe.  There  can  be  no 
doubt  that  the  vigorous  Moselle  has  here  so  earnestly  swung 
against  its  outer  bank  that  it  has  actually  shortened  its  own 
course  by  cutting  through  the  narrow  necks  of  the  intervening 
spurs.  Perhaps  I  am  giving  too  much  emphasis  to  this  occur- 
rence. It  is  not  a  great  rarity,  for  similarly  abandoned  river 
meanders  are  not  infrequent  in  other  plateaus.  They  are  known 
in  the  plateau  of  Wiirtemberg,  where  it  is  trenched  by  the 
Neckar  at  Lauffen  and  just  above,  and  in  the  plateau  of  western 
Pennsylvania,  trenched  by  the  Ohio  and  its  branches.  It  is  not, 
however,  the  mere  occurrence  of  these  cut-off  meanders,  but 
rather  the  lesson  that  they  teach,  that  deserves  emphasis.  They 
all  indicate  strong  river  action.  The  Moselle  must  therefore  be 
regarded  as  an  able-bodied,  vigorous  river,  like  the  Seine. 

The  Staggering  Meiise.  Let  us  now  look  at  the  Meuse. 
From  some  distance  above  Commercy,  downstream  as  far  as 
Verdun  and  beyond,  this  river,  like  the  others,  follows  a  well- 
defined  meandering  valley,  incised  beneath  uplands  on  either 
side.  As  before,  the  slope  of  the  bluffs  on  the  outer  side  of  the 
valley  curves  is  comparatively  steep,  while  the  slope  of  the 
spurs  on  the  inner  side  of  the  curves  is  relatively  gentle.  Just 
above  Commercy,  near  Sorcy-sur-Meuse,  one  of  the  spurs  is 
almost  cut  through  and  is  now  connected  with  its  upland  by  a 
very  narrow  and  low  neck,  which  alone  separates  the  flood 
plain  of  the  curving  valley  on  either  side.  The  railway  and 
canal  both  save  distance  by  cutting  across  the  low  neck.  At 
Dun-sur-Meuse  the  neck  of  a  former  spur  is  entirely  cut  through. 
It  now  stands  as  an  isolated  hill  surrounded  on  all  sides  by  the 
flat  valley  floor. 

It  is  manifest,  then,  that  this  valley  was  excavated  by  a  river 
hardly  less  vigorous  than  those  that  cut  the  valleys  of  the 
Seine  and  the  Moselle,  but  the  vigorous  river  that  was  once 
here  is  now  nowhere  to  be  found.  The  floor  of  the  valley  is  at 
present  occupied  for  the  most  part  by  broad,  green  meadows, 
instead  of  by  a  free-swinging  current  of  water,  and  the  only 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     595 


FIG.  89.  VALLEY  OF  THE  MEUSE,  NEAR  ST.  MIHIEL 

stream  to  be  found  is  the  little   Meuse,   wandering  here  and 
there  on  the  broad  meadows  and  staggering  with  most  uncertain 


596  PHYSIOGRAPHIC  ESSAYS 

step  around  the  valley  curves.  It  wriggles  from  place  to  place, 
now  touching  this  side  of  the  valley,  now  that,  swinging  in- 
differently against  the  steep  bluffs  and  gentle  slopes  of  the 
spurs,  sometimes  even  running  for  a  short  distance  up  the  val- 
ley in  its  irregular  path.  Is  it  not  then  clear  that  since  the 
time  when  this  winding  valley  was  made  there  has  been  a  great 
diminution  in  the  volume  of  water  that  follows  it  ?  No  other 
conclusion  seems  admissible  ;  and  hence  a  reason  for  the  loss 
of  volume  must  be  sought.  (See  Figs.  89  and  90.) 

The  loss  of  volume  cannot  be  ascribed  to  any  climatic  change, 
for  that  should  have  affected  the  Seine  and  Moselle  as  well. 
May  it  then  be  ascribed  lo  a  change  of  the  area  drained, 
whereby  the  Seine  and  the  Moselle  gained  the  drainage  area 
which  the  Meuse  lost  ?  If  "this  were  so,  the  Meuse  would  have 
become  smaller  and  smaller,  while  the  Seine  and  Moselle  grew 
larger  and  larger.  The  dwindling  Meuse  would  have  lost  the 
power  of  swinging  boldly  around  its  valley  curves  ;  it  would 
have  fallen  into  the  present  timid  habit  of  staggering,  after 
the  fashion  of  other  small  streams,  but  at  the  same  time  the 
Seine  and  the  Moselle  would  have  been  confirmed  in  their 
vigorous  habit  of  swinging  freely  around  the  curves  of  their 
valleys.  Is  it  possible,  then,  that  the  side  branches  of  the 
Meuse  have  really  been  trimmed  from  the  trunk  river,  and 
that  the  trimmed  branches  have  been  engrafted  into  the  sys- 
tems of  the  Seine  and  the  Moselle  ? 

The  Migration  of  River  Divides.  The  question  thus  raised 
leads  to  a  consideration  of  the  general  problem  of  the  shifting  or 
migration  of  river  divides,  a  subject  that  is  of  particular  interest 
to  the  student  of  physical  geography.  At  first  sight  one  would 
be  inclined  to  think  that  the  crest  line  of  a  divide  between  adja- 
cent river  basins  would  merely  waste  lower  and  lower  as  it 
weathered  away,  without  shifting  laterally,  and  therefore  without 
causing  any  change  in  the  area  of  the  adjacent  drainage  basins. 
It  is  probable,  however,  that  this  simple  process  is  of  very  rare 
occurrence  in  nature.  It  is  much  more  likely  that  the  line  of  the 
divide  will  move  more  or  less  to  one  side  or  the  other  .as  it 
weathers  away,  on  account  of  the  unequal  rate  of  wasting  of  its 
two  slopes.  The  possible  causes  of  unequal  wasting  are  various. 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     597 


annevoox 


FIG.  90.   VALLEY  OF  THE  MEUSE,  NEAR  DUN-SUR-MEUSE 

The  declivity  of  the  two  slopes  may  differ,  in  which  case  the  steep 
slope  wastes  faster  than  the  other,  and  the  divide  is  very  slowly 
pushed  toward  the  natter  slope.  The  rocks  underlying  the  two 
slopes  may  be  of  different  resistance  ;  then  the  weaker  one  will, 


598  PHYSIOGRAPHIC  ESSAYS 

as  a  rule,  waste  away  the  faster,  and  the  divide  will  gradually 
migrate  toward  the  more  resistant  rocks.  Again,  the  agencies  of 
erosion  may  be  of  different  activities  on  the  two  slopes  ;  one 
slope  may  have  a  greater  rainfall  than  the  other,  or  may  suffer  a 
greater  number  of  alterations  from  freezing  to  melting.  Although 
the  last  is  generally  a  subordinate  cause,  it  probably  contributes 
in  a  small  way  to  the  solution  of  the  problem  as  a  whole. 

The  shifting  of  the  divide,  as  thus  explained,  is  generally 
accomplished  by  a  slow  migration.  In  some  cases,  however, 
when  the  divide  is  pushed  to  the  very  side  of  a  stream  whose 
basin  it  inclosed,  then  a  little  further  change  diverts  all  the 
upper  drainage  of  this  stream  into  the  encroaching  basin,  and 
with  this  change  the  divide  makes  a  sudden  leap  around  the 
upper  waters  of  the  diverted  river,  after  which  the  slow  migra- 
tion may  be  resumed.  The  movement  of  a  divide  may  there- 
fore be  described  as  alternately  creeping  and  leaping. 

Whether  this  process  is  of  very  general  importance  or  not 
can  hardly  be  decided  at  the  present  time,  but  there  are  cer- 
tain regions  in  which  its  application  is  most  illuminating  to  the 
studies  of  the  physical  geographer.  Philippson  has  brought  the 
subject  to  general  attention  in  his  "Studien  iiber  Wassercheiden," 
where  a  full  account  of  what  others  have  done  up  to  1885  may 
be  found.  Oldham  has  told  how  certain  headwaters  of  the 
Indian  rivers  are  pushing  their  divides  through  the  innermost 
of  the  Himalayan  ranges,  and  thus  acquiring  drainage  area 
that  formerly  belonged  to  the  interior  streams  of  the  elevated 
Tibetan  plateau.  This  example  is  one  of  the  best  in  which  the 
process  depends  chiefly  on  the  unequal  declivity  of  the  slopes 
on  the  two  sides  of  the  divide.  Heim  has  described  the  dep- 
redations of  the  Maira  in  beheading  the  upper  course  of  the 
Inn,  thus  accounting  in  a  most  beautiful  manner  for  the  little 
lakes  at  the  head  of  the  Engadine  valley,  where  this  contest  is 
going  on.  The  special  map  of  the  Ober-Engadine,  published  in 
1889,  on  a  scale  of  i  :  50,000,  by  the  Swiss  topographical 
bureau,  gives  fine  illustration  of  the  significant  features  of  river 
interaction  in  this  region. 

A  remarkable  case  of  river  diversion  occurs  in  the  shift  of  the 
course  of  the  Vistula  from  its  former  path  down  the  valley  now 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     599 

occupied  by  the  Netze  to  a  more  northward  course,  by  which  it 
flows  directly  to  the  Baltic  sea,  the  point  of  change  being  at  the 
town  of  Bromberg.  This  is  well  illustrated  on  the  Prussian  topo- 
graphical maps,  and  has  been  described  in  a  general  way  by  vari- 
ous writers  on  the  geography  of  north  Germany.  Whether  it 
was  caused  by  the  spontaneous  interaction  of  streams  competing 
for  drainage  area  or  not,  I  shall  not  at  this  distance  venture  to 
say,  but  shall  hope  to  find  a  full  explanation  of  the  change  in  a 
forthcoming  essay  by  Berendt.  Jukes-Brown  has  described  an 
interesting  case  in  England,  where  the  Trent  captured  the  head- 
waters of  the  Wytham,  and  in  a  volume  of  the  Geographical 
Journal  of  London  I  have  attempted  a  more  general  treatment 
of  the  same  region.  Readers  who  wish  to  follow  the  subject  into 
examples  of  greater  intricacy  may  find  some  problematical  ex- 
amples in  the  rivers  of  Pennsylvania  and  northern  New  Jersey. 

In  the  general  discussion  of  this  problem  we  should  recognize 
two  divisions  :  first,  the  processes  by  which  it  is  accounted  for, 
these  having  just  been  summarily  described  ;  second,  the  topo- 
graphical forms  by  which  its  occurrence  may  be  recognized,  dis- 
tinction being  made  between  examples  occurring  in  the  remote 
or  the  recent  past  and  others  likely  to  occur  in  the  near  or  distant 
future.  Illustration  of  the  second  division  of  the  subject  can  best 
be  given  by  describing  the  concrete  case  of  the  river  Marne  near 
Chalons,  than  which  no  better  example  has  come  to  my  notice 
anywhere  in  the  world  (see  Fig.  92). 

The  Case  of  the  Marne  below  Chalons.  In  the  province  of 
Champagne  the  Marne  drains  an  extended  interior  lowland  in- 
closed by  a  forested  upland  on  the  west.  The  lowland  is  the 
product  of  comparatively  rapid  erosion  during  late  Tertiary  time 
on  weak  upper  Cretaceous  strata.  It  is  for  the  most  part  covered 
by  extensive  farms.  The  upland  stands  where  the  lower  Tertiary 
strata  have,  during  the  same  period  of  time,  more  successfully 
resisted  erosion.  As  the  dip  of  the  strata  is  gently  westward, 
the  eastern  margin  of  the  upland  is  marked  by  a  steep  escarp- 
ment. The  Marne  gathers  many  branches  from  the  lowland  and 
escapes  on  its  way  to  the  sea  by  a  deep  valley  cut  through  the 
upland.  In  this  valley  it  receives  two  branches  on  the  south- 
ern side,  to  which  special  attention  should  be  given.  The  first  is 


600  PHYSIOGRAPHIC  ESSAYS 

the  Surmelin,  whose  head  is  found  in  the  upland  near  its  eastern 
precipitous  margin  ;  but,  curiously  enough,  although  this  stream 
of  course  diminishes  toward  its  source  near  Montmort,  the  valley 
that  it  occupies  maintains  an  almost  constant  width  some  six 
miles  farther,  nearly  to  the  escarpment  of  the  upland.  The  sec- 
ond branch  is  the  Petit  Morin.  This,  like  the  Marne,  heads  in 
the  lowland  east  of  the  upland,  and  also,  like  the  Marne,  escapes 
by  a  deep  and  narrow  valley  through  the  upland.  The  lowland 
area  that  it  drains  is,  however,  very  small,  and  for  about  ten 
miles  from  its  head  there  is  an  extended  marsh,  known  as  the 
Marais  de  St.  Gond,  lying  partly  on  the  lowlands  and  partly  in 
the  entrance  to  the  narrow  valley  in  the  upland. 

In  searching  for  a  reason  for  this  arrangement  of  the  Marne 
and  its  two  branches,  it  is  important  to  notice  that  if  the  branches 
were  prolonged  eastward,  they  would  both  lead  to  streams,  the 
Soude  and  the  Somme  (not  to  be  confused  with  the  river  Somme 
in  northwestern  France),  flowing  for  some  distance  on  the  low- 
land toward  the  heads  of  the  branches,  but  then  turning  north- 
ward and  entering  the  Marne  directly. 

The  Beheading  of  the  Surmelin  and  the  Petit  Morin.  In  ex- 
planation of  all  these  facts  let  it  be  supposed  that  the  two  pairs, 
Soude-Surmelin  and  Somme-Morin,  were  once  actually  continuous 
streams  at  a  time  before  the  lowland  was  eroded  on  the  weak 
rocks  east  of  the  upland,  and  let  the  verity  of  the  supposition  be 
tested  by  the  likelihood  of  a  natural,  spontaneous  change  from 
that  condition  to  the  present  (cf.  Fig.  91). 

When  the  paired  streams  flowed  westward,  they,  like  the 
Marne,  must  have  run  in  the  direction  of  the  dip  of  the  strata ; 
hence  they  may  all  be  called  consequent  streams.  They  must  all 
have  passed  from  the  weak  Cretaceous  strata  to  the  resistant 
Tertiary  strata.  The  Marne  is  much  the  largest  of  these  three 
streams,  and  its  valley  must  have  been  deepened  rapidly,  while 
the  other  valleys  must  have  been  deepened  slowly.  As  the  valleys 
were  deepened  they  progressively  widened,  but  the  widening  must 
have  been  much  more  rapid  on  the  weak  than  on  the  resistant 
strata  ;  and  the  deep  valley  of  the  Marne  must  have  widened 
in  the  weaker  strata  much  more  rapidly  than  the  neighboring 
shallow  valleys  of  the  Soude-Surmelin  and  the  Somme-Morin. 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     601 

Now  the  question  arises,  Will  the  divides  between  these  three 
valleys  shift  in  such  a  manner  as  to  alter  the  assumed  original 
arrangement  to  the  actual  arrangement  ?  Undoubtedly  they 
would,  and  for  the  following  reasons  : 

The  valley  of  the  Marne  being  deeper  than  that  of  the  Soude- 
Surmelin,  the  divide  between  the  two  would  be  pushed  away 
from  the  larger  and  toward  the  smaller  streams,  and  eventually 
the  upper  course  of  the  Soude-Surmelin  would  be  diverted  by  a 


FIG.  91 

growing  side  branch  of  the  Marne  (the  lower  part  of  the  Soude) 
and  thus  led  to  join  that  vigorous  river,  while  the  lower  course 
of  the  Soude-Surmelin  (the  Surmelin)  would  remain  as  a  dimin- 
ished, beheaded  river.  The  side  branch  of  the  Marne,  which 
causes  the  diversion,  belongs  to  the  class  of  streams  called  sub- 
sequent. Let  us  next  look  at  the  divide  between  the  Soude- 
Surmelin  and  the  Somme-Morin.  At  first,  as  these  streams  are 
of  about  equal  volume,  the  divide  between  them  would  not  be 
pushed  significantly  to  one  side  or  the  other,  but  after  the 


602  PHYSIOGRAPHIC  ESSAYS 

capture  of  the  Soude  by  a  branch  of  the  Marne,  the  Soude  would 
rapidly  deepen  its  valley  on  the  weak  strata,  and  from  that  time 
forward  the  divide  between  the  Soude  and  the  Somme-Morin 
would  be  systematically  pushed  toward  the  latter.  Eventually 
the  upper  waters  of  this  stream  would  also  be  diverted  to  the 
Marne  by  the  way  of  the  lower  Soude,  leaving  the  lower  waters 
(the  Petit  Morin)  as  another  diminished,  beheaded  stream ;  but 
inasmuch  as  this  second  capture  must  occur  at  a  much  later 
date  than  the  first,  it  is  natural  to  expect  that  the  beheaded 
Petit  Morin  will,  at  the  time  of  capture,  have  cut  a  much  deeper 
valley  through  the  upland  than  was  cut  by  the  earlier  beheaded 
stream,  the  Surmelin. 

The  Elbow  of  Capture.  Let  us  call  the  sharp  turn  that  the 
diverted  headwaters  make  where  they  join  the  diverting  stream 
the  elbow  of  capture.  After  the  capture  the  rearranged  water 
course  will  cut  a  sharply  intrenched  valley  above  and  below  this 
elbow,  for  the  diverted  stream,  of  considerable  volume,  being 
turned  into  the  head  of  the  diverting  stream,  where  the  volume 
is  zero,  must  immediately  deepen  its  channel.  As  time  passes, 
the  trench  will  disappear  by  widening,  and  hence  the  occurrence 
of  such  a  trench  may  be  taken  as  an  indication  of  recent  rearrange- 
ment. Similarly,  the  diminished,  beheaded  stream  may  be  more 
or  less  obstructed  by  the  detritus  that  is  washed  into  its  valley 
by  small,  lateral  branches  ;  thus  its  flow  may  be  delayed  by 
swamps,  or  it  may  even  be  held  back  in  shallow  lakes,  as  the  Inn 
is  held  back  in  the  lakes  of  Engadine,  as  described  by  Heim ; 
but  this  is  also  a  relatively  short-lived  condition,  for  as  time 
passes,  the  beheaded  stream  will  adjust  its  grade  to  the  work 
that  its  diminished  volume  has  to  do,  and  its  lakes  and  swamps 
will  disappear. 

In  nearly  all  cases  further  shortening  is  enforced  upon  the 
beheaded  stream  below  the  elbow  of  capture.  It  deepens  its  val- 
ley slowly,  while  the  reenforced  subsequent  diverter  deepens  its 
valley  with  relative  rapidity ;  hence  the  divide  will  be  pushed 
away  from  the  elbow  of  capture,  and  the  beheaded  stream  will 
be  progressively  diminished.  The  distance  of  the  source  of  the 
beheaded  stream  from  the  elbow  of  capture  may  therefore  be 
generally  taken  as  a  measure  of  the  remoteness  of  the  time 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     603 

when  the  capture  took  place.  It  not  infrequently  happens  that 
a  small  stream  is  developed,  flowing  into  the  elbow  of  capture 
from  the  neighborhood  of  the  source  of  the  beheaded  stream, 
and  progressively  lengthening  as  the  divide  is  pushed  away 
and  the  beheaded  stream  is  shortened.  Let  us  call  streams 
of  this  class  inverted  streams.  They  will  manifestly  be  want- 
ing at  elbows  of  recent  capture,  but  they  may  attain  a  length 
of  several  miles  if  the  capture  occurred  long  enough  ago. 


FIG.  92 

Now  look  at  the  actual  arrangement  of  the  streams  on  the 
lowland  west  of  Chalons  and  on  the  upland  beyond  the  escarp- 
ment, while  bearing  these  deductive  criteria  in  mind.  The  Somme 
has  lately  been  captured  by  the  growth  of  a  subsequent  branch 
from  near  the  elbow  of  the  Soude ;  for  behold  at  the  little  vil- 
lage of  Ecury-le-Repos  a  sharp  elbow  in  the  course  of  this  stream 
and  a  narrow  trench  for  a  moderate  distance  above  and  below 
the  elbow.  The  Petit  Morin  is  evidently  the  lower  course  of  the 
Somme.  On  account  of  its  diminished  volume,  it  is  for  the  pres- 
ent unable  to  keep  its  valley  clear  of  the  detritus  that  is  washed 


604  PHYSIOGRAPHIC  ESSAYS 

down  from  the  steep  valley  sides  in  the  upland,  probably  near 
Boissy  and  Le  Thoult ;  hence  the  great  marsh  of  St.  Gond  and 
its  extensive  deposits  of  peat  about  the  head  of  the  stream.  The 
marshy  head  of  the  Petit  Morin  is  still  close  to  the  elbow  of  cap- 
ture at  Ecury-le-Repos,  and  no  obsequent  stream  is  yet  developed 
in  this  case.  The  change  is  clearly  of  recent  date. 

Look  next  at  the  Soude-Surmelin  system.  Here  the  capture 
occurred  long  ago ;  there  is  no  sign  of  a  gorge  at  the  elbow  of 
capture.  An  obsequent  stream,  the  Berle,  about  four  miles  in 
length,  has  grown  toward  the  retreating  escarpment  of  the 
upland,  and  the  head  of  the  beheaded  stream  is  now  ten  miles 
away  from  where  it  stood  at  the  time  when  the  capture  had 
just  taken  place.  Having  lost  its  head  rather  early  in  the 
history  of  the  region,  its  valley  through  the  upland  is  not  cut 
to  a  great  depth ;  it  is  much  shallower  than  the  valley  of  the 
Petit  Morin,  which  was  beheaded  at  a  much  later  period,  when 
it  had  become  nearly  as  deep  as  that  of  the  Marne  itself. 

It  was  while  studying  the  French  maps  at  home  that  I  first 
came  on  this  almost  ideal  example  of  migrating  divides  and 
adjustment  of  streams  to  structures,  but  it  was  not  until  an 
excursion  abroad  in  1894  that  I  was  able  to  study  it  on  the 
ground.  I  then  had  the  gratification  of  confirming  by  direct 
observation,  as  far  as  the  brief  time  at  my  disposal  would  allow, 
the  expectations  formed  from  study  at  a  distance.  The  example 
of  the  Marne  and  its  side  branches  therefore  still  serves  me  as 
a  typical  case  of  adjustments  of  this  kind. 

It  is  curious  to  note  that  another  small  stream,  the  upper 
Vaure,  flows  toward  the  marsh  of  St.  Gond,  but  instead  of 
being  diverted  northward  by  the  Soude  to  the  Marne,  it  is 
diverted  southward  by  the  Superbe,  a  subsequent  branch  of 
the  Aube.  It  seems  also  probable  that  this  subsequent  branch 
has  diverted  the  Maurienne  at  Pleurs,  and  thus  cut  it  off  from 
the  Grand  Morin,  whose  head  is,  like  that  of  the  Surmelin,  on 
the  upland  west  of  the  escarpment. 

It  is  manifest  that  the  terminology  here  employed  will  be  of 
service  in  simplifying  the  description  of  other  examples  of  shift- 
ing divides  and  river  adjustment  if  they  possess  the  same  sys- 
tematic features  as  are  here  so  well  exhibited.  That  such  is  thf 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     605 

case  I  can  confirm  from  the  study  of  several  examples  near 
the  escarpment  of  the  Swabian  Alp  in  Wiirtemberg,  where 
the  headwaters  of  the  Neckar  are  actively  pushing  away  the 
divide  that  separates  them  from  the  northern  tributaries  of 
the  upper  Danube.  Although  the  arrangement  of  parts  is  not 
the  same  as  in  the  example  near  Chalons,  yet  the  homologies 
of  the  two  regions  can  clearly  be  made  out.  The  same  may  be 
said  of  the  rivers  of  central  England,  which  are,  as  a  rule,  well 
adjusted  to  the  valleys  between  the  uplands  of  the  oolite  and 
the  chalk. 

Diversion  of  the  Upper  Moselle  from  the  Meuse.  After  this 
long  digression  let  us  now  return  to  the  case  of  the  Meuse  and 
see  whether  indications  can  be  found  that  any  of  its  branches 
have  been  diverted  to  the  basins  of  the  Seine  or  of  the  Moselle. 
The  first  example  to  be  mentioned  is  found  in  the  neighbor- 
hood of  Toul,  and  for  simplicity  of  description  I  shall  take  the 
liberty  of  changing  the  names  of  the  streams  in  this  region  in 
accordance  with  the  diagram  on  the  following  page,  the  actual 
names  being  given  in  thin-lined  letters,  and  the  assumed  names 
in  heavy-lined  letters.  The  case  may  then  be  briefly  stated  as 
follows :  The  Toul  (upper  Moselle)  once  flowed  through  a  mean- 
dering valley  and  joined  the  Meuse  at  the  little  village  of  Pagny- 
sur-Meuse.  The  meandering  valley  trenches  an  upland  of  middle 
oolite  strata,  but  in  the  course  of  time  the  Pompey,  a  branch  of 
the  Moselle,  pushed  away  the  divide  at  its  head,  tapped  the  Toul 
where  the  city  of  that  name  now  stands,  and  diverted  it  from 
the  Meuse  to  the  Moselle.  My  attention  was  first  called  to 
this  example  by  my  kind  friend,  M.  Emm.  de  Margerie,  who 
was  so  good  as  to  refer  me  to  the  writings  of  several  French 
authors  by  whom  it  had  been  described  more  or  less  fully  and 
to  whose  essays  I  thereupon  referred  either  in  the  original  or 
in  some  citation. 

The  first  fact  to  note  is  that  the  abandoned  valley  between 
Toul  and  Pagny  swings  on  large,  curved  meanders,  after  the 
fashion  often  assumed  by  the  valleys  of  large  rivers,  but  never 
imitated  by  valleys  of  small  streams.  It  is  true  that  the  valleys 
of  small  streams  may,  in  the  course  of  time,  become  compara- 
tively wide,  but  they  can  never  develop  systematically  curving 


6o6 


PHYSIOGRAPHIC  ESSAYS 


meanders  of  large  radius  with  steep,  sloping  bluffs  on  the  out- 
side of  the  curves  and  long,  sloping  spurs  on  the  inside  of  the 

curves.  The  form  of 
the  valley  from  Toul 
to  Pagny,  therefore, 
at  once  suggests  not 
only  that  a  stream 
once  passed  through 
it,  but  also  that  the 
stream  was  a  large 
one. 

In  the  second 
place,  on  looking 
more  closely  at  the 
topographical  details 
in  the  neighborhood 
I  of  Toul,  it  is  seen 

that  we  have  here  a  well-developed  elbow  of  capture,  — a  sharp 

bend  in  the  river  course,  independent  of  local  rock  structure. 

The   Toul    makes   a 

sharp    turn    from    the 

direction  of  its   upper 

course  and  swings  off 

along  the  course  of  the 

Pompey  to  the  Moselle. 

The  Pompey  was  once 

merely    one    of    many 

small  branches  of  the 

Moselle,  of  which  the 

neighboring  Ache  may 

be  taken  as  the  type  ; 

but  in  consequence  of 

adding   the   large   vol- 
ume of  the  Toul  to  the 

formerly  small  volume 

of    the    Pompey,    the 

valley  has  been  distinctly  deepened  both  down  and  up  stream 

from    the   elbow  of    capture    below   the   former  level   of     the 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     607 

streams,  and  now  exhibits  the  steep-sided  trench  characteristic 
of  recent  captures.  Not  only  the  diverted  Toul  but  several  of 
its  branches  above  the  elbow  of  capture  have  intrenched  them- 
selves beneath  the  general  level  of  the  open  valley  plain  of 
lower  oolite  strata  on  which  they  formerly  flowed.  On  restor- 
ing the  surface  of  this  old  valley  floor  by  filling  up  the  trenches 
which  now  dissect  it,  it  may  be  seen  to  slope  at  such  a  grade  as 
would  lead  it  to  the  floor  of  the  meandering  valley  on  the  way 
to  the  Meuse.  Immediately  after  the  diversion  of  the  Toul  we 
may  imagine  that  only  a  small  stream,  the  Pagny,  fed  by 
the  drainage  from  the  valley  slopes,  was  left  to  follow  the 
meandering  valley  to  the  Meuse.  This  would  be  the  diminished, 
beheaded  stream  of  our  terminology.  But  in  consequence  of 
the  development  of  the  deep  trench  at  the  elbow  of  capture 
and  the  accompanying  growth  of  the  reversed  stream,  the 
Ingressin,  the  beheaded  Pagny  has  been  still  farther  short- 
ened and  is  now  not  more  than  two  and  one-half  miles  in  length. 
In  this  connection  the  following  altitudes  are  significant : 

Junction  of  the  Meurthe  and  Moselle  at  Pompey,  about  190  metres. 

Elbow  of  capture,  at  Toul,  204  metres. 

Old  valley  floor  at  elbow  of  capture,  about  255  metres. 

Divide  between  Ingressin  and  Pagny,  265  metres. 

Junction  of  the  Pagny  and  Meuse,  245  metres. 

The  Pagny  and  the  Ingressin.  Let  me  here  turn  a  moment 
from  the  main  subject  to  consider  some  special  features  of  the 
meandering  valley  and  its  present  occupants,  the  Pagny  and 
the  Ingressin.  In  the  first  place,  midway  in  the  valley,  at  the 
village  of  Foug,  there  is  a  little  stream  coming  in  from  the 
Bois  Romont  on  the  north.  The  topographical  details  of  the  dis- 
trict give  good  reason  for  thinking  that  this  little  stream  used 
to  join  the  valley  at  Lay-St.-Remy  on  the  next  meander  to  the 
west,  and  thus  we  have  here  a  repetition  of  an  accident  of  the 
Ste.  Austreberte  type.  When  the  vigorous  Toul  was  running 
through  this  valley  and  widening  its  meander  belt  it  must  have 
pushed  its  swinging  current  so  vigorously  against  the  outer  side 
of  its  curves  that  it  cut  through  the  ridge  separating  the  Foug 
meander  from  the  little  stream  on  the  north,  and  thus  changed 
the  mouth  of  its  own  tributary  from  a  lower  to  an  upper  meander. 


6o8  PHYSIOGRAPHIC  ESSAYS 

This  may  be  added  to  the  evidence  indicating  the  former  passage 
of  a  large  river  through  the  meandering  valley. 

Next  as  to  the  obsequent  Ingressin,  whose  head  is  at  least 
six  miles  from  the  elbow.  The  comparative  narrowness  of  the 
trench  both  above  and  below  the  elbow  of  capture  by  Toul 
would  not  lead  us  to  expect  an  obsequent  stream  of  much 
length,  and  I  therefore  suggest  the  following  explanation  of 
the  rather  surprising  length  of  the  Ingressin.  A  little  south- 
west of  Foug  is  the  narrowest  part  of  the  old  valley,  its  narrow- 
ness here  being  due  to  the  greater  resistance  of  the  middle 
oolite,  which  form  the  highland  through  which  it  is  cut.  From 
these  steep  slopes  it  appears  that  a  significant  amount  of  waste 
has  crept  down  into  the  valley  trough,  obstructing  it  more  or 
less  and  producing  a  swamp  of  small  dimensions.  The  beheaded 
Pagny  seems  to  have  been  unable  to  hold  its  course  through 
this  obstruction.  It  probably  accumulated  for  a  time  in  a  shal- 
low lake  above  the  obstruction  until,  on  overflowing  into  the 
gorge  at  the  elbow,  this  part  of  its  course  reversed  its  direction 
of  flow,  and  thus  gave  rise  to  a  reversed  stream,  which  is  now 
called  the  Ingressin. 

All  this,  however,  only  by  way  of  suggestion.  Further  study 
of  the  geographical  aspects  of  the  country  is  necessary  before 
this  suggestion  deserves  acceptance.  There  need,  however,  be 
no  doubt  on  the  general  problem  concerning  the  diversion  of 
the  Toul  from  the  Meuse  to  the  Moselle,  and  to  my  mind  the 
case  would  be  perfectly  satisfactory  if  no  pebbles  from  the 
Vosges  had  ever  been  found  in  the  valley  of  the  Meuse  below 
Pagny.  The  dimensions  of  the  meandering  valley,  the  system- 
atic form  of  its  bluffs  and  curves,  the  gorge  above  and  below 
the  elbow  of  capture  at  Toul,  the  relation  of  the  old  valley 
plain  in  which  the  gorge  was  cut  to  the  floor  of  the  meander- 
ing valley  that  leads  through  the  upland,  and  the  accident  that 
happened  to  the  little  side  stream  at  Foug,  all  combine  into  so 
systematic  an  arrangement  of  parts  as  to  leave  no  doubt  that 
an  explanation  which  can  account  for  them  by  a  single  and 
simple  process  is  their  true  explanation. 

The  Diminished  Meuse.  Looking  now  again  at  the  Meuse  by 
Commercy  we  must  recognize  it  as  a  river  whose  volume  has 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     609 

been  diminished  by  the  diversion  of  an  important  tributary  to 
another  river  system.  Its  volume  having  diminished,  it  is  unable 
now  to  accommodate  itself  to  the  large  curves  of  its  valley  and 
must,  instead,  advance  in  an  uncertain  course  as  it  staggers 
along  on  the  valley  floor.  Not  only  so ;  having  lost  volume,  it 
seems  unable  to  maintain  so  gentle  a  slope  as  it  had  assumed 
when  its  volume  was  larger,  for  its  flood  plain  now  has  every 
appearance  of  having  filled  up  the  former  valley  trough  to  a 
moderate  depth.  It  therefore  gives  us  an  illustration  of  a  river 
which  has  changed  its  action  from  degrading  its  slope  when  its 
volume  was  large  to  aggrading  its  slope  now  that  its  volume 
is  small. 

What  the  Meuse  has  lost  the  Moselle  has  gained,  and  the 
considerable  addition  that  the  Toul  has  given  to  its  volume 
has  undoubtedly  confirmed  its  habit  of  swinging  boldly  around 
the  meanders  of  its  lower  valley,  even  to  the  point  of  cutting 
almost  or  quite  through  the  necks  of  its  meander  spurs. 

The  Aire  and  the  Bar.  Let  us  next  look  at  the  case  of  the 
Aire.  This  stream  was  once  an  affluent  of  the  Meuse  on  the 
western  side  of  its  basin,  but  it  has  been  diverted  to  swell 
the  volume  of  the  Seine.  The  elbow  of  capture  in  this  case 
lies  about  two  miles  east  of  Grand  Pre.  The  Aire  coming 
from  the  southeast  here  makes  a  sharp  turn  westward  through 
the  ridge  of  lower  Cretaceous  strata  that  bears  the  forest 
of  Argonne  and  thus  joins  the  Aisne.  In  direct  continuation 
of  the  course  of  the  Aire  an  open  valley  leads  to  the  Meuse 
a  little  below  Sedan.  The  greater  length  of  this  valley  is 
followed  by  a  small  stream,  the  Bar ;  but  while  the  valley 
exhibits  strong  meanders  of  rather  large  radius,  the  Bar  is 
nothing  but  a  little  brook  that  wriggles  here  and  there,  back 
and  forth,  on  the  valley  floor.  The  slopes  of  the  valley  floor 
have  the  usual  systematic  arrangement,  —  steeper  slopes  on 
the  outside  of  the  curves,  gentler  slopes  on  the  inside.  A  spur 
that  enters  one  of  the  meanders  from  the  upland  on  the  west, 
covered  by  the  Boisle  Queue  near  St.  Aignan,  has  so  narrow 
a  neck  that  the  canal  leading  from  the  Meuse  to  the  Seine 
system  has  cut  a  trench  through  the  neck  instead  of  going 
around  the  spur.  (See  Fig.  95.) 


6io 


PHYSIOGRAPHIC  ESSAYS 


FIG.  95.  THE  LOWER  VALLEY  OF  THE  BAR 

The  indications  of  the  former  greater  volume  of  water  in  the 
stream  that  once  swung  boldly  around  the  meanders  of  this 
valley  are  perfectly  conclusive.  But  now  the  little  Bar  staggers 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     6ll 


about  in  the  most  random  manner,  quite  unable  to  continue 
the  widening  of  the  meanders  and  the  narrowing  of  the  necks 
of  the  spurs  by  running  systematically  against  the  outer  side 
of  the  valley  curves.  The  meadow-like  quality  of  the  flat  valley 
floor  suggests  that  the  Bar  has  aggraded  its  course  since  the 
greater  volume  of  water  was  withdrawn  at  the  Grand  Pre  elbow, 
thus  repeating  the  features  of  the  Meuse  about  Commercy. 
Following  up  the  Bar,  the  breadth  of  the  valley  and  the  radius 
of  its  large  meanders  are  slowly 
diminished  for  a  long  distance  ;  but 
the  little  Bar,  winding  through  the 
meadow  floor,  rapidly  diminishes, 
and  near  Buzancy  the  meadow  is 
left  without  more  drainage  than 
is  given  by  such  ditches  as  the 
farmers  have  cut  here  and  there 
for  the  better  drying  of  their  flat, 
marshy  fields.  Passing  farther  to 
the  southeast  along  the  meandering 
valley,  we  soon  find  a  small  stream, 
successively  called  the  Moulin,  Bri- 
quenay,  and  Agron,  flowing  south- 
ward for  seven  miles  in  a  trench  cut 
along  the  valley  trough  to  the  elbow 
of  capture  above  Grand  Pre.  This 
is  now  separated  from  the  head  of 
the  Bar  by  a  flat  plain,  and  is  there- 
fore a  reversed  stream,  like  the  Ingressin  already  described. 
Whether  the  divide  at  present  existing  between  the  obsequent 
Briquenay-Agron  and  the  beheaded  Bar  has  been  determined  in 
this  case  by  the  accumulation  of  detritus  washed  in  from  the 
valley  slopes,  as  it  apparently  was  in  the  case  of  the  Pagny,  I 
cannot  surely,  say ;  but  there  does  not  appear  to  be  much  dispar- 
ity between  the  time  required  for  the  amount  of  widening  that 
the  gorge  of  the  Aire  has  received  at  the  elbow  of  capture  and 
for  the  headward  growth  of  the  back-handed  Briquenay-Agron. 
As  in  the  case  of  the  Toul  (upper  Moselle),  so  with  the  Aire ; 
its  old  valley  floor,  occupied  at  a  time  when  it  still  ran  down  the 


FIG.  96 


612  PHYSIOGRAPHIC  ESSAYS 

valley  now  occupied  by  the  Bar,  is  easily  recognized  in  the  flat, 
terrace-like  benches  in  either  direction  from  the  elbow  of  capture  ; 
but  these  benches  now  overlook  the  widened  trench  of  the  di- 
verted Aire  and  the  narrower  trench  of  the  reversed  Briquenay- 
Agron.  A  considerable  depth  is  maintained  by  the  trench  of  the 
Aire  for  some  distance  up  the  stream  from  the  elbow  of  capture 
and,  of  course,  also  through  the  former  valley  floor  of  the  diverter 
on  the  way  to  Aisne ;  but  on  going  up  the  reversed  stream  its 
trench  rapidly  decreases  in  depth,  and  near  Buzancy  it  makes 
but  a  slight  depression  in  the  meadows. 

One  of  the  most  interesting  points  of  view  for  the  appreciation 
of  this  example  of  river  arrangement  is  on  the  flat  fields  of  the 
old  valley  floor  near  the  elbow  of  capture,  just  south  of  the  vil- 
lage of  Champigneulle.  Here  all  the  different  parts  are  easily 
recognized,  as  if  on  a  model  made  expressly  for  the  explanation 
of  the  problem.  In  some  pits  dug  here  and  there  by  the  roadside 
on  the  plain  one  may  see  the  old  river  gravels  laid  down  by  the 
Aire  while  it  was  running  at  this  high  level  on  its  way  northward 
to  the  Meuse.  Another  point  of  view  no  less  instructive  is  offered 
after  surmounting  the  hill  by  which  the  national  road  southward 
from  Sedan,  on  the  Meuse,  crosses  over  to  the  valley  of  the  Bar 
at  Chevenges.  From  the  summit  and  along  the  southward  de- 
scent one  has  a  beautiful  view  of  the  broad  valley  as  it  swings 
around  the  narrow-necked  spur  of  the  Bois  le  Queue,  but  he  looks 
in  vain  for  the  stream  by  which  the  valley  was  cut.  He  fails  to 
see  any  stream  at  all  until  descending  to  the  valley  floor,  when 
the  only  occupant  of  the  great,  boldly  swinging  valley  is  found 
to  be  a  little  meadow  brook. 

Here,  as  before,  it  should  be  remembered  that  it  is  not  the 
width  of  the  valley  that  is  essentially  discordant  with  the  size  of 
the  brook  that  now  drains  it ;  for  in  the  late  maturity  of  the  geo- 
graphical development  of  a  land  surface  even  small  streams  have 
broad  valleys.  The  discordance  which  proclaims  that  the  valley 
is  not  the  work  of  the  existing  stream  is  seen  in  the  relative 
dimensions  of  their  meanders.  The  valley  swings  regularly  in 
curves  of  at  least  half  a  mile  in  radius,  and  maintains  this  habit 
of  curvature  with  small  diminution  far  up  toward  the  elbow  of 
capture  and  probably  still  farther  south.  The  stream  turns  and 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     613 

twists  in  curves  whose  radius  may  often  be  less  than  a  hundred 
feet.    The  following  altitudes  are  instructive  : 

Junction  of  Bar  and  Meuse,  153  metres. 

Divide  in  old  valley  trough  between  the  beheaded  Bar  and  the  reversed 

Briquenay-Agron  on  the  meadows  west  of  Buzancy,  175  metres. 
Junction  of  the  reversed  Briquenay-Agron  with  the  Aire,  at  elbow  of 

capture,  130  metres. 

Floor  of  old  Aire  valley,  at  elbow  of  capture,  182  metres. 
Junction  of  Aire  and  Aisne,  113  metres. 
The  advantage  of  depth  thus  gained  by  the  Aire  is  about  50  metres. 

It  is  worth  noticing  that  if  the  Aire  had  not  been  diverted 
at  Grand  Pre,  it  would  soon  have  been  captured  farther  down 
its  former  valley  at  Brieulles-sur-Bar,  for  here  the  Fournelle,  a 
branch  of  the  Aisne,  has  almost  cut  through  the  forested  ridge 
of  Argonne,  as  the  following  heights  show : 

Mouth  of  Fournelle  in  Aisne  by  Vouziers,  100  metres. 

Divide  between  head  of  Fournelle  and  Bar,  near  Noirval,  174  metres. 

Bar  at  Brieulles,  168  metres. 

In  comparing  the  case  of  the  Toul  (upper  Moselle)  and  Aire, 
we  see  that  these  rivers  are  the  diverted  upper  portions  of 
branches  that  once  belonged  to  the  Meuse.  The  diverters  (by 
which  the  Toul  was  given  over  to  the  Moselle  and  the  Aire  to 
the  Aisne)  may  later  be  called  the  Pompey  and  the  Grand  Pre, 
respectively,  the  latter  ultimately  delivering  its  prize  through  the 
Marne  to  the  Seine.  The  beheaded  streams  of  the  two  are  the 
Pagny  and  the  Bar.  The  former  is  so  insignificant  that  I  have 
had  to  invent  a  name  for  it,  finding  no  name  for  the  stream 
but  only  the  "  Marais  de  Pagny"  entered  on  the  Etat-Major  map 
of  i :  80,000.  The  Bar  is  the  best  example  that  I  have  ever  seen 
of  a  beheaded  stream  trying  ineffectually  to  live  up  to  the  robust 
habits  of  its  great  predecessor. 

The  Diminished  Meuse  again.  The  loss  suffered  by  the  Meuse 
and  the  increase  gained  by  the  Seine  through  the  diversion  of 
the  Aire  are  of  no  great  moment,  but  as  far  as  they  go  they  serve 
to  confirm  each  river  in  the  habits  that  now  characterize  it,.  —  the 
Meuse  in  staggering  with  uncertain  steps  around  its  valley  curves, 
the  Seine  and  the  Moselle  in  swinging  boldly  around  their  curves 


6 14  PHYSIOGRAPHIC  ESSAYS 

and  undermining  the  inclosing  bluffs.  It  should  be  noted,  how- 
ever, that  when  a  large  tributary  is  diverted  from  a  point  high 
up  on  the  trunk  of  a  main  river,  the  loss  of  volume  that  the 
change  produces  may  be  a  large  fraction  of  the  total  volume  that 
once  belonged  to  the  main  river,  and  hence  that  the  loss  may 
greatly  affect  the  ability  of  the  main  river  still  to  follow  the 
swinging  valley  that  it  cut  out  when  its  volume  was  greater.  On 
the  other  hand,  when  a  tributary  of  relatively  small  volume  is 
diverted  from  some  point  near  the  middle  of  the  main  river,  the 
loss  thus  occasioned  will  be  a  comparatively  small  fraction  of  the 
trunk  volume,  and  the  change  of  habit  thus  produced  will  be 
correspondingly  small.  It  is  for  this  reason  that  the  stagger- 
ing of  the  Meuse  near  Commercy  is  so  much  more  marked  than 
between  Sedan  and  Mezieres.  The  loss  of  the  Toul  (upper 
Moselle)  was  a  much  more  serious  affair  for  the  Meuse  than 
the  loss  of  the  Aire. 

Supplementary  Problems.  There  are  certain  aspects  of  this 
problem  that  remain  to  be  considered  briefly.  First,  are  there 
any  other  examples  of  branches  diverted  from  the  system  of  the 
Meuse  to  those  of  its  neighbors  on  the  west  and  east  ?  Although 
I  have  been  unable  to  find  any  direct  signs  of  them  on  the  map, 
there  still  does  seem  to  be  indication  that  other  diversions  have 
occurred.  On  looking  at  the  Meuse  above  Pagny,  it  is  there 
almost  as  much  out  of  proportion  to  its  valley  as  it  is  below 
Pagny.  It  is  possible,  therefore,  that  other  headwater  branches 
higher  up  than  the  upper  Moselle  have  been  diverted.  Looking 
at  the  Aire,  it  appears  that  the  present  radius  of  the  meanders 
is  much  smaller  than  the  radius  of  the  swinging  valley  that  is 
followed  by  the  little  Bar,  and  from  this  it  may  be  inferred  that 
not  only  the  existing  Aire,  but  the  drainage  of  a  still  larger  basin 
once  ran  down  the  valley  of  the  Bar.  Perhaps  the  upper  Ornain 
represents  something  of  the  additional  volume  that  the  Aire  once 
possessed,  but  I  cannot  find  direct  indication  that  such  is  the 
fact.  The  maps  on  the  scale  of  I  :  80,000  seem  hardly  of  suffi- 
cient detail  to  enable  one  to  solve  this  phase  of  the  problem  by 
indoor  study  alone.  The  whole  subject  calls  for  extended  study 
in  the  field,  and  a  more  interesting  problem  could  hardly  be  se- 
lected for  a  summer's  work. 


THE  SEINE,  THE  MEUSE,  AND  THE  MOSELLE     615 

Another  subject  to  which  no  reference  has  yet  been  made  is, 
nevertheless,  of  fundamental  importance  to  the  whole  problem  : 
Why  is  it  that  the  Seine  and  the  Moselle  are  waxing  at  the  ex- 
pense of  the  waning  Meuse  ?  Why  do  they  possess  an  advantage 
while  the  intermediate  stream  is  at  a  disadvantage  ?  How  could 
the  Meuse  ever  have  gained  so  large  a  drainage  area  as  it  once 
must  have  had,  if  at  a  later  state  of  its  history  it  was  to  be  so 
closely  shorn  of  its  branches  ?  This  is  too  large  a  problem  to 
enter  far  upon  now,  but  it  contains  two  elements  that  may  be 
briefly  stated.  One  is  that  many  of  the  streams  in  the  region  of 
the  Meuse  are  longitudinal  streams,  that  is,  they  run  chiefly 
along  the  strike  of  the  weaker  strata  and  their  valleys  have  long 
ascending  slopes  on  the  eastern  side  and  more  abrupt  slopes  on 
the  western  side.  The  highlands  reached  by  these  slopes  are 
determined  by  the  outcrop  of  more  resistant  strata  than  those 
of  the  valleys  which  the  streams  have  excavated.  Longitudinal 
streams  of  this  kind  I  have  called  subsequent,  believing  that 
they  cannot  have  originated  in  immediate  consequence  of  the 
original  slopes  of  the  land  surface  when  it  first  arose  above  the 
sea,  but  that  their  opportunity  came  later  when  the  wasting  of 
the  weak  strata  allowed  the  headward  growth  of  streams  along 
their  strike,  after  the  manner  explained  in  connection  with  the 
adjustments  of  the  Marne  and  its  branches  near  Chalons.  The 
Meuse  and  at  least  some  of  the  branches  that  it  once  had  there- 
fore seem  themselves  to  have  been  the  result  of  depredations 
committed  on  the  territory  of  some  still  earlier  river  or  rivers, 
and  if  this  is  true,  the  sympathy  that  the  present  impoverished 
condition  of  the  Meuse  excites  is  not  deserved. 

However  this  may  be,  why  is  it  that  the  Meuse  has  lately 
found  so  great  difficulty  in  deepening  its  valley  and  thus  saving 
its  branches  from  capture  by  its  neighbors  ?  The  chief  cause  of 
this  difficulty  must  be  looked  for  in  the  uplift  of  the  Ardennes, 
across  whose  resistant  rocks  the  lower  Meuse  has,  during  Terti- 
ary time  (perhaps  only  during  later  Tertiary  time),  been  cutting 
its  grand  gorge.  Like  the  highlands  of  the  middle  Rhine,  the 
Ardennes  consist  of  ancient  and  deformed  rocks  which  have 
once  been  reduced  to  a  peneplain  of  moderate  relief  drained  by 
idle  streams,  but  across  which  the  Meuse  is  now  actively  cutting 


6l6  PHYSIOGRAPHIC  ESSAYS 

a  deep  transverse  valley  in  consequence  of  the  strong  uplift  of 
the  region.  While  the  peneplain  was  yet  a  lowland,  the  Meuse 
was  comparatively  safe  from  depredations,  but  during  the  eleva- 
tion of  the  peneplain  and  thereafter,  great  difficulty  must  have 
been  experienced  in  deepening  the  valley.  The  Moselle  must 
also  have  had  some  difficulty  in  deepening  its  valley  through  the 
uplifted  highlands  of  the  middle  Rhine,  but  the  uplift  there  does 
not  seem  to  have  been  so  great  as  it  was  in  the  Ardennes,  and 
thus  the  Seine  and  the  Moselle  seem  to  have  gained  an  advan- 
tage over  the  unlucky  river  between  their  headwaters.  It  is, 
indeed,  remarkable  enough  that  the  Meuse  is  still  able  to  main- 
tain its  course  across  the  uplifted  Ardennes,  and  its  success  can 
only  be  explained  by  regarding  it  as  an  excellent  example  of  an 
antecedent  river.  It  has  battled  manfully  to  preserve  its  course, 
and  in  this  it  has  been  wonderfully  successful,  for  the  highlands 
of  the  Ardennes  through  which  its  deep  gorge  is  cut,  are  now 
higher  than  the  uplands  in  which  its  meandering  valley  is  sunk 
for  some  distance  above  the  Mezieres.  Yet  although  successful 
in  holding  its  way  through  the  revived  mountains  of  the  Ardennes, 
it  has  had  to  pay  dearly  for  this  success  by  the  loss  of  its  side 
branches.  The  hard  rocks  of  the  uplifted  Ardennes  form  a  sill 
that  holds  the  upper  Meuse  at  a  relatively  high  level  and  allows 
the  head  branches  of  the  Seine  and  Moselle  to  under-cut  it  on 
either  side.  Thus  it  is  left  as  a  waning  river,  still  persevering 
bravely  in  its  course,  but  much  embarrassed  by  the  diversion  to 
its  encroaching  neighbors  of  certain  tributaries  from  whom  it 
had  expected  loyal  assistance  in  its  great  task  of  cutting  a  way 
through  all  obstacles  to  the  sea. 


XXIII 

THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS 

The  Present  Condition  of  the  Problem  of  Glacial  Erosion.  The 
problem  of  glacial  erosion  in  mountains  has  in  recent  years  been 
carried  many  steps  towards  its  solution  by  means  of  a  series  of 
studies  in  which  the  forms  of  formerly  glaciated  and  of  never 
glaciated  mountains  have  been  systematically  compared.  It  has 
thus  come  to  be  believed  by  a  number  of  observers  that  the 
glacial  erosion  of  piedmont  lake  basins  must  be  extended  to  the 
over-deepening  of  the  main  mountain  valleys  far  upstream  from 
the  lakes,  and  that  the  retrogressive  glacial  erosion  of  cirques 
carries  with  it  the  sapping  and  sharpening  of  the  culminating 
ridges  and  peaks.  The  last-named  effect  is  truly  not  the  direct 
work  of  ice,  but  it  is  so  closely  dependent  upon  glacial  erosion 
that  it  should  be  included  in  any  discussion  of  the  sculpture  of 
mountains  by  glacial  agencies,  just  as  the  wearing  of  slopes  and 
ridges  by  the  weather  goes  with  the  erosion  of  valley  bottoms 
by  rivers. 

The  observations  and  discussions  that  have  led  to  a  belief  in 
strong  glacial  erosion  are  to  be  found  in  many  different  essays. 
Some  of  the  earlier  essays  were,  based  on  almost  intuitive  in- 
sight ;  as  when  Ramsay  was  led  to  advocate  the  glacial  erosion 
of  lake  basins,  Gastaldi  to  accept  the  glacial  erosion  of  cirques, 
and  Helland  to  announce  the  glacial  erosion  of  fiords.  Many  of 
the  later  essays  are  more  surely  founded  on  comparative  studies, 
such  as  those  on  over-deepened  valleys  in  the  Cascade  mountains 
of  Washington  by  Gannett,  and  in  the  Alps  by  Penck ;  on  the 
fiords  of  Alaska  by  Gilbert,  and  of  New  Zealand  by  Andrews ; 
on  the  cirques  of  the  Sierra  Nevada  of  California  by  Johnson, 
of  the  Carpathians  by  de  Martonne,  and  of  the  Big  Horns  by 
Matthes ;  and  of  the  sharpened  peaks  of  the  Alps  by  Richter, 
and  of  Skye  by  Harker.  There  has  thus  been  a  great  growth  in 
the  number  of  facts  to  be  explained  and  a  notable  advance  in  the 

617 


618  PHYSIOGRAPHIC  ESSAYS 

methods  by  which  explanation  is  reached.  It  seems  no  exagger- 
ation to  say,  in  view  of  all  this  progress,  that  the  sculpture  of 
mountains  by  glaciers  has  been  given  that  degree  of  extreme 
probability  which  we  may  fairly  call  demonstration.  It  should 
not,  however,  be  overlooked  that  certain  investigators  still  re- 
main unconvinced,  notably  Heim  and  Kilian  in  the  Alps,  Bon- 
ney  and  Garwood  in  England,  and  Spencer  and  Fairchild  in  the 
United  States. 

Method  of  Discussion  here  Adopted.  Most  of  those  above, 
named  as  believing  in  strong  glacial  erosion  have  not  been  led 
to  their  belief  by  an  intimate  study  of  the  physics  of  glaciers  or 
of  the  mechanics  of  glacial  erosion,  but  by  a  study  of  the  unlike 
forms  that  characterize  glaciated  and  non-glaciated  mountains, 
as  has  already  been  stated.  Their  line  of  thought  seems  to  be 
essentially  as  follows :  "  It  is  difficult  to  determine  whether  the 
ancient  glaciers  did  or  did  not  significantly  modify  the  mountains 
that  they  occupied,  as  long  as  we  study  only. the  structure  and 
movement  of  existing  glaciers.  Let  us  therefore  adopt  another 
method.  We  will  make  two  contrasted  suppositions  :  glaciers 
cannot  erode,  and  glaciers  can  erode  ;  we  will  consider  the  appro- 
priate consequences  of  each  supposition  separately  ;  we  will  next 
confront  these  consequences  with  the  facts  of  observation ;  and 
then,  according  as  one  or  the  other  group  of  consequences  is 
verified  by  the  facts,  we  shall  be  able  to  determine  impartially 
which  one  of  the  suppositions  is  correct." 

In  such  a  problem  as  this  if  is  evident  that  if  glaciers  cannot 
erode,  we  ought  not  to  find  any  significant  differences  between  the 
forms  of  glaciated  and  of  non-glaciated  mountains  ;  but  if  glaciers 
can  erode,  we  ought  to  find  in  glaciated  mountains  a  whole  series 
of  peculiar  forms,  and  these  forms  ought  to  be  appropriately  re- 
lated to  the  form  and  movement  of  glaciers.  The  essential  steps 
in  the  application  of  this  method  may  now  be  outlined. 

The  Forms  of  Normally  Sculptured  Mountains.  The  forms  of 
non-glaciated,  normally  sculptured  mountains  are  well  known  to 
exemplify  Playf air's  law  as  to  the  accordant  junction  of  lateral 
and  main  streams  and  valleys.  In  mountains  which  have  reached 
a  sub-mature  or  a  mature  stage  of  normal  carving,  and  in  which 
lakes  are  therefore  drained  away  and  waterfalls  are  worn  down 


THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS     619 

to  grade,  except  in  small  headwater  streams,  the  law  of  decreas- 
ing slope  from  stream  head  to  stream  mouth  will  also  obtain ; 
and  then  the  accordance  that  has  been  earlier  developed  at  the 
junctions  of  main  and  side  streams  will  be  found  to  prevail  even 
at  the  junctions  of  the  innumerable  headwater  branches  into 
which  river  systems  are  divided  ;  and  as  each  little  head  stream 
is  followed  up  to  its  source,  its  steepening  slope  will  be  prolonged 
up  the  still  steeper  waste-covered  slopes  in  the  head  and  sides  of 
the  ravines  which  ascend  to  the  mountain  crests  ;  but  over  the 
crests  themselves  there  will  be  a  decreasing  convex  slope.  Ex- 
amples of  these  normal  forms  which  have  come  under  my  own 
observation  are  parts  of  the  Apennines  in  northern  Italy,  the 
Cevennes  in  southeastern  France,  the  Black  mountains  of  North 
Carolina,  some  of  the  lower  ranges  in  the  Rocky  mountains  and 
farther  west,  and  certain  non-glaciated  members  of  the  Tian  Shan 
system  ;  to  these  might  be  added  the  outer  ranges  of  the  Hima- 
layas at  Simla  and  certain  ranges  in  the  Argentine  Republic, 
except  that,  when  these  examples  were  seen,  my  attention  had 
not  been  especially  awakened  to  the  points  here  considered.  The 
perfection  of  stream  organization  thus  exhibited,  with  its  deli- 
cate interdependence  of  parts,  should  be  regarded  as  one  of  the 
'strongest  witnesses  to  the  truth  of  the  principles  of  rational 
uniformitarianism. 

An  important  extension  of  Playfair's  law  concerns  the  relation 
of  stream  channels  to  each  other  and  to  the  valleys  in  whose 
floors  they  are  eroded.  The  channels  occupy  a  very  small  part 
of  the  cross  section  of  the  valleys,  because  water  is  a  nimble  fluid 
and  its  streams  flow  quickly  in  comparatively  slender  courses  ; 
furthermore,  the  very  fact  that  the  stream  surfaces  and  the  val- 
ley floors  that  border  them  meet  in  accordant  level  at  the  points 
of  stream  and  valley  junction  necessitates  the  discordant  junc- 
tion of  the  channel  beds  whenever  the  confluent  streams  are  of 
different  size.  The  discordant  junction  of  channel  beds  is  not  a 
conspicuous  fact,  because  the  streams  in  the  comfortable  cli- 
mates of  the  older  civilized  countries  usually  fill  their  channels 
and  hide  their  beds  from  immediate  observation ;  but  it  is,  never- 
theless, a  well-assured  fact  and  a  very  important  element  in  the 
present  discussion. 


620  PHYSIOGRAPHIC  ESSAYS 

Deductions  from  Theories.  Now  if  glaciers  have  no  erosive 
power,  then  maturely  dissected  mountains  that  have  been  glaci- 
ated should  present  no  features  significantly  unlike  those  above 
described  for  mature  non-glaciated  mountains.  But  if  glaciers 
have  strong  erosive  power,  special  and  significant  features  should 
be  found  in  mountains  where  glaciers  have  had  time  enough  to 
do  their  work.  The  most  notable  features  of  this  kind  that  one 
would  expect  to  find,  may  be  stated  as  follows :  A  large  part  of 
the  cross  section  of  a  glaciated  valley  would  be  included  in  the 
trough-like  channel  that  was  scoured  out  and  occupied  by  the 
heavy,  sluggish  glacier  ;  the  bed  of  such  a  trough  would  have 
rock  steps  and  rock  basins  similar  to  those  in  the  bed  of  a  river 
channel,  but  appropriately  of  much  greater  size ;  the  sides  or 
walls  of  such  a  trough  would  be  comparatively  even  and  parallel, 
like  the  sides  or  banks  of  a  river  channel ;  the  troughs  of  small 
side  glaciers  would  necessarily  be  of  much  less  depth  than  the 
troughs  of  large  trunk  glaciers,  and  hence  the  bed  of  a  side 
trough  would  hang  hundreds  of  feet  over  the  bed  of  the  trunk 
trough ;  the  valley  sides  above  the  trough  would,  in  mountains 
of  mature  sculpture,  be  less  steep  than  the  trough  walls  them- 
selves ;  the  heads  of  the  glacial  beds  would  be  broad-floored 
cirques,  because  the  heads  of  glaciers  are  broad  and  leaf-like 
instead  of  being  divided  minutely  like  the  headwater  streams  of 
rivers ;  the  summits  and  ridges  between  cirques  which  head  near 
each  other  would  be  sharpened  into  peaks  and  aretes  by  atmos- 
pheric weathering,  induced  by  the  retrogressive  glacial  erosion 
of  the  ice  in  the  cirques,  and  by  the  glacial  widening  of  the 
troughs.  Other  features  might  be  named,  appropriate  to  glaciers 
of  large  or  small  size,  or  of  short  or  long  duration,  but  those 
here  set  forth  are  sufficient  for  a  brief  exposition. 

Graphic  Illustrations  of  Glacial  Sculpture.  The  attempt  is 
made  in  Figs.  97,  98,  and  99  to  present  examples  of  the  unlike 
features  just  described.  The  figures  make  no  pretense  of  being 
drawn  from  actual  mountains ;  but  they  are  in  a  way  made  up 
from  various  observations,  sketches,  and  photographs,  and  in 
this  respect  correspond  to  the  "deduced  consequences"  of  the 
hypothesis  that  glaciers  can  erode,  as  announced  in  the  preced- 
ing paragraph  ;  for  the  consequences  are  not  simply  abstract 


THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS     621 


deductions;  they  have  been  tested  at  nearly  every  step  by  obser- 
vation. The  figures  undoubtedly  need  many  amendments;  they 
are  hard  and  crude,  yet  they  have  some  value  in  making  the 
preceding  paragraph  clearer  than  it  would  be  without  them. 
Moreover,  the  figures  ambitiously  attempt  to  exhibit  the  changes 
that  a  given  mountain  mass  would  suffer  from  a  pre-glacial  time 
of  normal  sculpture,  through  a  pronounced  glacial  period,  to  a 
post-glacial  time  in  which  the  work  of  the  glacial  period  has  as 


FIG.  97.    A  NORMALLY  ERODED  MOUNTAIN  MASS,  NOT  AFFECTED  BY 
GLACIAL  EROSION 

yet  been  but  little  affected  by  the  return  of  normal  conditions ; 
in  this  respect  they  are  necessarily  only  ideal  examples. 

Fig.  97  shows  the  rounded,  dome-like  forms  of  a  subdued  moun- 
tain mass.  The  cliffs  and  ledges  of  an  earlier  stage  of  normal 
erosion  have  been  worn  away,  and  the  waste  cover  has  been 
very  generally  extended  over  the  graded  slopes  that  now  reach 
from  valley  bottom  to  mountain  top.  This  stage  of  mountain 
sculpture  was  chosen  because  it  is  so  well  represented  in  the 
Sawatch  range  of  the  Rocky  mountains  in  Colorado  in  associa- 
tion with  glacially  sculptured  forms,  such  as  are  illustrated  in 


622  PHYSIOGRAPHIC  ESSAYS 

the  later  figures.  Normally  sculptured  mountains  of  sharper 
form,  like  those  of  southern  California,  might  have  been  taken, 
had  I  seen  them  otherwise  than  in  photographs.  The  main  val- 
ley is  widely  opened  ;  its  floor  is  well  graded  to  a  continuous 
slope ;  its  stream  has  no  lakes  or  falls,  but  swings  smoothly 
along  a  somewhat  sinuous  course  between  the  spurs  that  come 
down  with  moderate  slope  from  the  higher  ridges.  The  side 
valleys  branch  in  a  delicate  fashion  upwards,  splitting  the  spurs 
into  many  spurlets ;  but  all  the  streams  and  valley  floors  unite 
in  accordant  fashion  at  their  many  points  of  junction.  The 
spurs  are  round-shouldered  forms,  exhibiting  very  few  outlines 
by  which  their  elusive  curves  may  be  represented  ;  indeed,  as 
here  drawn,  they  have  an  undue  resemblance  to  the  sprawling 
feet  of  some  huge  pachyderm.  I  believe  that  if  mountains  of 
this  kind  had  been  more  familiar  to  those  who  have  discussed 
the  question  of  glacial  sculpture  in  the  Alps,  a  closer  approach 
to  agreement  on  the  question  of  glacial  erosion  might  have 
been  reached  ere  now. 

Fig.  98  is  intended  to  represent  the  accomplished  work  of  a 
heavy  glacial  system  on  the  mountain  mass  of  Fig.  97.  The 
main  glacier  has  gained  room  for  its  broad  current  by  wearing 
off  the  ends  of  the  spurs  that  formerly  entered  the  main  valley 
from  either  side ;  and  it' has  gained  room  for  its  heavy  and  deep 
ice  body  by  excavating  the  valley  floor  to  a  greater  depth  than 
it  had  in  pre-glacial  time.  The  side  glacier  which  enters  from 
the  upper  left  corner  of  the  figure  is  manifestly  less  deep  than 
the  main  glacier ;  hence,  while  the  ice  surfaces  of  the  main 
and  side  ice  streams  unite  at  accordant  grade,  the  beds  of  their 
troughs  or  channels  cannot  unite  in  that  even  fashion ;  for  when 
the  troughs  are  once  scoured  out  to  a  satisfactory  depth  for  the 
two  unequal  ice  streams,  further  change  of  trough  depth  will 
be  small.  The  smaller  branch  glaciers  in  the  main  mountain 
mass  have  enlarged  the  branch  valleys  that  they  occupy,  and 
retrogressive  erosion  at  the  heads  of  these  glaciers  has  trans- 
formed the  tapering  valley  heads  of  pre-glacial  time  into  blunt- 
headed  cirques.  The  slopes  of  the  spurs  and  summits  have  been 
greatly  steepened,  and  the  ridges  and  peaks  greatly  sharpened, 
by  the  active  weathering  resulting  from  glacial  under-cutting  in 


THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS     623 

the  branch  troughs  and  cirques.  On  the  extreme  right  another 
mountain  is  shown  in  which  two  cirques  have  been  excavated, 
not  of  sufficient  size  to  transform  the  pre-glacial  dome  into  a 
sharpened  peak,  yet  large  enough  to  have  encroached  on  the 
spur  that  separated  them,  and  thus  to  have  transformed  part  of 
it  into  a  serrate  ridge.  Mt.  Elbert,  the  highest  summit  of  the 
Rocky  mountains  within  the  United  States,  presents  just  this 
sort  of  a  contrast  to  its  slightly  lower  neighbor,  La  Plata  peak, 
whose  summit  has  been  sharpened  into  Alpine  form.  If  the  gla- 
cial conditions  here  pictured  should  last  long  enough,  it  is  not  to 
be  doubted  that  the  mountains  would  in  time  be  reduced  to 
lower  and  gentler  forms  than  are  here  presented  in  the  toothed 
peaks  and  serrated  spurs  of  the  central  mass  ;  and  eventually 
they  might  be  worn  down  so  low  that  the  glaciers  would  slowly 
and  spontaneously  disappear,  in  consequence  of  the  increasing 
mildness  of  climate  thus  produced,  —  such  being  Tyndall's  sug- 
gestion for  the  Alps  ;  but  the  very  fact  that  strongly  glaciated 
forms,  with  the  associated  peaks  and  aretes,  now  characterize  the 
ranges  that  were  heavily  glaciated  in  Pleistocene  time,  suffices 
to  prove  that  the  glaciers  did  not  disappear  because  of  their' 
own  action  in  wearing  down  the  mountains,  but  because  of  some 
external  control  of  climatic  change. 

Fig.  99  illustrates  the  appearance  of  the  mountains  and  valleys 
after  the  glaciers  of  Fig.  98  have  melted  away.  Now  there  is  a 
superabundance  of  detail ;  the  difficulty  in  drawing  is  to  select 
the  most  significant  outlines  and  to  omit  the  rest.  The  forms 
that  rose  above  the  ice  streams  in  Fig.  98  are  here  reproduced, 
without  essential  change.  The  spurs  on  the  left  are  unaltered 
in  form,  but  are  somewhat  worn  down  from  their  appearance 
in  Fig.  97.  The  forms  that  were  buried  under  the  ice  streams 
of  Fig.  98  are  here  disclosed  to  the  light  of  day.  The  troughs  of 
the  smaller  branch  glaciers  have  ungraded  floors,  on  which  rock 
basins  and  rock  steps  alternate.  The  troughs  of  the  large  side 
glacier  and  of  the  main  glacier  are  better  smoothed.  Alluvial 
fans  are  already  accumulating  on  their  sides,  just  as  they  are 
in  the  Alps  and  in  other  glaciated  ranges.  The  fact  of  such 
accumulation  suffices  to  prove  a  strong  change  from  the  condi- 
tions under  which  the  troughs  were  excavated  to  the  conditions 


624 


PHYSIOGRAPHIC  ESSAYS 


in  which  they  are  now  being  filled  up.  The  truncated  spur  ends 
now  continue  downwards  in  the  over-steepened  trough  sides  and 
curve  at  the  base  into  the  U-shaped  trough  floor.  The  junctions 
of  the  various  glacial  troughs,  to  which  the  name  of  valleys  is 
of  course  ordinarily  applied,  are  essentially  discordant.  The 
trough  of  the  large  side  glacier  hangs  high  above  the  floor  of 
the  main  glacier  trough ;  the  troughs  of  the  smaller  branch  gla- 
ciers hang  over  the  trough  of  the  large  side  glacier.  If  the  main 


FIG.  98.   THE  SAME  MOUNTAIN  MASS  AS  IN  FIG.  97,  STRONGLY  AFFECTED 
BY  GLACIERS  WHICH  STILL  OCCUPY  ITS  VALLEYS 

trough  could  be  followed  down  to  its  end,  a  large  basin  should 
be  shown,  occupied  by  a  lake,  and  inclosed  by  morainic  walls. 
As  time  progresses,  all  these  peculiar  features  will  be  changed 
to  normal  features.  A  beginning  of  such  changes  is  seen  in  the 
little  slits  by  which  the  mouths  of  the  hanging  valleys  are  already 
beginning  to  be  cut  down  ;  in  the  filling  of  the  lakelets  in  the 
rock  basins  of  the  smaller  branch  troughs  ;  and  in  the  rapid 
wasting  of  the  sharpened  ridges  and  peaks,  by  which  they  will 
in  time  be  rounded  again  ;  but  the  small  amount  of  work  thus 


THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS     625 

far  accomplished  proves  that  the  time  since  the  evacuation  of 
the  district  by  its  glaciers  is  comparatively  short. 

It  is  manifest  that  if  a  vigorous  glacial  system  should  soon 
again  come  to  occupy  the  mountainous  area  of  Fig.  99,  it  would 
produce  relatively  small  changes  compared  to  those  by  which 
the  forms  of  Fig.  97  have  been  altered  to  those  of  Figs.  98  and 
99  ;  for  the  glacier  system  of  the  second  epoch  would  find  the 
valley  troughs  so  well  adapted  to  its  needs  that  there  would  be 


FIG.  99.   THE  SAME  MOUNTAIN  MASS  AS  IN  FIG.  98,  SHORTLY  AFTER  THE 
GLACIERS  HAVE  MELTED  FROM  ITS  VALLEYS 

relatively  small  necessity  of  modifying  them.  The  amount  of 
sculpture  effected  in  a  first  glacial  epoch  may  therefore  be 
reasonably  estimated  as  of  much  greater  volume  than  in  a 
second  glacial  epoch. 

Consequences  of  Theories  confronted  with  Facts.  When  glaci- 
ated mountains  are  visited  with  the  unlike  consequences  of  the 
contrasted  supposition  above  stated  in  mind,  there  can  be  little 
doubt  whether  glaciers  are  effective  eroding  agents  or  not.  As 
far  as  the  glaciated  mountains  of  the  world  have  been  explored, 


626  PHYSIOGRAPHIC  ESSAYS 

it  is  found  that  they  possess  a  large  number  of  peculiar  forms, 
which  differ  most  strikingly  from  the  forms  due  to  the  normal 
processes  of  erosion  ;  it  is  further  found  that  these  peculiar 
forms  are  distributed  with  respect  to  one  another  in  a  most  sys- 
tematic and  significant  manner  ;  and  it  is  finally  perceived  that 
the  peculiar  forms  are  essentially  similar  to  those  above  described 
and  figured  as  producible  by  glaciers,  under  the  supposition  that 
glaciers  have  effective  erosive  power  and  that  they  have  had 
time  to  use  it.  Thus  the  efficiency  of  glaciers  in  carving  glaci- 
ated mountains  is  demonstrated  by  essentially  the  same  method 
that  has  so  thoroughly  demonstrated  the  efficiency  of  the  normal 
erosive  agencies  in  carving  non-glaciated  mountains. 

It  can  hardly  be  questioned  that  if,  as  Andrews  has  well  pointed 
out,  students  of  mountains  had  not  come  upon  glaciated  forms 
until  after  they  had  seen  a  good  variety  of  normal  forms,  the  ex- 
ceptional quality  of  the  needle  peaks  and  the  serrated  ridges,  of 
the  rock  basins  and  the  rock  steps,  of  the  truncated  spur  ends 
and  the  over-steepened  trough  walls,  of  the  hanging  side  val- 
leys and  the  over-deepened  main  valleys,  would  have  been  sooner 
appreciated.  But,  as  a  matter  of  fact,  the  Alps  and  other  strongly 
glaciated  ranges  have  been  taken  as  types  of  mountain  form  from 
a  time  when  there  was  no  question  at  all  of  glacial  erosion  ;  and 
as  a  consequence  the  exceptional  quality  of  many  Alpine  forms 
has  passed  relatively  unnoticed.  The  literature  of  the  subject 
shows  that  the  peculiar  features  which  characterize  glaciated 
mountains  are  not  regarded  as  exceptional  by  observers  whose 
experience  has  been  gained  chiefly  in  mountains  like  the  Alps ; 
yet,  on  the  other  hand,  the  peculiar  features  of  glaciated  moun- 
tains are  very  impressive  when  they  are  seen  by  one  whose  .stand- 
ard of  normal  mountain  form  has  been  established  in  non-glaciated 
mountains,  and  still  more  so  when  they  are  considered  in  view  of 
the  reasonable  consequences  of  the  supposition  that  glaciers  can 
erode  their  valleys  or  can  modify  preexistent  normal  valleys. 

Examples  of  glaciated  mountains  known  to  me  from  my  own 
experience  to  possess  the  peculiar  features  above  mentioned  are : 
the  Highlands  of  Scotland,  where  hanging  cirques  (corries), 
trough  valleys,  and  valley-floor  lakes  abound  ;  the  Alps,  where 
all  of  the  characteristic  forms  of  glaciated  mountains  are  strongly 


THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS     627 

developed  ;  Norway,  where  the  relation  of  hanging  lateral  valleys 
and  over-deepened  main  valleys  is  persistent  and  convincing; 
various  ranges  of  the  Rocky  mountains  in  the  United  States, 
where  the  contrast  of  glaciated  and  non-glaciated  forms  is  very 
striking ;  and  some  of  the  higher  ranges  in  the  Tian  Shan.  In 
several  of  these  ranges  the  sharpness  of  the  peaks  and  aretes 
between  neighboring  cirques  is  in  strong  contrast  to  the  more 
rounded  summits  where  cirques  are  farther  apart  or  absent. 
When  we  note  the  significant  variation  in  the  size  of  these  gla- 
cial features  from  the  isolated  small  cirques,  such  as  Partsch  has 
described  in  the  low  mountains  of  central  Germany,  to  the  great 
confluent  cirques  and  deep  trough  valleys  of  the  high  Sierra 
Nevada,  as  described  by  Lawson ;  when  we  recall  their  world- 
wide distribution,  from  the  great  fiord  systems  of  Alaska,  as  set 
forth  by  Gilbert,  to  the  only  less  impressive  fiords  of  New  Zealand, 
as  pictured  by  Andrews  ;  and  when  we  note  the  systematic  rela- 
tions of  their  several  elements,  as  has  been  so  fully  presented  for 
the  various  glacial  systems  of  the  Alps  in  the  masterful  mono- 
graph by  Penck  and  Bruckner,  now  approaching  completion,  the 
trustworthiness  of  these  unanimous  witnesses  to  glacial  erosion 
is  unimpeachable.  It  should  not,  however,  be  forgotten  that  gla- 
ciated mountains  present  certain  smaller  elements  of  form  for 
which  no  satisfactory  explanation  has  yet  been  offered  ;  it  is 
because  these  elements  are  truly  subordinate  to  the  prevailing 
larger  features  that  they  are  not  given  consideration  here.  It 
must  also  not  be  overlooked  that  the  actual  processes  of  glacial 
erosion  are  not  yet  fully  understood ;  as  to  this  important  prob- 
lem it  will  only  be  noted  that  while  the  plucking  of  large  blocks 
must  .be  important  as  long  as  the  glacial  bed  is  uneven,  the 
scouring  of  ledges  and  the  grinding  of  plucked  blocks  to  fine 
waste  must  also  be  allowed  great  measure  of  effectiveness,  be- 
cause the  coarse-textured  moraines  at  the  lower  end  of  glaciated 
valleys  are  generally  so  small  in  comparison  to  the  excavated 
spaces  farther  upstream. 

Insufficiency  of  Arguments  against  Glacial  Erosion.  A  brief 
consideration  may  be  given  as  to  the  insufficiency  of  certain 
arguments  advanced  by  those  who  do  not  believe  that  glaciers 
have  any  significant  power  to  erode  valleys. 


628  PHYSIOGRAPHIC  ESSAYS 

It  has  been  noted  that  the  ice  at  the  side  or  the  lower  end  of 
glaciers,  where  its  movement  against  the  adjoining  rock  is  open 
to  observation,  will  flow  around  a  ledge  instead  of  removing  it. 
The  same  may  be  said  of  water ;  yet  no  one  doubts  that  water, 
armed  with  rock  waste,  is  an  effective  agent  of  erosion.  It  seems 
as  if  the  essential  element  of  abundant  time  were  here  neglected 
by  the  non-glacial  erosionists  ;  for  even  if  we  accept  the  epigram 
that  glaciers  are  to  mountains  what  sandpaper  is  to  furniture,  it 
cannot  be  doubted  that  sandpaper  would  wear  any  piece  of  furni- 
ture down  to  nothing  if  it  were  used  long  enough  and  if  the 
supply  of  cutting  sand  were  continually  renewed.  And  it  must 
be  remembered  that  we  cannot  measure  the  duration  of  the  sev- 
eral epochs  of  the  glacial  period  in  various  mountain  ranges  until 
we  know  the  rate  and  the  amount  of  glacial  work.  At  present 
both  these  quantities  are  more  or  less  uncertain  ;  it  is  therefore 
premature  at  present  to  conclude  that  glaciers  cannot  have  done 
much  work  because  they  seem  to  work  slowly. 

It  has  been  urged  that  once  the  loose  material  of  pre-glacial 
weathering  is  scoured  away,  deeper  glacial  erosion  is  insignificant. 
This  not  only  overlooks  the  possible  long  duration  of  a  glacial 
epoch,  whereby  work  of  slow  rate  can  reach  a  great  amount ;  it 
also  begs  the  whole  question  of  the  method  of  glacial  erosion. 
There  is  much  evidence  from  the  detailed  form  of  the  cliffs  and 
sills  in  glacial  troughs  that  the  plucking  of  joint  blocks  as  well 
as  the  scouring  of  rock  surfaces  plays  a  large  part  in  glacial  ero- 
sion, and  that  this  process  goes  on  without  any  aid  from  weath- 
ering in  the  ordinary  sense ;  that  plucking  may  exceed  scouring 
in  the  earlier  stages  of  the  modification  of  normal  valleys  to  gla- 
cial troughs,  if,  indeed,  it  is  not  still  an  important  process  even 
after  the  troughs  have  been  worn  fairly  round  and  smooth.  In 
the  absence  of  all  opportunity  for  direct  observation  of  this 
process  beneath  the  trunk  of  a  heavy  glacier,  it  may  be  better 
determined  by  a  comparison  of  the  forms  of  once-glaciated  and 
never-glaciated  mountains  than  in  any  other  way. 

It  is  often  pointed  out  that  the  lower  end  of  a  glacier  advances 
over  loose  deposits  without  removing  them ;  and  to  this  may  be 
added  the  unquestionable  fact  that  broad  and  heavy  sheets  of  till 
in  the  glaciated  areas  of  Europe  and  North  America  lie  upon 


THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS    629 

unconsolidated  gravels.  To  infer  from  these  facts  that  glaciers 
cannot  greatly  erode  their  channels  would  be  equivalent  to  in- 
ferring that  a  stream  which  descends  from  a  mountain  into  a 
desert  and  lays  down  its  detritus  at  its  withering  lower  end  can- 
not erode  the  valley  through  which  its  upper  course  descends ; 
or  equivalent  to  inferring  that  the  Ganges,  which  is  spreading 
out  a  great  delta  among  the  distributaries  near  its  mouth,  cannot 
erode  deep  valleys  in  the  mountains  of  its  source.  This  argument 
cannot  be  accepted  as  valid  until  it  is  shown  that  the  action  of 
the  small  and  vanishing  lower  end  of  a  glacier  may  be  fairly 
taken  to  represent  the  action  of  its  heavy  middle  part.  The  con- 
trasts between  the  bare  rock  surfaces  of  the  Scandinavian  or  the 
Laurentian  highland  and  the  heavy  drift  deposits  on  the  plains 
of  northern  Germany  or  the  prairies  of  the  upper  Mississippi 
valley  suffice  to  prove  that  glacial  action,  like  river  action,  varies 
from  place  to  place  ;  in  both,  erosion  characterizes  the  upper  and 
middle  parts,  and  deposition  characterizes  the  lower  part.  The 
glacial  sculpture  of  mountains,  as  here  set  forth,  is  not  in  the 
least  inconsistent  with  the  glacial  deposition  of  mountain  waste 
on  the  piedmont  lowlands. 

It  is  sometimes  said  that  rocky  knobs,  rising  like  those  of 
Sion  from  a  valley  floor,  and  showing  rough  ledges  on  their 
down-valley  side,  contradict  the  idea  of  glacial  erosion  ;  for  it  is 
urged  that  if  glaciers  erode,  such  knobs  ought  to  be  worn  away. 
There  are  several  unproved  tacit  postulates  in  this  argument. 
It  is  silently  assumed  that  the  knobs  in  question  retain  approxi- 
mately their  pre-glacial  form ;  but  it  may  well  be  that  they  are 
unconsumed  remnants  of  greatly  eroded  masses,  and  the  choice 
between  these  alternatives  is  precisely  the  matter  at  issue.  It  is 
silently  assumed  that  glaciers  would  not,  if  their  work  were 
interrupted  at  any  accidental  stage,  leave  knobs  on  their  channel 
beds  ;  yet  no  evidence  is  given  to  prove  that  the  transformation 
of  normal  pre-glacial  valleys  into  well-rounded  glacial  troughs  is 
not  a  progressive  work,  which  would  show  many  signs  of  being 
unfinished  if  time  enough  had  not  been  allowed  for  the  finishing. 
It  is  silently  assumed  that  the  production  of  rough  ledges  on  the 
down-valley  side  of  a  knob  are  not  within  the  possibilities  of 
glacial  erosion  ;  but  there  is  much  evidence  that  a  glacier  may 


630  PHYSIOGRAPHIC  ESSAYS 

roughen  one  side  of  a  rock  mass  by  dragging  or  plucking  away 
large  blocks,  while  it  smooths  the  other  side  by  scouring  down 
preexistent  irregularities. 

Insufficiency  of  the  Explanations  of  Special  Forms  without 
Glacial  Erosion.  Some  of  the  explanations  offered  by  non- 
glacial  erosionists  for  those  peculiar  forms  of  glaciated  moun- 
tains here  ascribed  to  glacial  erosion  may  now  be  presented. 

Large  lakes,  such  as  those  which  are  piedmont  to  the  Alps, 
are  explained  by  the  warping  or  local  depression  of  pre-glacial 
valleys  with  subordinate  aid  from  morainic  barriers.  The  argu- 
ment presented  by  Wallace  against  this  view  seems  to  me  con- 
clusive. If  the  lake  basins  are  formed  by  the  warping  or 
damming  of  essentially  unmodified  pre-glacial  valleys,  the  lake 
water  should  invade  numerous  side  valleys,  and  thus  form 
lateral  bays  ;  for  the  side  valleys  must  have  been,  in  pre-glacial 
time,  worn  down  to  accordant  junction  with  their  maturely  wide- 
open  main  valleys.  It  is  well  known  that  the  Alpine  lakes  are 
singularly  deficient  in  lateral  bays.  To  test  the  value  of  this 
evidence,  let  any  never-glaciated  mountain  range  be  examined 
to  see  what  sort  of  a  lake  would  be  formed  by  warping  or 
damming  one  of  the  larger  valleys  at  the  mountain  base.  The 
contrast  between  such  a  lake  and  the  Alpine  lakes  is  most 
striking.  But  it  should  be  carefully  borne  in  mind  that  in  the 
present  explanation  of  piedmont  lakes  by  glacial  erosion,  it  is 
not  only  the  lake  basin,  as  Ramsay  believed,  but  much  of  the 
valley  depth  and  breadth  within  the  mountains  that  has  been 
worn  out  by  ice  action. 

Cirques  and  the  sharpened  summit  forms  often  associated 
with  them  have  had  so  little  close  study,  except  by  those  who 
regard  them  as  directly  or  indirectly  of  glacial  origin,  that  they 
need  not  be  further  considered  here. 

Hanging  lateral  valleys,  opening  in  the  over-steepened  walls  of 
over-deepened  main-valley  troughs,  have  had  several  explanations. 
One  of  the  most  recent  writers  on  this  subject  doubts  whether 
hanging  valleys  are,  after  all,  of  so  striking  a  character  and  of  so 
peculiar  a  distribution  as  to  constitute  serious  evidence  for  glacial 
erosion  ;  he  suggests  that,  for  those  which  do  exist,  some  peculiar 
and  sufficient,  though  now  unknown,  explanation  will  probably  be 


THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS     631 

found,  without  having  recourse  to  anything  so  extravagant  as  the 
deepening  of  the  main-valley  trough  by  ice  action.  This  is  simply 
a  series  of  skeptical  assumptions  and  vague  suggestions  that  need 
not  be  answered  until  they  are  made  more  specific. 

Another  writer,  recognizing  the  hanging  attitude  of  lateral 
valleys  as  characteristic  of  Alpine  valley  systems,  suggests  that 
the  lateral  valleys  were  occupied  and  protected  from  erosion  by 
glaciers,  while  the  main  valley  was  deepened  by  normal  river 
erosion.  One  objection  to  this  is  its  extreme  improbability  ;  for 
a  series  of  independent  glaciers  could  not  agree  to  hold  their  ends 
at  the  mouths  of  the  lateral  valleys  for  a  time  long  enough  for 
the  main  valley  to  be  deepened  by  hundreds,  and  widened  by 
thousands,  of  feet  below  their  level.  Another  objection,  lately 
pointed  out  by  Penck,  is  that  hanging  laterals  occur  not  only 
where  both  trunk  and  lateral  valleys  were  glaciated,  but  also  in 
certain  parts  of  the  Alps  where  only  the  main  valley  was 
glaciated ;  in  the  .latter  case,  the  protection  of  the  lateral 
valleys  against  erosion  by  the  presence  of  lateral  glaciers  can- 
not be  assumed. 

A  third  explanation  is  to  the  effect  that  lateral  valleys  will  be 
left  "hanging,"  if  the  region  in  which  they  occur  be  tilted  so  as 
to  steepen  the  slope  of  the  main  river  but  not  of  its  branches. 
Apart  from  the  sufficient  objections  that  may  be  urged  against 
this  explanation,  in  view  of  the  general  principles  of  river 
action,  it  is  pertinent  and  logical  to  ask  that  the  possibility 
of  such  an  origin  for  hanging  lateral  valleys  should  be  tested 
in  a  region  where  tilting  can  be  proved  on  independent  grounds, 
and  where  glacial  action  has  not  taken  place ;  indeed,  one  might 
fairly  expect  that  the  advocates  of  this  explanation  would  be  the 
first  to  test  it  in  a  non-glaciated  region  before  putting  faith  in 
it,  but  they  do  not  seem  to  have  done  so.  It  might  be  tested 
in  the  southwestern  slope  of  the  central  massif 'of  France,  or  in 
the  piedmont  belt  of  the  southeastern  United  States,  where  the 
revival  of  valley  erosion  by  regional  tilting  cannot  be  doubted  ; 
but  no  hanging  lateral  valleys  occur  there,  although  the  main 
valleys  are  often  of  so  moderate  a  width  as  to  indicate  that  they 
have  been  exposed  to  erosion  for  a  much  shorter  time  than  that 
which  would  be  required  by  normal  erosion  in  producing  the 


632  PHYSIOGRAPHIC  ESSAYS 

wide  main  valleys  above  which  the  lateral  valleys  hang  so  con- 
spicuously in  glaciated  mountains.  Hence,  if  a  relatively  short 
time  has  sufficed  for  the  lateral  streams  to  wear  down  their 
valley  mouths  as  deep  as  the  main  valleys  in  these  non-glaciated 
districts,  a  longer  time  should  certainly  have  sufficed  to  bring 
about  accordant  j  unctions  of  lateral  and  main  valleys  in  glaciated 
mountain  ranges,  on  the  supposition  that  normal  erosion  has 
alone  been  operative  there.  The  fact  that  such  accordant  valley 
junctions  do  not  prevail  in  glaciated  ranges  shows  that  the  sup- 
position just  stated  is  erroneous. 

A  fourth  explanation  remains  to  be  mentioned,  and  this,  in 
its  relations  to  the  whole  question  of  land  sculpture,  seems  to 
me  the  most  peculiar  of  all.  This  explanation  asserts  that 
when  local  rains  occur,  they  will  contribute  to  the  erosion  of 
only  certain  of  the  lateral  valleys,  while  the  main  valley  will 
always  receive  some  of  the  local  rainfall,  and  hence  will  always 
suffer  some  erosion  at  such  times  ;  therefore  the  main  valley 
will  be  eroded  faster  than  the  laterals,  which  will  consequently 
be  left  "hanging."  This  is  tantamount  to  saying  that  hanging 
lateral  valleys  are  normal  features,  to  be  expected  in  all  moun- 
tain ranges  as  the  result  of  the  normal  processes  of  erosion. 
Such  a  conclusion  is  contrary  to  experience  and  to  the  well- 
based  principles  of  land  sculpture.  It  gainsays  Playfair's  law, 
which  is  one  of  the  best  established  generalizations  in  physio- 
graphic geology.  It  takes  the  Alps,  a  strongly  glaciated  range, 
as  an  example  of  normal  mountain  sculpture,  and  thus  begs  the 
very  question  in  discussion.  It  is  here  characterized  as  the 
most  peculiar  of  all  the  explanations  offered  for  hanging  valleys, 
because  it  goes  so  directly  counter  to  observation  in  other  than 
glaciated  regions.  It  is,  of  course,  not  to  be  forgotten  for  a 
moment  that  a  large  trunk  river  may,  in  its  youth,  cut  down  its 
valley  faster  than  the  smaller  side  streams  can  cut  down  theirs, 
and  thus  introduce  a  hanging  arrangement  of  lateral  valleys 
with  respect  to  the  trunk  valley ;  but  it  must  also  not  be  for- 
gotten that  as  soon  as  the  trunk  river  approaches  grade,  the 
further  deepening  of  its  valley  is  greatly  retarded  ;  and  that 
then,  while  the  trunk  river  devotes  its  energy  (apart  from  that 
of  transportation)  chiefly  to  widening  its  valley  floor,  the  side 


THE  SCULPTURE  OF  MOUNTAINS  BY  GLACIERS    633 

streams  overtake  it  and  develop  accordant  junctions  of  lateral 
and  trunk  valleys.  It  needs  but  little  observation  in  non- 
glaciated  areas  to  see  that  the  chapter  of  early  youth,  in  which 
a  trunk  river  may  be  deeper  than  the  mouths  of  the  lateral 
valleys,  is  very  short ;  that  this  peculiar  relation  only  appears 
when  the  contrast  between  the  volumes  of  trunk  river  and  side 
stream  is  great ;  and  that  in  all  examples  of  non-glaciated 
mountains  and  plateaus,  an  accordant  relation  of  lateral  and 
main  valley  floors  obtains  as  soon  as  the  main  valleys  acquire 
a  significant  breadth.  The  last  point  is  of  essential  importance, 
because  in  all  the  examples  of  hanging  lateral  valleys  of  glaciated 
'mountains  yet  described,  the  main  valley  is  not  a  narrow  cleft, 
in  which  hanging  laterals  would  be  normally  appropriate,  but  a 
well-opened  valley  with  respect  to  which  hanging  laterals  are 
normally  most  inappropriate.  In  the  Alps,  the  main  valleys  are 
half  a  mile,  a  mile,  or  over  a  mile  in  width.  It  is  entirely  out  of 
the  question  to  ascribe  the  over-deepening  of  these  wide  valleys 
to  any  normal  process,  independent  of  glacial  action. 

As  to  various  other  explanations  of  hanging  valleys,  they  are 
essentially  irrelevant.  Sea  cliffs,  strongly  under-cut  by  surf,  may 
have  valleys  opening  in  their  faces  in  .hanging  fashion  ;  but  this 
has  no  possible  bearing  on  the  hanging  valleys  of  glaciated 
mountains.  Faults  may  occasionally  be  found,  recent  enough 
in  date  to  dislocate  the  valley  floors  that  they  traverse  ;  but 
they  should  dislocate  mountain  flanks  and  ridges  also.  To  sup- 
pose that  the  numerous  hanging  valleys  of  glaciated  mountains 
are  of  this  origin  involves  special  conditions,  at  once  so  numerous 
and  so  improbable  that  to  state  them  is  to  discredit  them. 

A  Fallacy  leading  to  a  Quandary.  In  fine,  it  remains  only 
to  point  out  the  two  positions,  on  one  or  the  other  of  which 
there  is  refuge  for  those  conservatives  who,  on  the  ground  of 
the  apparent  inefficiency  of  existing  glaciers  to  erode  their  beds, 
hesitate  to  conclude  that  the  piedmont  lake  basins,  the  over- 
deepened  main  valleys,  the  hanging  side  valleys,  the  valley-head 
cirques,  and  the  sharpened  peaks  of  glaciated  mountains  are  the 
work,  directly  or  indirectly,  of  ancient  glaciers.  The  conserva- 
tives may,  on  the  one  hand,  attempt  to  explain  by  normal 
erosive  processes,  as  has  just  been  suggested,  the  features 


634  PHYSIOGRAPHIC  ESSAYS 

which  are  here  classed  as  peculiar  ;  but  so  long  as  the  peculiar 
features  are  found  only  in  glaciated  mountains,  and  so  long  as 
normal  processes  are  not  shown  to  be  capable  of  producing 
them,  the  offered  explanations  by  normal  processes  must  be 
doubted.  On  the  other  hand,  the  conservatives  who  hesitate  to 
accept  glacial  erosion  may  suppose  that  in  pre-glacial  times 
some  special  agency  or  conspiracy  of  agencies,  not  now  known, 
prophetically  selected  all  those  mountainous  regions  that  were 
afterwards  to  be  glaciated,  worked  upon  them  in  essentially  the 
manner  that  glaciers  would  work  if  they  could,  and  then  with- 
drew into  obscure  inactivity.  But  this  is  incredible,  because  the 
unknown  agency  or  agencies  could  not  possibly  have  been  so 
circumspect  as  to  produce  only  small  cirques  and  short  trough 
valleys  in  the  high  mountains  of  low  latitudes  and  in  the  lower 
mountains  of  middle  latitudes  ;  to  produce,  in  the  high  moun- 
tains of  middle  latitudes  and  in  the  lower  mountains  of  high 
latitudes,  large  cirques  and  long  main- valley  troughs,  over  which 
the  side  valleys  open  in  the  most  significant  hanging  fashion  ; 
and  to  produce  in  these  valleys  and  their  cirque  heads  a 
great  number  of  rock  basins  in  which  lakes  now  stand.  Either 
one  of  these  refuges  for  the  conservative  is  so  uncomfortable 
a  quandary  that  the  road  leading  to  it  must  be  regarded  as 
lying  on  fallacious  ground. 

It  is  thus  both  along  direct  and  indirect  lines  of  evidence  that 
many  observers  have  .been  led  in  recent  years  away  from  the 
supposition  that  glaciers  cannot  erode,  and  toward  the  supposi- 
tion that  glaciers  can  erode,  even  though  the  methods  of  glacial 
erosion  are  not  yet  fully  understood.  The  sculpture  of  moun- 
tains by  glaciers  is  indeed  now  proved  by  so  many  facts,  widely 
and  yet  systematically  distributed,  that  it  savors  of  extreme  con- 
servatism any  longer  to  deny  the  efficacy  of  glacial  erosion. 


XXIV 

GLACIAL  EROSION  IN  FRANCE,  SWITZERLAND, 
AND  NORWAY 

Introduction.  Many  years  ago  I  presented  to  the  Boston 
Society  of  National  History  an  essay  on  Glacial  Erosion,  in 
which  my  own  observations  were  supplemented  by  a  review 
of  all  that  I  could  find  written  on  the  subject,  in  the  hope  of 
reaching  some  safe  conclusion  regarding  what  was  then  (as  it  is 
still)  a  mooted  question.  Although  recognizing  effective  erosion 
to  depths  of  "  a  moderate  number  of  feet "  where  ice  pressure 
was  great  and  motion  was  rapid,  in  contrast  to  deposition  where 
pressure  and  motion  were  reduced  and  where  the  amount  of 
sub-glacial  drift  was  excessive,  I  could  not  at  that  time  find 
evidence  to  warrant  the  acceptance  of  great  glacial  erosion, 
such  as  was  advocated  by  those  who  ascribed  Alpine  lakes  and 
Norwegian  fiords  to  this  agency.  In  a  retrospect  from  the 
present  time,  it  seems  as  if  one  of  the  causes  that  led  to  my 
conservative  position  was  the  extreme  exaggeration  of  some 
glacialists,  who  found  in  glacial  erosion  a  destructive  agency 
competent  to  accomplish  any  desired  amount  of  denudation,  — 
an  opinion  from  which  I  recoiled  too  far.  Since  the  publication 
of  my  previous  essay  I  had  gradually  come  to  accept  a  greater 
and  greater  amount  of  glacial  erosion  in  the  regions  of  active 
ice  motion  ;  but  in  spite  of  this  slow  change  of  opinion,  the 
maximum  measure  of  destructive  work  that,  up  to  last  year, 
seemed  to  me  attributable  to  glaciers  was  moderate ;  and  it  was 
therefore  with  great  surprise  that  I  then  came  upon  certain 
facts  in  the  Alps  and  in  Norway  which  demanded  wholesale 
glacial  erosion  for  their  explanation.  The  desire  of  some  years 
past  to  revise  and  extend  my  former  essay  then  came  to  be  a 
duty,  which  it  is  the  object  of  this  paper  to  fulfill. 

My  former  revision  of  the  problem  divided  the  arguments 
for  glacial  erosion  under  four  headings  :  observations  on  existing 

635 


636  PHYSIOGRAPHIC   ESSAYS 

glaciers  and  inferences  from  these  observations  ;  the  amount 
and  arrangement  of  glacial  drift  ;  the  topography  of  glaciated 
regions  ;  and  the  so-called  argument  from  necessity,  that  is, 
the  belief  that  glaciers  must  have  done  this  and  that  because 
nothing  else  competent  to  the  task  could  be  found.  It  is  not 
possible  for  me  at  present  to  review  all  the  new  material  perti- 
nent to  the  whole  problem  ;  attention  can  be  given  here  chiefly 
to  a  few  examples  under  the  third  heading. 

A  Glaciated  Valley  in  Central  France.  It  is  evident  that  if  it 
were  possible  to  obtain  a  definite  idea  of  the  pre-glacial  topog- 
raphy of  a  glaciated  district,  the  amount  of  glacial  work  might 
be  readily  determined  as 'the  difference  between  the  pre-glacial 
and  the  present  form  ;  independent  evidence  sufficing  to  prove 
that  general  denudation  of  the  rocky  crust  in  the  brief  post- 
glacial epoch  had  been  inconsiderable.  This  method  leads  one 
to  conclude  that  in  general  the  topography  of  southern  New 
England  has  not  been  strongly  modified  by  glacial  action  ;  for 
we  find  here  on  the  whole  the  same  maturely  dissected  upland 
that  prevails  in  regions  of  similar  structure  outside  of  the 
glacial  boundary,  the  uplands  being  explained  as  parts  of  an 
uplifted  peneplain  of  late  Mesozoic  date,  and  the  valleys  as  the 
work  of  ordinary  erosion  in  a  part  of  Tertiary  time ;  but  this 
method  of  measuring  glacial  erosion  by  dating  topographical 
forms  had  not  been  developed  twenty  years  ago.  Strong  glacial 
erosion  may,  however,  be  expected  in  New  England  where  ice 
motion  was  locally  accelerated,  as  through  the  notches  of  the 
White  mountains.  Again,  in  the  glaciated  area  of  the  Central 
Plateau  of  France  I  had  the  opportunity  in  January,  1899,  of 
seeing  a  valley  that  had  been  locally  modified  to  a  determinate 
amount  by  a  glacier  that  once  descended  northwest  from  the 
Cantal  along  the  valley  of  the  Rhue  to  the  junction  of  the  latter 
with  the  Dordogne.  Outside  of  the  glaciated  area  the  valleys 
of  the  plateau  —  an  uplifted  and  sub-maturely  dissected  pene- 
plain, mostly  of  crystalline  rocks  —  frequently  follow  incised 
meandering  courses,  in  which  the  steep  concave  slopes  are 
regularly  opposed  to  the  gentler  convex  slopes,  the  latter  being 
spur-like  projections  of  the  uplands,  advancing  first  from  one  side 
and  then  from  the  other  side  of  the  valley.  Valleys  of  this  kind 


GLACIAL  EROSION 


637 


are  singularly  systematic  in  form,  as  the  result  of  the  combined 
downward  and  outward  cutting  by  their  streams  which,  already 
winding  or  meandering  when  the  erosion  of  the  valleys  began, 
have  increased  the  width  of  their  meander  belt  while  they  deep- 
ened their  valleys.  On  entering  the  glaciated  valley  of  the  Rhue 
it  is  found  that  the  regularly  descending  spurs  characteristic 
of  the  non-glaciated  valleys  are  represented  by  irregular  knobs 
and  mounds,  scoured  on  their  upstream  side  and  plucked  on  the 
downstream  side ;  and  that  the  cliffs  formed  where  the  spurs 
are  cut  off,  as  in  Fig.  100,  are  sometimes  fully  as  strong  as 
those  which  naturally  stand  on  the  opposite  side  of  the  valley. 
The  spurs  generally  remain  in  sufficient  strength  to  require  the 


FIG.  TOO.   THE  GLACIATED  VALLEY  OF  THE  RHUE 

river  to  follow  its  pre-glacial  serpentine  course  around  them, 
but  they  are  sometimes  so  far  destroyed  as  to  allow  the  river 
to  take  a  shorter  course  through  what  was  once  the  neck  of  a 
spur.  But  it  should  be  noted  that  the  short-cuts  are  some- 
times narrow  gorges  incised  in  the  half-consumed  spurs ;  and 
in  such  cases  the  displacement  of  the  Rhue  from  its  former 
roundabout  course  is  probably  to  be  explained  by  constraint  or 
obstruction  by  ice.  The  short-cuts  here  described  are  not  for 
a  moment  to  be  confounded  with  the  normal  cut-offs  through 
the  narrowed  necks  of  spurs,  such  as  are  so  finely  exhibited 
in  the  meandering  valleys  of  the  Meuse  and  the  Moselle. 
The  short  courses  are  distinctly  abnormal  features,  like  the 
rugged  knobs  to  which  the  once  smooth-sloping  spurs  are  now 
reduced. 


638  PHYSIOGRAPHIC   ESSAYS 

It  was  thus  possible  in  the  valley  of  the  Rhue  to  make  a 
definite  restoration  of  pre-glacial  form,  and  to  measure  the 
change  produced  by  glaciation.  The  change  was  of  moderate 
amount,  but  it  was  highly  significant  of  glacial  action,  for  it 
showed  that  while  a  slender,  fast-flowing  stream  of  water  might 
contentedly  follow  a  serpentine  course  at  the  bottom  of  a 
meandering  valley,  the  clumsy,  slow-moving  stream  of  ice  could 
not  easily  adapt  itself  to  so  tortuous  a  path.  The  more  or  less 
complete  obliteration  of  the  spurs  was  the  result  of  the  effort 
of  the  ice  stream  to  prepare  for  itself  a  smooth-sided  trough  of 
slight  curvature  ;  and  if  the  rocks  had  been  weaker,  or  if  the 
ice  had  been  heavier,  or  if  the  glacial  period  of  the  Cantal  had 
lasted  longer,  this  effort  might  have  been  so  successful  as  to 
have  destroyed  all  traces  of  the  spurs.  Fortunately,  the  change 
actually  produced  only  modified  the  spurs,  but  did  not  entirely 
destroy  them  ;  and  their  rugged  remnants  are  highly  significant 
of  what  a  glacier  can  do. 

Rocky  Knobs  in  Glaciated  Areas.  On  thus  generalizing  the 
lesson  of  the  Rhue,  it  is  seen  that  just  before  the  complete 
obliteration  of  the  spurs,  some  of  their  remnant  knobs  may  be 
isolated  from  the  uplands  whence  these  pre-glacial  spurs  de- 
scended. It  is  out  of  the  question  to  regard  the  ruggedness  of 
such  knobs  as  an  indication  of  small  change  from  their  pre- 
glacial  form,  as  has  been  done  by  some  observers.  The  rugged- 
ness  is  really  an  indication  of  the  manner  in  which  a  glacier 
reduces  a  larger  mass  to  smaller  dimensions,  by  plucking  on 
the  downstream  side  as  well  as  by  scouring  on  the  upstream 
side.  It  is  possible  that  knobs  in  other  glaciated  valleys  than 
that  of  the  Rhue  may  be  of  this  origin  ;  they  should  then  be 
regarded  not  as  standing  almost  unchanged  and  testifying  to 
the  incapacity  of  glacial  erosion,  but  as  surviving  remnants  of 
much  larger  masses,  standing,  like  monadnocks  above  a  pene- 
plain, as  monuments  to  the  departed  greater  forms.  The  two 
knobs  at  Sion  (Sitten)  and  the  Maladeires,  all  detached  from 
Mont  d'Orge  in  the  upper  valley  of  the  Rhone,  the  hills  of 
Bellinzona  in  the  valley  of  the  Ticino,  the  rocks  of  Salzburg 
where  the  Salzach  emerges  from  the  Alps,  and  even  the  Borro- 
meo  islands  in  lake  Maggiore,  may  perhaps  be  thus  interpreted. 


GLACIAL  EROSION 


639 


Rugged  as  these  knobs  may  be  on  the  downstream  side,  it 
would  be  an  unreasonable  contradiction  of  the  conclusions 
based  on  observations  of  many  kinds  to  maintain  that  their 
ruggedness  was  of  pre-glacial  origin. 

The  ice  stream  from  the  Cantal  at  one  time  expanded  suffi- 
ciently to  flood  the  uplands  bordering  the  valley  of  the  Rhue, 
where  it  produced  changes  of  a  most  significant  kind.  The 
neighboring  unglaciated  uplands  are  of  systematic  form  ;  broad, 
smoothly  arched  masses  rise,  round-shouldered,  between  the 
narrow  valleys  that  are  incised  beneath  them ;  the  uplands  are, 


FIG.  101.   GLACIATED  KNOBS  ON  THE  CENTRAL  PLATEAU  OF  FRANCE 

as  a  rule,  deeply  soil-covered,  and  bare  ledges  prevail  only  on 
the  stronger  slopes  of  the  young  valleys  that  have  been  eroded 
since  the  peneplain  was  raised  to  its  present  upland  estate.  But 
within  the  glaciated  area  near  the  Rhue  the  broadly  rounded 
forms  of  the  uplands  are  replaced  by  a  succession  of  most 
irregular  rocky  knobs,  from  which  the  pre-glacial  soils  have 
been  well  scoured  away,  as  in  Fig.  101.  This  seems  to  be  a  form 
most  appropriate  to  glacial  action  on  a  surface  that  had  been 
weathered  to  variable  depths  in  pre-glacial  time.  The  ice  action 
sufficed  to  rasp  away  the  greater  part  of  the  weathered  material 
and  to  grind  down  somewhat  the  underlying  rock,  often  giving 
the  knobs  a  rounded  profile,  but  it  did  not  nearly  suffice  to 
reduce  the  rocky  surface  to  an  even  grade.  The  ice  action 


640  PHYSIOGRAPHIC  ESSAYS 

seems  here  to  have  resembled  that  of  a  torrent  which  might 
sweep  away  the  waste  on  a  flood  plain  and  lay  bare  and  erode 
the  rock  ledges  beneath,  but  whose  duration  was  not  sufficient 
to  develop  a  graded  floor  appropriate  to  its  current. 

Another  example  of  this  kind  seems  to  occur  where  the  huge 
glacier  of  the  Inn,  escaping  from  its  well-inclosed  channel  within 
the  mountains,  once  spread  forward  in  a  great  fan  of  ice  over 
the  foothills  at  the  northern  border  of  the  Alps  and  crept  out 
upon  the  piedmont  plain.  The  glance  that  I  had  at  this  foothill 
district  from  a  passing  train  gave  me  the  impression  that  its 
ruggedness  was  much  greater  than  usually  obtains  along  the 
mountain  flanks  ;  as  if  the  rolling  hills  of  pre-glacial  time  had 
been  scoured  to  an  increasing  roughness  by  an  overwhelming 
ice  flood  that  would,  if  a  longer  time  of  action  had  been  per- 
mitted to  it,  have  worn  down  all  the  inequalities  to  a  smooth, 
maturely  graded  floor. 

The  Valley  of  the  Ticino.  My  first  entrance  into  the  Alps 
last  year  was  from  the  south  by  the  valley  of  the  Ticino.  Thirty- 
one  years  before  I  had  followed  the  same  valley  and  admired  its 
bold  sides  and  its  numerous  waterfalls,  but  at  that  time  nothing 
was  noticed  that  seemed  inappropriate  to  the  general  idea  of  the 
erosion  of  valleys  by  their  rivers.  Thirty  years  is  a  long  enough 
time  for  one  to  learn  something  new  even  about  valleys,  and  on 
my  second  visit  it  was  fairly  startling  to  find  that  the  lateral 
valleys  opened  on  the  walls  of  the  main  valley  of  the  Ticino  five 
hundred  feet  or  more  above  its  floor,  and  that  the  side  streams 
cascaded  down  the  steep  main-valley  walls  in  Which  they  have 
worn  nothing  more  than  narrow  clefts  of  small  depth.  This  set 
me  wondering,  not  only  as  to  the  meaning  of  so  peculiar  an 
arrangement  of  valleys  and  streams,  but  also  as  to  the  reason 
why  so  peculiar  an  arrangement  should  not  have  sooner  attracted 
attention  as  an  exceptional  characteristic  of  .Alpine  topography. 
Playfair  long  ago,  when  describing  the  relation  of  side  valleys 
to  their  trunk,  showed  clearly  that  they  had  "  such  a  nice  adjust- 
ment of  their  declivities  that  none  of  them  join  the  principal 
valley  either  on  too  high  or  too  low  a  level ;  a  circumstance 
which  would  be  infinitely  improbable  if  each  of  these  vallies  were 
not  the  work  of  the  stream  that  flows  in  it  "  (102);  yet  the  whole 


GLACIAL  EROSION 


641 


course  of  the  passing  century  has  hardly  sufficed  to  make  full 
application  of  this  law.  So  much  latitude  is  usually  allowed  in 
the  relation  of  branch  and  trunk  valleys  that  hundreds  of  ob- 
servers, many  of  whom  must  have  been  cognizant  of  Playfair's 
law,  have  made  no  note  of  the  extraordinary  exceptions  to  it 
that  prevail  in  the  glaciated  valleys  of  the  Alps.  Even  the  most 
pronounced  advocates  of  glacial  erosion,  with  a  few  exceptions  to 
be  noted  below,  have  been  silent  regarding  the  remarkable  failure 
of  adjustment  between  the 
declivities  of  lateral  and 
main  glaciated  valleys.  In- 
deed, in  reviewing  the  writ- 
ings of  those  who  have 
accepted  a  large  measure  of 
glacial  erosion,  one  must  be 
struck  with  the  undue  atten- 
tion that  they  have  given  to 
lake  basins  and  the  relative 
inattention  to  valleys.  This 
disproportion  is  probably  to 
be  explained  as  a  result  of 
the  greater  contrast  that 
prevails  between  a  river  and 
a  lake  than  between  a  river 
and  its  branch  ;  it  is  perhaps 
for  this  reason  that  the 
attention  of  geologists  and 
geographers  has  'generally 
been  directed  to  the  origin 
of  lakes  rather  than  to  the 

relation  of  branch  and  trunk  streams,  even  when  the  former 
cascade  from  their  lateral  valleys  into  the  main  valley.  That 
glacial  erosionists  made  so  little  claim  for  the  general  deepening 
of  glaciated  valleys  while  they  demanded  a  great  deepening  of 
those  parts  of  valleys  which  have  been  scoured  down  to  form 
lake  basins  has  always  seemed  to  me  a  difficulty  in  the  way  of 
accepting  the  demanded  measure  of  lake-basin  erosion  ;  and  this 
difficulty  was  supported  by  the  well-attested  observation  that  the 


FIG.  102.   VAL  D'OSOGNA,  A  HANGING 
LATERAL  VALLEY  OF  THE  TICINO 


642 


PHYSIOGRAPHIC  ESSAYS 


side  slopes  of  glaciated  valleys  manifest  no  marked  or  persistent 
increase  of  declivity  in  passing  from  above  to  below  the  limit  of 
glaciation.  If  glaciers  had  scoured  out  deep  lake  basins,  like 
those  of  Maggiore  and  Geneva,  they  ought  to  have  significantly 
deepened  the  valleys  upstream  from  the  lakes  ;  and  if  the  val- 
leys were  thus  significantly  deepened,  it  seemed  as  if  their  slopes 
should  be  steeper  below  than  above  the  limit  of  glacial  action. 
The  denial  of  the  latter  requisite  seemed  to  me  to  carry  with 
it  the  denial  of  the  two  preceding  suppositions. 

Features  of  Strongly  Glaciated  Valleys.  It  is  true  that  the 
uppermost  limit  of  glaciation,  QR  (Fig.  103),  in  Alpine  valleys 
is  not  attended  by  a  persistent  change  in  the  steepness  of  the 

valley  sides,  AE,  CJ\  but  on 
descending  well  within  the 
glaciated  valley,  a  very 
strong  change  may  usually 
be  found  in  the  slope  of  the 
valley  walls.  The  larger  val- 
leys, once  occupied  by  heavy 
glaciers  from  the  lofty,  cen- 
tral snow  fields,  are  char- 
acterized by  basal  cliffs,  EF,  JH,  that  rise  several  hundred  or 
even  a  thousand  feet  above  their  broad  floors,  and  thus  inclose 
what  may  be  called  a  bottom  trough,  EFHJ,  half  a  mile  or  a  mile 
wide.  The  bottom  trough  of  the  Ticino,  as  seen  when  one  looks 
upstream  towards  Giornico,  is  a  very  striking  feature.  The 
basal  cliffs  are  comparatively  straight-walled ;  they  have  no 
sharp  spurs  advancing  into  the  valley  floor.  The  rock  floor,  G 
(Fig.  103),  is  buried  by  gravels,  FH,  to  an  unknown  depth.  It 
is  only  from  the  benches  above  the  basal  cliffs  that  the  valley 
sides  flare  open  with  maturely  inclined  slopes  ;  and  it  is  at  a 
moderate  depth  beneath  the  level  of  the  benches  at  the  top 
of  these  basal  cliffs  that  the  lateral  valleys,  DK,  open  on  the 
walls  of  the  main  valley. 

The  bottom  trough  within  the  basal  cliffs  and  beneath  the 
lateral  valleys  seems  to  be  of  glacial  origin.  It  is  in  the  first 
place  a  characteristic  feature  of  all  the  larger  glaciated  Alpine 
valleys,  as  I  am  assured  by  Professors  Penck,  Bruckner,  and 


FIG.  103.   SECTION  OF  A  GLACIATED 
VALLEY 


GLACIAL  EROSION  643 

Richter,  with  whom  this  matter  was  carefully  discussed  one 
summer.  The  non-glaciated  valleys  manifest  no  such  peculiar 
form.  It  is  not  simply  that  the  terminal  portion,  JBK>  of  a  lat- 
eral valley  has  been  cut  off  by  the  glacial  widening  of  the  main 
valley  floor  ;  the  main  valley  has  been  strongly  deepened,  as  is 
assured  by  the  relation  of  its  floor,  FH,  to  the  prolongation  of 
the  floor  of  the  lateral  valley,  KB.  The  first  may  be  several 
hundred  feet — indeed,  in  some  valleys  a  good  thousand  feet  — 
below  the  second.  The  lateral  valleys  must  have  once  entered 
the  main  valley  at  grade,  for  the  flaring  sides  of  the  main  valley 
indicate  maturity  ;  the  side  slopes  AE,  CJ  must  have  once  met 
at  B.  Even  the  lateral  valleys  have  an  open  V-section,  proving 
that  their  streams  had  cut  down  to  a  graded  slope,  DB,  that 
must  have  led  them  to  an  accordant  junction  with  the  main 
river.  Nothing  seems  so  competent  as  glacial  erosion  to  ex- 
plain the  strong  discordance  of  the  existing  valleys. 

The  lateral  as  well  as  the  main  valleys  have  been  glaciated, 
but  the  former  do  not  exhibit  changes  of  form  so  distinctly  as 
the  latter ;  in  the  Ticino  system  the  lateral  valleys  did  not,  as 
far  as  I  saw  them,  seem  to  have  been  much  affected  by  glaci- 
ation,  a  fact  that  may  be  attributed  to  the  small  size  of  their 
branch  glaciers  in  contrast  with  the  great  volume  of  the  trunk 
glacier.  There  is  no  sufficient  evidence  that  the  valley  floor 
between  the  basal  cliffs  has  been  faulted  down  after  the  fashion 
of  a  graben  ;  for  although  this  origin  is  advocated  by  Rothpletz 
(237)  for  the  Linththal,  the  evidence  that  he  adduces  for  the 
limiting  faults  is  not  agreed  to  by  Alpine  geologists  in  general, 
and  the  persistent  association  of  the  bottom  troughs  with  the 
crooked  course  of  preexistent,  maturely  open  valleys  involves 
special  conditions  of  faulting  that  cannot  be  accepted  without 
the  strongest  evidence. 

It  is  not  satisfactory  to  explain  the  bottom  trough  as  having 
been  worn  out  by  normal  trunk-river  erosion,  leaving  the  side 
streams,  as  it  were,  hanging  or  suspended  above  them,  for  to 
admit  such  an  origin  would  be  to  go  counter  to  all  that  has 
been  learned  regarding  the  systematic  development  of  valleys. 
Here  it  is  with  regret  that  I  must  differ  from  the  opinion  of 
two  eminent  Swiss  geologists,  who  explain  the  deepening  of  the 


644  PHYSIOGRAPHIC  ESSAYS 

main  valleys  by  a  revival  in  the  erosive  power  of  the  rivers  as  a 
result  of  a  regional  uplift,  while  they  regard  the  hanging  lateral 
valleys  as  not  yet  accordantly  deepened  by  their  smaller  streams. 
It  is  true  that  narrow  trenches  are  cut  in  the  floors  of  the  hang- 
ing valleys,  showing  that  their  streams  have  made  some  response 
to  the  erosion  of  the  bottom  trough  in  the  main  valley,  and  if 
the  bottom  trough  were  a  narrow  canon,  this  relation  of  trunk 
and  branch  streams  might  be  considered  normal ;  but  if  the 
breadth  as  well  as  the  depth  of  the  bottom  trough  had  been 
acquired  by  normal  river  erosion,  the  side  valleys  should  now, 
it  seems  to  me,  have  been  trenched  much  deeper  than  they  are, 
to  some  such  slope  as  ST  (Fig.  103). 

The  opinions  of  Rutimeyer  and  Heim  on  this  question  are 
as  follows  :  Rutimeyer  gave  an  excellent  account  of  hanging 
lateral  valleys  thirty  years  ago  in  his  description  of  the  valley 
of  the  Reuss  (13-24).  He  recognized  benches,  or  Thalstufen,  on 
each  side  of  the  valley  above  the  basal  cliffs  of  the  existing 
bottom  trough,  and  regarded  them  as  the  remnants  of  a  former, 
wide-open  valley  floor.  Side  valleys  of  moderate  fall  enter  the 
main  valley  about  at  the  level  of  the  Thalstufen,  and  their  waters 
then  cascade  down  over  the  basal  cliffs  to  the  Reuss.  Glacial 
erosion  is  dismissed  as  incompetent  to  erode  the  bottom  trough ; 
indeed,  the  time  of  glacial  occupation  of  the  valley  is  considered 
a  period  of  rest  —  a  sort  of  "  pupa  stage  "  —  in  its  development. 
The  discordance  of  main  and  lateral  valleys  is  ascribed  entirely 
to  the  differential  erosion  of  their  streams.  Heim's  views  on 
this  matter  are  to  be  found  in  his  "  Mechanismus  der  Gebirgs- 
bildung"  (a,  I,  282-301)  and  in  an  article  "  Ueber  die  Erosion  im 
Gebiete  der  Reuss"  {&).  He  recognizes  that  the  bottom  troughs 
have  been  excavated  in  the  floors  of  preexisting  valleys,  whose 
stream  lines  had  been  reduced  to  an  even  grade  (profile  of  equi- 
librium, Gleichgewichtslinie]  and  whose  lateral  slopes  had  been 
maturely  opened.  The  side  streams  must  at  that  time  have 
eroded  their  valleys  deep  enough  to  enter  the  main  valley  at 
accordant  grade,  as  stated  above.  Since  then  it  is  concluded 
that  an  elevation  of  the  region  has  caused .  a  revival  (Neubcle- 
bung)  of  the  main  river ;  and  the  present  greater  depth  of  the 
main  valley  is,  according  to  Heim,  merely  the  natural  result  of 


GLACIAL  EROSION  645 

this  revival,  while  the  smaller  side  streams  have  not  yet  been 
able  to  deepen  their  valleys.  The  height  of  the  Thais tuf en  or 
remnants  of  the  former  valley  floor,  seen  in  the  benches  above 
the  basal  cliffs  of  the  bottom  trough,  is  taken  as  a  measure  of 
the  elevation  that  the  mountain  mass  has  suffered. 

Apart  from  the  improbability  that  the  deepening  of  a  bottom 
trough  by  a  revived  main  river  could  truncate  so  many  lateral 
valleys  with  so  great  nicety  as  is  repeatedly  the  case,  leaving 
their  streams  to  cascade  down  in  clefts  but  slightly  incised  in 
the  main-valley  walls,  the  following  considerations  lead  me  to 
reject  the  possibility  of  explaining  the  discordance  between 
side  and  main  streams  by  a  normal  revival  of  river  action. 

Relation  of  Trunk  and  Branch  Valleys.  The  general  accord- 
ance of  maturely  developed  main  and  lateral  valleys  in  non-glaci- 
ated regions,  as  recognized  by  Playfair,  is  to-day  fully  established 
by  innumerable  observations  in  many  parts  of  the  world.  Truly, 
during  the  attainment  of  mature  development  it  is  possible  that 
a  large  river  may  outstrip  a  small  branch  stream  in  the  work 
^>f  deepening  its  valley,  but  the  discordance  thus  produced  can 
prevail  only  during  early  youth  ;  for  as  soon  as  the  main  river 
approaches  grade,  the  further  deepening  of  its  valley  is  retarded, 
while  at  the  same  time  the  steepened  descent  of  the  lateral 
streams  at  their  entrance  into  the  main  valley  accelerates  their 
erosive  work.  Hence,  even  if  a  large  trunk  river  has  for  a  time 
eroded  its  valley  to  a  significant  depth  beneath  the  tributary 
valleys,  this  discordance  cannot  endure  long  in  the  history  of 
the  river.  Examples  of  such  normal  discordance  are  to  be  found 
in  non-glaciated  regions  only  in  the  branch  streams  of  rivers  that 
occupy  very  narrow  canons  ;  and  even  rivers  in  canons  sometimes 
receive  their  branches  at  accordant  grade,  as  seems  to  be  usu- 
ally the  case  with  the  Colorado,  if  one  may  judge  by  photographs. 
The  narrow,  post-glacial  gorges  cut  by  active  streams  habitually 
receive  their  branches  —  when  they  receive  any — from  hanging 
side  gorges  ;  and  an  excellent  example  has  long  since  been  on 
record  in  the  gorge  of  Cattaraugus  Creek  in  western  New  York, 
where  a  branch,  the  Canaserowlie,  falls  into  the  main  gorge  from 
a  side  gorge  of  much  less  depth.  Referring  to  this,  Hall  wrote  : 
"  In  the  more  recently  excavated  channels  we  find  the  streams 


646  PHYSIOGRAPHIC  ESSAYS 

falling  over  the  very  edge  of  the  cliff,  having  produced  no  per- 
ceptible recession  in  the  margin  of  the  fall  "  (380).  But  however 
appropriate  a  discordance  of  branch  and  trunk  may  be  in  early 
youth,  it  cannot  endure  long  enough  to  be  associated  with  ma- 
turely opened  main  valleys.  It  should  be  noted  that  discordance 
of  side  and  main  valleys  may  also  be  found  where  a  large  river 
has  lately  been  turned  to  a  new  path,  as  in  the  normal  progress 
of  the  capture  of  the  upper  course  of  one  river  by  the  head- 
ward  gnawing  of  a  branch  of  another  river  (see  reference  to 
Russell  below),  or  in  the  new  arrangements  of  drainage  lines  in 
a  region  from  which  a  glacial  sheet  has  lately  withdrawn.  Fur- 
thermore, the  valleys  of  very  small  wet- weather  streams  are  fre- 
quently discordant  with  the  valley  of  a  serpentine  river,  if  they 
enter  it  from  the  upland  that  is  under-cut  by  the  concave  bank 
of  the  river.  But  these  cases  cannot  find  application  in  the 
hanging  valleys  of  the  Alps.  The  hanging  valleys  that  open  on 
sea  cliffs,  such  as  those  of  Normandy,  are  of  course  quite  an- 
other matter. 

Over-deepened  Main  Valleys  and  Hanging  Lateral  Valleys. 
Now  it  is  characteristic  of  the  bottom  troughs  of  the  glaciated 
Alpine  valleys  that  they  are  broad-floored ;  they  cannot  be  de- 
scribed as  canons  in  any  proper  sense  of  that  word  ;  the  walls 
are  steep  enough,  but  they  are  too  far  apart.  If  the  existing 
breadth  of  the  troughs  had  been  acquired  in  the  ordinary  man- 
ner by  the  lateral  swinging  of  the  main  stream  and  by  the  lateral 
weathering  of  the  walls,  the  long  time  required  for  such  a  change 
would  have  amply  sufficed  for  the  lateral  streams  to  cut  down 
their  valleys  to  grade  with  the  main  valley  ;  and  their  persist- 
ent failure  to  do  so  indicates  the  action  of  something  else  than 
normal  river  work  in  the  widening  of  the  main  valley.  This  is 
the  very  kernel  of  the  problem. 

If  a  main  valley  were  excavated  along  a  belt  of  weak  rocks, 
the  side  valley  might  stand  for  some  time  at  a  considerable 
height  above  the  main-valley  floor.  Certain  hanging  valleys  in 
the  Alps  seem  at  first  sight  to  belong  to  this  class,  but  such  is 
not  really  the  case.  For  example,  where  the  Linth  flows  into 
the  Wal\en  See,  the  well-defined  bottom  troughs  of  the  river 
and  of  the  lake  both  pass  obliquely  through  a  syncline  of  strong 
Walen-See 


GLACIAL  EROSION  647 

lower  Cretaceous  limestone,  which  forms  cliffs  on  their  walls. 
Side  streams  drain  the  high  synclinal  areas ;  one  such  stream 
cascades  from  the  west  into  the  Linth  trough  back  of  the  vil- 
lage of  Naf els  ;  another  cascades  from  the  north  into  the  Wal/en 
See  near  its  western  end.  The  first  explanation  for  such  falls  is 
that  they  are  normally  held  up  on  the  resistant  limestone ;  tut 
it  should  be  noted  that  the  bottom  troughs  of  the  Linth  and  the 
Wallen  See  have  been  cut  down  and  broadly  opened  in  the  same 
limestones.  If  the  troughs  were  of  normal  river  origin,  the  side 
streams,  also,  should  have  by  this  time  trenched  the  limestones 
deeply  instead  of  falling  over  the  limestone  cliffs  at  the  very 
side  of  the  larger  troughs.  In  the  Ticino  valley  where  the  side 
streams  are  most  discordant,  massive  gneisses  prevail ;  the  struc- 
ture is  so  nearly  uniform  over  large  areas  that  it  affords  no  expla- 
nation of  the  strong  discordance  between  side  and  main  valleys. 

It  thus  seems  obligatory  to  conclude  that  the  bottom  troughs 
of  the  larger  Alpine  valleys  were  deepened  and  widened  by  ice 
action.  This  belief  is  permitted  by  the  abundant  signs  of  glacial 
erosion  on  the  spurless  basal  cliffs,  and  required  by  the  persist- 
ent association  of  over-deepened  bottom  troughs  and  discordant 
hanging  lateral  valleys  with  regions  of  strong  glaciation.  The 
valley  of  the  Ticino  manifests  these  peculiarities  very  distinctly, 
as  described  in  some  detail  in  a  paper  in  Appalachia  (Davis). 

Sub-aerial  Erosion  during  the  Glacial  Period,  It  should  not 
be  imagined  that  the  glacial  erosion  of  troughs  in  valley  floors 
was  necessarily  so  rapid  that  no  significant  sub-aerial  erosion 
was  accomplished  during  its  progress.  Ordinary  weathering  and 
down-hill  transportation  of  rock  waste  must  have  been  in  active 
operation  on  the  valley  sides  above  the  border  of  the  ice-filled 
channels  ;  and  the  very  fact  that  on  the  upper  slopes  of  the 
mountains  pre-glacial,  glacial,  and  post-glacial  erosion  was  simi- 
larly conditioned,  makes  it  difficult  to  distinguish  the  work  done 
there  in  each  of  these  three  chapters  of  time.  In  the  diagrams 
accompanying  this  essay  no  indication  of  change  from  pre- 
glacial  to  post-glacial  outline  on  the  upper  mountain  slopes  is 
indicated,  because  no  satisfactory  measure  can  be  given  to  it. 

Lake  Lugano.  In  the  presence  of  a  variety  of  evidence  col- 
lected for  some  years  previous  to  my  recent  European  trip,  it 


648  PHYSIOGRAPHIC  ESSAYS 

had  been  my  feeling  that  the  best  explanation  offered  for  the 
large  lakes  that  occupy  certain  valleys  on  the  Italian  slope  of 
the  Alps  was  that  they  had  resulted  from  what  has  been  called 
valley-warping,  as  set  forth  by  Lyell,  Heim,  and  others.  It  was 
my  desire  to  look  especially  at  lakes  Maggiore,  Lugano,  and 
Como  with  this  hypothesis  in  mind,  and  to  subject  it  to  a  care- 
ful test 'by  means  of  certain  associated  changes  that  should  ex- 
pectedly  occur  on  the  slopes  of  the  neighboring  mountains,  as 
may  be  explained  as  follows : 

On  the  supposition  of  moderate  or  small  glacial  erosion,  a 
well-matured  stage  of  dissection  must  have  been  attained  in 
the  district  of  the  Italian  lakes  in  pre-glacial  time ;  for  the  main 
valleys  are  widely  opened,  and  even  the  lateral  valleys  have  flar- 
ing slopes.  In  a  mature  stage  of  dissection  mountains  should 
exhibit  a  well-advanced  grading  of  their  slopes ;  that  is,  their 
sides  should  be  worn  back  to  a  comparatively  even  declivity  with 
little  regard  to  diversity  of  structure ;  the  descending  streams 
of  waste  being  thus  seen  to  correspond  to  the  flood  plains  of 
graded  rivers.  The  agencies  of  weathering  and  transportation 
are  delicately  balanced  wherever  graded  slopes  prevail ;  and  a 
slight  tilting  of  the  mountain  mass  might  suffice  to  disturb  the 
adjustment  between  the  supply  and  the  removal  of  waste ;  then 
all  the  steepened  slopes  would  soon  be  more  or  less  completely 
stripped  of  their  waste  cover ;  their  rock  ledges  would  be  laid 
bare,  although  still  preserving  the  comparatively  even  declivity 
that  had  been  gained  under  the  slowly  moving  waste. 

If  the  lakes  had  been  formed  by  warping,  it  is  possible  to  de- 
duce with  considerable  accuracy  the  localities  where  the  mountain 
slopes  would  be  steepened  and  stripped  ;  namely,  the  northern 
slopes  about  the  southern  end  of  the  lakes,  and  the  southern  slopes 
about  the  northern  end ;  but  as  far  as  I  was  able  to  examine  the 
district  about  lake  Lugano,  no  effects  of  such  a  warping  and 
tilting  were  to  be  detected.  The  submergence  of  lateral  valleys 
about  the  middle  of  the  lakes  is  also,  as  has  been  well  pointed  out 
by  Wallace,  a  necessary  consequence  of  the  theory  of  warping ; 
but  although  the  main-valley  floor  is  now  deep  under  water,  the 
side  valleys  are  not  submerged.  Failing  to  find  evidence  of  warp- 
ing, and  being  much  impressed  with  the  evidence  of  deep  glacial 


GLACIAL  EROSION  649 

erosion  as  indicated  by  the  hanging  lateral  valleys  of  the  over- 
deepened  Ticino,  I  examined  the  irregular  troughs  of  lake  Lu- 
gano for  similar  features  and  found  them  in  abundance. 

One  of  the  reasons  why  lake  Lugano  had  been  selected  for 
special  study  was  that  it  did  not  lie  on  the  line  of  any  master 
valley  leading  from  the  central  Alps  to  the  piedmont  plains ; 
hence,  if  influenced  by  ice  action  at  all,  its  basin  must  have  been 
less  eroded  than  those  of  Como  and  Maggiore  on  the  east  and 
west.  But  in  spite  of  this  peculiarity  of  position,  Lugano  received 
strong  ice  streams  from  the  great  glaciers  of  the  Como  and  Mag- 
giore troughs  (see  Glacial  Distributaries  below),  and  its  inclosing 
slopes  possess  every  sign  of  having  been  strongly  scoured  by  ice 
action.  The  sides  of  the  lake  trough  are  often  steep  and  cliff-like 
for  hundreds  of  feet  above  present  water  level,  thus  simulating 
the  basal  cliffs  of  the  Ticino  valley;  while  at  greater  heights  the 
valley  sides  lean  back  in  relatively  well-graded  slopes.  The  angle 
at  the  change  of  slope  is  of  ten  well  defined,  but  it  is  independent 
of  rock  structure.  Narrow  ravines  are  frequently  incised  in  the 
basal  cliffs,  and  alluvial  fans  of  greater  or  less  size  are  built 
into  the  lake  waters  from  the  base  of  the  ravines. 

The  northeastern  arm  of  the  lake,  extending  from  the  town 
of  Lugano  to  Porlezza,  receives  several  cascading  streams  from 
hanging  valleys  on  its  southern  side.  The  side  slopes  of  the  hang- 
ing valleys  are  for  the  most  part  flaring  open  and  well  graded, 
from  which  it  must  be  concluded  that  their  streams  had,  under 
some  condition  no  longer  existing,  ceased  to  deepen  their  valleys 
for  a  time  long  enough  to  allow  the  valley  sides  to  assume  a 
mature  expression ;  and  that  since  then  the  bottom  trough  of 
the  main  arm  of  the  lake  has  been  eroded  deep  and  wide,  with 
a  very  small  accompanying  change  in  the  lateral  valleys.  In 
other  words,  the  side  valleys  were,  in  pre-glacial  time,  eroded  to 
a  depth  accordant  with  the  floor  of  the  master  valley  that  they 
joined,  and  since  then  the  bottom  trough  has  been  eroded  in  the 
floor  of  the  master  valley  by  a  branch  of  the  Como  glacier.  In 
post-glacial  time  the  side  streams  have  begun  to  trench  their 
valley  floors,  eroding  little  canons ;  but  much  of  this  sort  of 
work  must  be  done  before  the  side  valleys  are  graded  down 
even  as  far  as  the  surface  of  the  lake. 


650  PHYSIOGRAPHIC  ESSAYS 

The  two  southern  arms  of  the  lake  lead  to  troughs  whose 
floors  ascend  southward  to  the  moraines  of  the  foothills,  beyond 
which  stretch  forward  the  abundant  overwashed  gravels  of  the 
great  plain  of  the  Po. 

I  do  not  mean  to  imply  that  every  detail  of  form  about  lake 
Lugano  can  find  ready  explanation  by  the  mature  glacial  modifi- 
cation of  a  mature  pre-glacial  valley  system,  but  a  great  number 
of  forms  may  be  thus  explained,  and  a  belief  in  strong  glacial 
erosion  was  forced  upon  me  here  as  well  as  in  the  valley  of  the 
Ticino.  A  detailed  study  of  the  Italian  lakes  with  the  intention 
of  carefully  sorting  out  all  the  glacial  modifications  of  pre-glacial 
forms  would  be  most  profitable. 

Various  Examples  of  Glaciated  Valleys.  During  my  excur- 
sions I  have  observed  a  number  of  over-deepened  main  valleys 
and  hanging  lateral  valleys  in  the  Alps  ;  for  example,  those  of  the 
Inn  and  of  the  Aar.  Lakes  Thun  and  Brienz  receive  numerous 
cascades  from  hanging  valleys  that  stand  high  above  the  water 
surface.  The  valley  of  Lauterbrunnen  also  affords  a  conspicuous 
illustration  of  a  deep  bottom  trough  inclosed  by  high  basal  cliffs 
that  rise  to  the  edge  of  more  open  upper  slopes  ;  the  celebrated 
Staubbach  fall  is  the  descent  of  a  small  lateral  stream  from  its 
lofty  hanging  valley  (see  extract  from  an  article  by  Wallace, 
cited  below),  and  the  picturesque  village  of  Miirren,  J/(Fig.  104), 
stands  on  the  flaring  slope,  or  Thalstufe,  of  the  pre-glacial  valley, 
just  above  the  great  basal  cliff  of  glacial  origin.  A  mile  or  so 

south  of  the  village  of  Lauterbrun- 
nen, the  Trummelbach,  J'(Fig.  104), 
descends  the  precipitous  eastern  wall 
from  a  hanging  valley  whose  floor  is 
hundreds  of  feet  above  that  of  the 
Liitschine  ;  it  is  roughly  sketched  in 
Fig.  105.  Although  the  lateral  Trum- 

lOOOMet.  „         :_     ,      .  ,  ,  r 

melbach  brings  a   large  volume  of 


FIG.  104.  TRUE-SCALE  CROSS      water  to  the  main  valley,  it  descends 
SECTION  OF  THE  LAUTER-         ^y  a  very  narrow  cleft  in  the  rock 

BRUNNEN  VALLEY  r  ,n ^,  n 

face,  a  trifling  incision  in  the  valley 

wall ;  while  the  main  valley,  whose  trunk  stream  did  not  seem 
to  be  more  than  five  times  the  volume  of  its  branch,  is  half  a 


GLACIAL  EROSION 


65' 


FIG.  105.   DIAGRAM  OF  THE 

GORGE  OF  THE  TRUMMEL- 

BACH,  LAUTERBRUN- 

NEN  VALLEY 


mile  or  more  broad,  wide  open,  and  flat-floored.  The  cross  sec- 
tion of  the  main  valley  is  over  a  thousand  times  as  large  as  that 
of  the  lateral  cleft.  Such  a  disproportion  of  main  valley  and 
lateral  cleft  is  entirely  beyond  ex- 
planation by  the  inequality  of  their 
streams  ;  and  for  those  who  feel  that 
they  must  reject  glacial  erosion  as 
the  cause  of  the  disproportion,  there 
seems  to  be  no  refuge  but  in  ascrib- 
ing the  main  valley  to  recent  down- 
faulting, —  a  process  that  can  hardly 
be  called  on  to  follow  systematically 
along  the  floors  of  the  larger  glaci- 
ated valleys  of  the  Alps,  and  to  avoid 
the  non-glaciated  valleys  and  the 
mountain  ridges. 

Certain  well-known  Alpine  glaciers 
may  be  instanced  as  reaching  just 
beyond  the  end  of  a  hanging  lateral 
valley  and  thence  cascading  into  the  deeper  main  valley.  One  is 
the  Mer  de  Glace  by  Chamonix  ;  its  cascading  end  is  known  as 
the  Glacier  des  Bois.  Another  is  the  neighboring  Glacier  des 
Bossons,  from  whose  upper  amphitheater  a  steep  tongue  descends 
far  below ;  like  the  waterfalls  of  Norway,  the  tongue  may  be 
seen  lying  on  the  side  slope  from  a  considerable  distance  up  or 
down  the  main  valley.  A  third  example  is  the  Glacier  of  the 
Rhone,  whose  splendid  terminal  cascade  is  so  conspicuous  from 
the  road  to  the  Furka  pass.  Possibly  the  Vernagt  glacier  is 
another  of  the  same  kind  ;  its  catastrophic  overflows  into  the 
lower  Rofen  valley  have  often  been  described.  Doubtless  many 
other  examples  of  this  class  might  be  named. 

While  engaged  upon  these  observations  in  the  Alps  in  the 
spring  of  1899,  I  sent  a  brief  note  about  them  to  my  esteemed 
friend,  G.  K.  Gilbert  of  Washington,  telling  him  that  all  the 
lateral  valleys  seemed  to  be  "hung  up  "  above  the  floors  of  the 
trunk  valleys.  His  reply  was  long  in  coming  to  Europe,  and,  on 
arriving  at  last,  it  was  dated  Sitka,  Alaska,  where  Mr.  Gilbert 
had  gone  as  a  member  of  the  Harriman  Alaskan  Expedition, 


652  PHYSIOGRAPHIC  ESSAYS 

and  where  my  note  had  been  forwarded.  He  wrote  that,  for  the 
fortnight  previous  to  hearing  from  me,  he  and  his  companions 
had  been  much  impressed  with  the  discordant  relations  of  lateral 
valleys  over  the  waters  of  the  Alaskan  fiords,  and  he  suggested 
that  such  laterals  should  be  called  "  hanging  valleys,"  —a  term 
which  I  have  since  then  adopted.  He  fully  agreed  that  hanging 
valleys  presented  unanswerable  testimony  for  strong  glacial  ero- 
sion, as  will  be  stated  in  his  forthcoming  report  on  the  geology 
of  the  Expedition. 

After  leaving  Switzerland  I  had  a  brief  view  of  the  lake 
district  in  northwest  England  before  crossing  to  Norway.  The 
amount  of  glacial  erosion  in  the  radiating  valleys  of  the  English 
lakes  has  been  much  discussed,  and,  as  usual,  directly  opposite 
views  have  been  expressed.  Rugged  rocky  knobs  were  seen  in 
abundance  about  Ambleside  and  along  the  ridge  separating  the 
valley  of  Thirlmere  from  St.  John's  Vale  ;  and  the  latter  receives 
a  hanging  valley  from  the  east  near  Dalehead  post  office.  The 
famous  falls  of  Lodore  seemed  to  descend  from  the  mouth  of  a 
hanging  valley  into  Derwentwater.  A  model  of  the  lake  district, 
on  exhibition  at  Keswick,  showed  some  other  examples  of  lateral 
valleys  that  seemed  to  stand  above  the  floors  of  their  main  val- 
leys, notably  one  coming  from  the  south  near  the  northeast  end 
of  Ulleswater.  Since  coming  home  I  read  the  following  in  Marr's 
"  Scientific  Study  of  Scenery  "  : 

We  find  in  the  Lake  District  a  number  of  tributary  valleys  occurring 
in  the  hearts  of  the  ridges,  and  opening  out  far  above  the  bottoms  of  the 
main  valleys,  discharging  their  waters  down  the  slopes  in  cascades.  They 
are  specially  well  marked  on  the  east  side  of  Helvellyn,  and  a  number  of 
them  also  open  into  the  upper  branches  of  Borrowdale. 

The  explanation  is  that  of  Riitimeyer  and  Heim : 

For  a  considerable  period  after  the  deepening  of  the  main  valley,  the 
minor  valleys  will  end  as  definite  gorges  some  height  above  the  floor  of  the 
main  valley,  and  discharge  their  waters  in  a  series  of  cascades  or  falls 
down  the  side  of  the  main  valley  (136). 

One  of  my  former  students,  Mr.  W.  B.  Lloyd,  has  recently 
shown  me  a  number  of  photographs  of  the  fiords  of  southern 
New  Zealand,  which  he  brought  back  from  a  visit  to  that  distant 


GLACIAL  EROSION  653 

country.  High  cascades,  plunging  from  hanging  lateral  valleys 
into  the  broad  waters  of  the  fiords,  are  repeatedly  shown. 

Fiords  and  Hanging  Valleys  in  Norway.  In  Norway  I  had 
the  pleasure  of  making  a  ten  days'  cross-country  excursion  in 
company  with  Dr.  Reusch,  director  of  the  Norwegian  Geological 
Survey.  We  entered  from  Bergen  through  Hardanger  fiord,  and 
crossed  the  highlands  by  the  Haukelisaetr  road  to  Skien  on  the 
southeastern  lowlands,  thus  making  a  general  cross  section  on 
which  many  characteristic  features  were  seen.  Norway  has  long 
been  known  as  a  land  of  waterfalls,  but  it  is  not  generally  stated 
with  sufficient  clearness  or  emphasis  that  many  or  most  of  the 
falls  are  formed  by  the  descent  of  streams  from  maturely  opened 
trough-like  hanging  valleys  which  are  abruptly  cut  off  by  the 
walls  of  the  fiords.  The  discordance  between  main  and  side 
streams  is  simply  amazing.  The  fiord  valleys  are  frequently  one 
or  two  miles  wide  ;  the  waters  of  the  fiords  are  of  great  depths, 
reaching  three  thousand  feet  in  some  cases.  Even  when  a  side 
valley  stands  but  little  above  sea-level,  its  floor  may  be  half  a 
mile  above  the  floor  of  the  fiord.  On  passing  inland  beyond  the 
head  of  the  fiord  water,  where  the  whole  depth  of  the  fiord  val- 
ley is  visible,  the  side  valleys  may  open  more  than  a  thousand 
feet  above  the  main-valley  floor.  In  many  cases  where  the  fiords 
are  inclosed  by  smooth  walls,  the  cascading  side  streams  have 
not  yet  incised  a  cleft  in  the  bare  rock  surface,  so  that  their 
foaming  waters  are  visible  for  many  miles  up  and  down  the 
fiord.  Streams  of  considerable  size  somtimes  plunge  down  from 
the  rolling  uplands  in  whose  edge  they  seem  to  have  just  begun 
to  cut  a  cleft.  Abnormal  discordance  of  trunk  and  branch 
stream  is,  therefore,  a  strongly  marked  characteristic  of  the 
Norwegian  drainage.  The  necessity  for  appealing  to  strong 
glacial  erosion  in  explanation  of  this  prevailing  discordance 
may  be  set  forth  as  follows: 

Measure  of  Glacial  Erosion  in  Norwegian  Fiords.  The  deep 
valleys  of  Norway,  partly  occupied  by  sea  water,  are  incised 
beneath  an  uneven  highland  which  bears  so  many  hills  and 
mountains  that  it  makes  little  approach  to  a  peneplain,  yet 
which  here  and  there  shows  so  many  broadly  opened  uplands  be- 
tween the  hills  and  mountains  that  it  may  be  taken  to  represent 


654  PHYSIOGRAPHIC  ESSAYS 

the  well-advanced  work  of  a  former  cycle  of  denudation  when 
the  region  stood  much  lower  than  it  stands  now.  As  a  whole 
a  mature  or  late-mature  stage  seems  to  have  been  reached 
before  a  movement  of  uplift  introduced  the  present  cycle.  Let 
us  now  make  two  suppositions  regarding  the  work  of  normal 
river  erosion  in  the  pre-glacial  part  of  the  present  cycle,  in 
order  to  determine,  if  possible,  how  much  additional  erosion 
must  be  attributed  to  ice  in  the  production  of  existing  forms. 

First,  let  it  be  supposed  that  the  revived  main  rivers  had 
incised  their  valleys  to  the  depth  of  the  present  fiords  in  pre- 
glacial  time,  and  that  the  discordance  of  main  and  side  valleys 
now  visible  is  the  appropriate  result  of  the  youth  of  the  present 
cycle.  If  we  recall  only  the  steepness  of  the  fiord  walls,  this 
supposition  might  be  justified,  and  thus  the  amount  of  glacial 
erosion  needed  to  develop  existing  forms  would  be  small.  But 
it  must  not  be  forgotten  that  the  fiords,  although  often  steep- 
walled,  are  always  broad,  much  broader  than  a  young  pre-glacial 
valley  could  have  been  at  that  stage  of  early  youth  when  its 
side  streams  had  not  cut  down  to  its  own  depth.  Hence  glacial 
erosion  must,  under  this  supposition,  be  appealed  to  for  the 
widening  of  pre-glacial  canons,  steep-walled  and  narrow,  into  the 
existing  fiord  troughs,  steep-walled  and  broad.  At  the  middle 
of  the  fiord  troughs  the  lateral  erosion  thus  demanded  would 
often  measure  thousands  of  feet,  and  that  in  the  most  massive 
and  resistant  crystalline  rocks. 

A  second  supposition  leads  to  no  greater  economy  of  glacial 
action.  Let  it  be  supposed  that  the  revived  streams  of  pre- 
glacial  time  had  reached  maturity  before  the  advent  of  the  gla- 
cial period.  In  that  case  the  side  streams  must  have  entered 
the  main  streams  at  accordant  grade,  and  hence  the  main  valleys 
could  not  then  have  been  cut  much  deeper  than  the  side  valleys 
are  now  cut ;  not  so  deep,  indeed,  for  the  side  valleys  have 
been  somewhat  deepened  by  glacial  action,  if  one  may  judge  by 
their  trough-like  form  as  well  as  by  the  evidence  of  intense  gla- 
cial action  all  over  the  uplands,  even  over  most  of  the  surmounting 
hills  and  mountains.  Hence,  to  develop  the  existing  discordant 
valley  system  from  a  mature  pre-glacial  valley  system  of  normal 
river  erosion  requires  a  great  deepening  of  the  fiords  by  ice 


GLACIAL  EROSION  655 

action,  again  to  be  measured  in  thousands  of  feet.  Thus  there 
seems  to  be  no  escape  from  the  conclusion  that  glacial  erosion 
has  profoundly  modified  Norwegian  topography.  As  far  as  I 
could  judge  from  my  brief  excursion  over  the  highlands,  either 
one  of  the  two  suppositions  above  considered  is  permissible, 
provided  only  that  strong  glacial  erosion  comes  after  the  river 
work  of  the  current  cycle. 

If  the  Hardanger  fiord  may  be  taken  as  the  type  of  its  many 
fellows,  one  may  say  that  hanging  lateral  valleys  are  the  rule, 
not  the  exception,  in  Norway.  Furthermore,  the  smoothed, 
spurless  walls  of  the  larger  fiords,  composed  of  firm,  bare  rock 
from  the  upland  to  water  edge,  do  not  resemble  the  ravined  and 
buttressed  sides  of  normal  valleys.  The  marks  of  downward 
water  erosion  are  replaced  by  what  seem  to  be  marks  of  nearly 
horizontal  plucking  and  scouring.  Blunt-headed  valleys  and  cor- 
ries  (botner)  both  seem  beyond  production  by  normal  weathering 
and  washing.  Yet,  striking  as  these  features  are,  they  do  not 
seem  to  me  so  compulsory  of  a  belief  in  strong  glacial  erosion 
as  the  hanging  valleys  that  have  so  little  relation  to  the  fiords 
beneath  them,  and  the  flaunting  waterfalls  that  descend  so 
visibly  from  the  hanging  valleys,  instead  of  retiring,  as  is  the 
habit  of  falls  all  over  the  unglaciated  parts  of  the  world,  into 
ravines  where  they  are  hid  to  sight  from  most  points  of  view. 

The  rocky  islands  that  rise  from  the  shallower  parts  of  the 
fiords  should  not  be  taken  as  signs  of  feeble  glacial  erosion,  but 
rather  as  remnants  surviving  from  the  destruction  of  larger 
masses  in  virtue  of  some  slight  excess  of  resistance.  A  well- 
known  example  of  this  kind  is  near  Odde  at  the  head  of  the 
large  southern  arm  (Sorfjord)  of  the  upper  Hardanger  fiord  ; 
but  in  the  same  neighborhood  are  several  fine  hanging  valleys, 
one  of  which  has  its  open  floor  high  above  the  fiord  level ; 
its  cascading  stream,  the  Strandfos,  descends  into  Sandven 
lake,  Just  south  of  the  side  valley  occupied  by  the  well-known 
Buer  glacier. 

Correlation  of  River  Valleys  and  Glacier  Valleys.  Thus  far 
the  consequences  of  glacial  erosion  have  been  described  as  if 
they  were  unlike  those  of  river  erosion,  especially  in  respect  to 
the  production  of  hanging  valleys.  A  just  comparison  of.  the 


656  PHYSIOGRAPHIC  ESSAYS 

two  agencies  will  show  that  their  resemblances  are  more  marked 
than  their  differences,  when  due  allowance  is  made  for  their 
individual  peculiarities. 

The  likeness  of  glaciers  and  rivers  has  been  frequently  con- 
sidered. The  motion  of  water  streams  and  ice  streams  is  retarded 
by  bottom  and  banks,  and  is  fastest  in  mid-channel  where  farthest 
removed  from  all  hindrances.  The  motion  is  faster  on  strong 
than  on  gentle  slopes,  and  in  large  than  in  small  streams  ;  the 
line  of  fastest  motion  departs  from  the  medial  axis  towards  the 
concave  bank.  Forel  (204)  and  Gannett  (422)  have  justly  com- 
pared ordinary  valley  glaciers,  not  to  rivers  that  mouth  in  the 
sea,  but  to  rivers  that  descend  from  mountains  to  wither  away 
on  piedmont  deserts.  The  terminal  moraine  of  the  glacier  cor- 
responds to  the  terminal  delta-like  fan  of  withering  rivers.  The 
fluctuation  of  a  withering  river  following  changes  of  weather  or 
season  corresponds  to  the  secular  fluctuations  of  glaciers,  as 
during  the  period  of  about  thirty-five  years  in  the  Alps.  The 
advance  and  retreat  at  the  end  of  large  glaciers  does  not  occur 
synchronously  with  the  advance  and  retreat  of  small  glaciers, 
although  both  large  and  small  glaciers  accomplish  their  periodic 
variations  of  length  in  the  same  interval ;  and  it  is  probable  that 
the  same  contrast  obtains  in  withering  rivers  of  different  length, 
although  I  cannot  find  any  direct  statements  to  this  effect. 
Meunier  (1043)  nas  suggested  that  certain  peculiar  successions 
of  drift  deposits  in  Switzerland  may  be  the  result  of  the  enlarge- 
ment of  the  drift-bringing  glacier  by  the  capture  of  the  head 
reservoirs  of  another  glacier,  after  the  analogy  of  rivers.  Gan- 
nett and  Penck  (see  abstracts  below)  have  gone  further  still 
and  have  shown  that  the  hanging  valleys,  so  characteristic  of 
strongly  glaciated  drainage  systems,  have  a  perfect  analogy  in 
the  valley  systems  of  ordinary  rivers  in  non-glaciated  areas.  This 
comparison  is  so  instructive  that  it  deserves  full  statement  here. 

The  "nice  adjustment  of  declivities"  that  characterizes  the 
main  and  the  side  valleys  of  a  river  system  is  found  only  in 
maturely  developed  valleys.  The  adjustment  or  accordance  be- 
tween main  trunk  and  lateral  branch  obtains  only  with  respect 
to  the  surface  of  the  streams  or  to  the  floor  of  their  val- 
leys. The  beds  of  the  trunk  and  the  branch  channels  may  be 


GLACIAL  EROSION  657 

discordant  at  their  junction,  and  this  discordance  will  increase 
with  the  difference  in  volume  of  trunk  and  branch  stream. 
Truly,  the  discordance  of  stream  beds  is  seldom  noted,  because 
the  beds  are  hidden  by  the  streams ;  but  if  a  river  system  were 
laid  dry,  we  may  be  assured  that  the  beds  of  the  smaller  tribu- 
taries would  open  in  the  banks  of  the  main  river  a  number  of 
feet  from  its  bottom.  In  the  case  of  the  Mississippi,  the  dis- 
cordance might  easily  measure  fifty  or  more  feet. 

All  this  applies  equally  to  glacial  streams.  The  surface  of  a 
tributary  glacier  is  adjusted  to  the  surface  of  the  trunk  glacier 
that  it  joins  ;  but  the  depth  of  the  beds  may  be  very  different. 
As  long  as  the  glaciers  occupy  their  channels,  the  discordance 
of  their  beds  may  not  be  often  considered,  but  when  a  climatic 
change  causes  the  glaciers  to  melt  away,  their  channels  are 
called  valleys,  and  the  discordance  of  main  and  lateral  glaciated 
valley  floors  is  taken  as  an  abnormal  feature.  In  reality  the 
discordance  is  perfectly  normal  to  the  peculiar  system  of  ice 
drainage  by  which  it  was  produced,  however  discordant  it  may 
be  to  the  system  of  water  drainage  now  in  possession  of  the 
valleys.  Let  us  compare  the  maturely  developed  channels  of 
rivers  and  glaciers. 

Channels  of  Mature  Rivers  and  Glaciers.  A  river  flows  rap- 
idly, and  the  cross  section  of  its  channel  is  but  a  small  fraction 
of  the  cross  section  of  its  valley.  The  river  channel  is  U-shaped, 
very  broad  compared  to  its  depth,  while  the  valley  sides  flare 
open,  V-like,  above  the  river  banks.  The  water  surface  slopes 
steadily  downstream,  but  the  channel  bed  has  many  small  in- 
equalities in  the  form  of  bars  and  basins,  and  the  water  in  the 
bottom  of  the  basins  must  ascend  a  little  to  get  out  of  them.  If 
the  river  should  dry  away,  the  deeper  parts  of  the  bed  would 
be  occupied  by  pools  of  standing  water,  while  the  bars  would 
show  lines  suggestive  of  flowing  water.  The  banks  of  the  river 
channel  are  smoothly  worn  in  nearly  horizontal  lines,  parallel  to 
the  flow  of  the  river  current,  while  the  sloping  sides  of  a  river 
valley  are  buttressed  with  spurs  and  scored  by  the  downhill 
ravines  of  descending  streams.  At  the  junction  of  trunk  and 
branch  streams  a  moderate  discordance  in  the  level  of  the 
channel  beds  is  to  be  expected,  but  this  is  seldom  considered 


658  PHYSIOGRAPHIC  ESSAYS 

because  the  channels  are  usually  occupied  by  water  and  the 
beds  are  hidden. 

A  glacier  moves  slowly,  and  the  cross  section  of  its  channel 
may  be  a  considerable  part  of  the  cross  section  of  the  valley 
that  it  drains.  Forel  estimates  that  the  glacier  of  the  Rhone, 
even  where  descending  its  steep  cascade,  has  only  i :  12,000,000 
of  the  velocity  of  a  large  river  on  a  similar  slope  (203).  The 
glacial  channel  is  U-shaped,  broad  and  deep,  while  the  valley 
flares  open,  V-like,  above  the  ice  surface.  The  ice  surface  slopes 
steadily  downstream,  but  the  bed  of  its  channel  is  unevenly 
scoured,  here  rising  in  knobs,  there  sinking  in  hollows  or  basins 
from  which  the  bottom  ice  must  ascend  a  little  as  it  moves  for- 
ward. When  the  ice  melts  away,  lakes  occupy  the  rock  basins ; 
the  rocky  knobs  are  seen  to  be  rounded  and  plucked  in  a  man- 
ner suggestive  of  heavily  moving  ice.  The  banks  of  the  channel 
are  scoured  and  fluted  parallel  to  the  ice  motion,  but  above  the 
ice-worn  channel  the  flaring  valley  sides  are  ravined  by  de.scend- 
ing  water  streams.  At  the  junction  of  trunk  and  branch  glaciers 
a  strong  discordance  in  the  level  of  the  channel  beds  may  be 
expected;  and  the  discordance  becomes -conspicuous  when  the 
glaciers  melt  away  and  leave  their  " channels"  to  be  called 
"valleys."  Hanging  side  valleys  are  therefore  appropriate  as 
well  as  characteristic  features  of  glaciated  main  valleys.  They 
must  come  to  be  considered  even  more  significant  of  glacial 
erosion  than  lake  basins. 

The  Cycle  of  Glacial  Denudation.  The  points  of  resemblance 
between  rivers  and  glaciers,  streams  of  water  and  streams  of 
ice,  are  so  numerous  that  they  may  be  reasonably  extended  all 
through  a  cycle  of  denudation.  Let  us  then  inquire  if  glaciers 
may  not,  during  their  ideal  life  history,  develop  as  orderly  a  suc- 
cession of  features  as  that  which  so  well  characterizes  the  normal 
development  of  rivers.  The  "life  history  of  a  glacier"  need  not 
be  taken  only  in  the  sense  so  well  illustrated  in  the  last  chapter 
of  Russell's  "Glaciers  of  North  America,"  where  the  glacier  is 
called  young  when  it  is  small  at  the  beginning  of  a  glacial  cli- 
matic epoch,  mature  when  it  is  largest  during  the  full  establish- 
ment of  the  glacial  climate,  and  old  when  it  is  vanishing  under 
the  reestablish  men  t  of  a  milder  climate.  Let  us  here  consider 


GLACIAL  EROSION  659 

the  life  history  of  a  glacier  under  a  constant  glacial  climate, 
from  the  beginning  to  the  end  of  a  cycle  of  denudation,  just  as 
Russell  has  considered  the  "life  history  of  a  river"  under  a  con- 
stant pluvial  climate,  in  his  "  Rivers  of  North  America."  Thus 
young  glaciers  will  be  those  which  have  been  just  established  in 
courses  that  are  consequent  upon  the  slopes  of  a  newly  uplifted 
land  surface ;  mature  glaciers  will  be  those  which  have  eroded 
their  valleys  to  grade  and  thus  dissected  the  uplifted  surface ; 
and  old  glaciers  will  be  those  which  cloak  the  whole  lowland  to 
which  the  upland  has  been  reduced,  or  which  are  slowly  fading 
in  the  milder  climate  of  the  low  levels  appropriate  to  the  close 
of  the  cycle  of  denudation. 

Imagine  an  initial  land  surface  raised  to  a  height  of  several 
thousand  feet,  with  a  moderate  variety  of  relief  due  to  deforma- 
tion. Let  the  snow  line  stand  at  a  height  of  two  hundred  feet. 
As  elevation  progresses,  snow  accumulates  on  all  the  upland 
and  highland  surfaces.  Glaciers  are  developed  in  every  basin 
and  trough ;  they  creep  slowly  forward  to  lower  ground,  where 
they  enter  a  milder  climate  (or  the  sea)  and  gradually  melt  away. 
At  some  point  between  its  upper  heads  and  its  lower  end,  each 
glacier  will  have  a  maximum  volume.  Downstream  from  this 
point  the  glacier  will  diminish  in  size,  partly  by  evaporation  but 
more  by  melting,  and  the  ice  water  thus  provided  will  flow 
away  from  the  end  of  the  glacier  in  the  form  of  an  ordinary 
stream,  carving  its  valley  in  normal  fashion.  Some  erosion  may 
be  accomplished  under  the  upper  fields  of  snow  and  neve,  but 
it  is  believed  that  more  destructive  work  is  done  beneath  the 
ice.  The  erosion  is  accomplished  by  weathering,  scouring,  pluck- 
ing, and  corrading.  Weathering  occurs  where  variations  of  ex- 
ternal temperature  penetrate  to  the  bed  rock,  as  is  particularly 
the  case  between  the  seracs  of  glacial  cascades,  and  again  along 
the  line  of  deep  crevasses,  or  hergschrunds,  that  are  usually 
formed  around  the  base  of  reservoir  walls,  which  are  thus 
transformed  into  corries  (cirques,  karen,  botner),  as  has  ,  been 
suggested  by  several  observers  ;  scouring  is  the  work  of  rock 
waste  dragged  along  beneath  the  glacier,  by  which  the  bed  rock 
is  ground  down,  striated,  and  smoothed  ;  plucking  results  from 
friction  under  long-lasting  heavy  pressure,  by  which  blocks  of 


660  PHYSIOGRAPHIC  ESSAYS 

rock  are  removed  bodily  from  the  glacier  bed  and  banks ;  cor- 
rading  is  the  work  of  sub-glacial  streams,  which  must  be  well 
charged  with  tools,  large  and  small,  and  which  must  often  flow 
under  heavy  pressure  and  with  great  energy.  All  these  proc- 
esses are  here  taken  together  as  " glacial  erosion.' 

Let  it  be  assumed  that  at  first  the  slope  of  a  glacier's  path 
was  steep  enough  to  cause  it  to  erode  for  the  greater  part  or  for 
the  whole  of  its  length.  It  is  to  be  understood  that  a  valley  in- 
cludes the  channel  that  is  eroded  along  its  floor.  The  channel, 
with  its  beds  and  banks,  is  therefore  that  part  of  a  valley  which 
is,  occupied  by  the  stream.  Each  young  glacier  will  then  pro- 
ceed to  cut  down  its  consequent  valley  at  a  rate  dependent  on 
various  factors,  such  as  depth  and  velocity  of  ice  stream,  char- 
acter of  rock  bed,  quantity  of  ice-dragged  waste,  and  so  on;  and 
the  eroded  channel  in  the  bottom  of  the  valley  will  in  time  be 
given  a  depth  and  width  that  will  better  suit  the  needs  of  ice 
discharge  than  did  the  initial  basin  or  trough  of  the  uplifted  sur- 
face. The  upper  slopes  of  the  glacial  stream  will  thus  be  steep- 
ened, while  its  lower  course  will  be  given  a  gentler  descent. 
Owing  to  the  diminution  of  the  glacier  toward  its  lower  end, 
the  channel  occupied  by  it  will  diminish  in  depth  and  breadth 
downwards  from  the  point  of  maximum  volume,  this  being 
analogous  to  the  decrease  in  the  size  of  the  channel  of  a  wither- 
ing river  below  the  point  of  its  maximum  volume.  A  time  will 
come  when  all  the  energy  of  the  glacier  on  its  gentler  slope  will 
be  fully  taxed  in  moving  forward  the  waste  that  has  been 
brought  down  from  the  steeper  slopes ;  then  the  glacier  be- 
comes only  a  transporting  agent,  not  an  eroding  agent,  in  its 
lower  course.  This  condition  will  be  first  reached  near  the  lower 
end,  and  slowly  propagated  headwards.  Every  part  of  the  glacier 
in  which  the  balance  between  ability  to  do  work  and  work  to  be 
done  is  thus  struck  may  be  said  to  be  "graded";  and  in  all  such 
parts  the  surface  of  the  glacier  will  have  a  smoothly  descending 
slope.  Maturity  will  be  reached  when,  as  in  the  analogous  case 
of  a  river,  the  nice  adjustment  between  ability  and  work  is 
extended  to  all  parts  of  a  glacial  system.  In  the  process  of 
developing  this  adjustment  a  large  trunk  glacier  might  en- 
trench the  main  valley  more  rapidly  than  one  of  the  smaller 


GLACIAL  EROSION  66 1 

branches  could  entrench  its  side  valley ;  then  for  a  time  the 
branch  would  join  the  trunk  in  an  ice  rapid  of  many  seracs. 
But  when  the  trunk  glacier  had  deepened  its  valley  so  far  that 
further  deepening  became  slow,  the  branch  glacier  would  have 
opportunity  to  erode  its  side  valley  to  an  appropriate  depth, 
and  thus  to  develop  an  accordant  junction  of  trunk  and  branch 
ice  surfaces,  although  the  channels  of  the  larger  and  the  smaller 
streams  might  still  be  of  very  unequal  depth,  and  the  channel 
beds  might  stand  at  discordant  levels.  If  the  glaciers  should 
disappear  at  this  stage  of  the  cycle,  their  channels  would  be 
called  valleys,  and  the  discordance  of  the  channel  beds  might 
naturally  excite  surprise.  The  few  observers  who,  previous  to 
1898,  commented  upon  a  discordance  of  this  kind  explained  it 
as  a  result  of  excessive  erosion  of  the  main  valley  by  the  trunk 
glacier,  while  the  hanging  lateral  valleys  were  implicitly,  if 
not  explicitly,  regarded  as  hardly  changed  from  their  pre- 
glacial  form. 

When  the  trunk  and  branch  glaciers  have  developed  well- 
defined,  maturely  graded  valleys,  the  continuous  snow  mantle 
that  covered  the  initial  uplands  of  early  youth  is  exchanged  for 
a  discontinuous  cover,  rent  on  the  steep  valley  sides  where 
weathering  comes  to  have  a  greatly  increased  value,  and  thick- 
ened where  the  ice  streams  have  established  their  courses.  This 
change  corresponds  to  that  between  the  ill-defined  initial  drain- 
age in  the  early  youth  and  the  well-defined  drainage  in  the 
maturity,  of  the  river  cycle. 

It  is  probable  that  variations  in  rock  structure  will  have  per- 
mitted a  more  rapid  development  of  the  graded  condition  in  one 
part  of  the  glacial  valley  than  in  another,  as  is  the  case  with 
rivers  of  water.  Steady-flowing  reaches  and  broken  rapids  will 
thus  be  produced  in  the  ice  stream  during  its  youth ;  and  the 
glacial  channel  may  then  be  described  as  "  broken-bedded." 
But  all  the  rapids  must  be  worn  down  and  all  the  reaches  must 
become  confluent  in  maturity.  It  is  eminently  possible  that  the 
reaches  on  the  weaker  or  more  jointed  rocks  may  be  eroded 
during  youth  to  a  somewhat  greater  depth  than  the  sill  of  more 
resistant  or  less  jointed  rock  next  downstream ;  and  if  the  gla- 
cier should  vanish  by  climatic  change  while  in  this  condition,  a 


662  PHYSIOGRAPHIC  ESSAYS 

lake  would  occupy  the  deepened  reach,  while  the  lake  outlet 
would  flow  forward  over  rocky  ledges  to  the  next  lower  reach 
or  lake.  Many  Norwegian  valleys  to-day  seem  to  be  in  this  con- 
dition. Indeed,  some  observers  have  described  broken-bedded 
valleys  as  the  normal  product  of  glacial  erosion,  without  refer- 
ence to  the  early  stage  in  the  glacial  cycle  of  which  broken- 
bedded  glacial  channels  seem  to  be  characteristic.  Truly,  it  is 
not  always  explicitly  stated  that  the  resistance  of  the  rock  bed 
varies  appropriately  to  the  change  of  form  in  a  broken-bedded 
channel,  but  the  variations  of  structural  resistance  or  firmness 
that  the  searching  pressure  and  friction  of  a  heavy  glacier  could 
detect  might  .be  hardly  recognizable  to  our  superficial  observa- 
tions ;  and,  on  the  other  hand,  the  analogy  of  young  ungraded 
glaciers  with  young  ungraded  rivers  seems  so  natural  and  reason- 
able that  broken-bedded  glacial  channels  ought  to  be  regarded 
only  as  features  of  young  glacial  action,  not  as  persistent  fea- 
tures always  to  be  associated  with  glacial  erosion.  If  the  glaciers 
had  endured  longer  in  channels  of  this  kind,  the  ''rapids"  and 
other  inequalities  by  which  the  bed  may  be  interrupted  must 
have  been  worn  back  and  lowered,  and  in  time  destroyed. 

If  a  young  glacier  erodes  its  valley  across  rocks  of  distinctly 
different  resistances,  a  strong  inequality  of  channel  bed  may  be 
developed.  Basins  of  a  considerable  depth  may  be  excavated  in 
the  weaker  strata,  while  the  harder  rocks  are  less  eroded  and 
cross  the  valleys  in  rugged  sills.  Forms  of  this  kind  are  known 
in  Alpine  valleys  ;  for  example,  in  the  valley  of  the  Aar  above 
Meiringen  (Wallace,  b,  176)  and  in  the  lower  Gasternthal  near  its 
junction  with  the  Kanderthal ;  in  both  these  cases  the  basins 
have  been  aggraded  and  the  sills  have  been  trenched  by  the 
post-glacial  streams.  In  the  lower  Gasternthal  the  height  and 
steepness  of  the  rocky  sill,  when  approached  from  upstream,  is 
astonishing ;  its  contrast  to  the  basin  that  it  incloses  is  difficult 
enough  to  explain  even  for  those  who  are  willing  to  accept 
strong  glacial  erosion.  It  should,  however,  6e  noted  that  river 
channels  also  are  deeper  in  the  weaker  rocks  upstream  from  a 
hard  rock  sill ;  if  the  river  volume  should  greatly  decrease,  a 
small  lake  would  remain  above  the  sill,  drained  by  a  slender 
stream  cutting  a  gorge  through  the  sill. 


GLACIAL  EROSION  663 

If  an  initial  depression  occurred  on  the  path  of  the  glacier,  so 
deep  that  the  motion  of  the  ice  through  it  was  much  retarded, 
an  ice  lake  would  gather  in  it.  Then  the  waste  dragged  into  the 
basin  from  upstream  might  accumulate  upon  its  floor  until  the 
depth  of  the  basin  was  sufficiently  decreased  and  the  velocity  of 
the  ice  through  it  sufficiently  increased  to  bring  about  a  balance 
between  ability  to  do  work  and  work  to  be  done.  Here  the 
maturely  graded  condition  of  the  ice  stream  would  have  been 
attained  by  aggrading  its  bed  instead  of  degrading  it ;  this 
being  agarn  closely  analogous  to  the  case  of  a  river  which 
aggrades  initial  depressions  and  degrades  initial  elevations  in 
producing  its  maturely  graded  course. 

Water  streams  subdivide  toward  the  headwaters  into  a  great 
number  of  very  fine  rills,  each  of  which  may  retrogressively  cut 
its  own  ravine  in  a  steep  surface,  not  cloaked  by  waste.  But  the 
branches  of  a  glacial  drainage  system  are  much  more  clumsy, 
and  the  channels  that  they  cut  back  into  the  upland  or  mountain 
mass  are  round-headed  or  amphitheater-like ;  but  the  beds  of 
the  branching  glaciers  cannot  be  cut  as  deep  as  the  bed  of  the 
large  glacial  channel  into  which  they  flow ;  thus  corries,  perched 
on  the  side  walls  of  large  valleys,  may  be  produced  in  increasing 
number  and  strength  as  glacial  maturity  approaches,  ?>nd  in  de- 
creasing strength  and  number  as  maturity  passes  into  old  age. 
As  maturity  approaches,  the  glacial  system  will  include  n°tJfc|y 
those  branches  that  are  consequent  upon  the  initial  form^but 
certain  others  which  have  come  into  existence  by  the  headward 
erosion  of  their  nev6  reservoirs  following  the  guidance  of  weak 
structures ;  thus  a  maturely  developed  glacial  drainage  system 
may  have  its  subsequent  as  well  as  its  consequent  branches.  It 
is  entirely  conceivable,  as  has  been  suggested  by  Meunier,  that 
one  ice  stream  may  capture  the  upper  part  of  another.  The  con- 
ditions most  favorable  for  such  a  process  resemble  those  under 
which  river  diversions  and  adjustments  take  place,  namely,  a 
considerable  initial  altitude  of  the  region,  allowing  a  deep  dis- 
section ;•  a  significant  difference  of  drainage  areas  or  of  slopes, 
whereby  certain  glaciers  incise  deeper  valleys  than  others ;  a 
considerable  diversity  of  mountain  structure,  permitting  such 
growth  and  arrangement  of  subsequent  glaciers  as  shall  bring 


664  PHYSIOGRAPHIC  ESSAYS 

the  head  reservoir  of  a  subsequent  ice  stream  alongside  of  and 
somewhat  beneath  the  banks  of  a  consequent  ice  stream.  Thus 
glacial  systems  may  come  to  adjust  their  streams  to  the  struc- 
tures upon  which  they  work,  just  as  happens  in  river  systems. 

The  load  transported  by  a  glacial  system  may  at  first  be  sup- 
plied largely  by  waste  plucked  and  scoured  from  the  beds  of  the 
glacial  channels  as  well  as  by  waste  detached  from  the  inclos- 
ing slopes ;  but  in  time,  when  the  graded  condition  of  the  chief 
channels  is  reached  and  their  further  deepening  almost  ceases, 
by  far  the  largest  share  of  load  will  be  supplied  from  the  sub- 
aerial  valley  sides,  where  weathering  of  the  ordinary  kind  will 
ravine  the  slopes,  thus  producing  a  topography  that  is  strongly 
contrasted  with  the  smooth  walls  of  the  glacial  channels.  If  the 
initial  glacial  system  should  incise  its  channels  so  deeply  beneath 
a  lofty  highland  that  the  supply  of  waste  from  the  valley  sides 
continued  to  increase  after  the  development  of  graded  glacial 
channels,  it  is  conceivable  that  the  channel  beds  might  have  to 
be  aggraded  for  a  time,  as  is  believed  to  be  the  case  with  river 
channels  under  similar  conditions  ;  but  owing  to  the  receipt  on 
the  glacial  surface  of  waste  from  the  valley  sides,  it  is  also  con- 
ceivable that  this  analogy  may  not  closely  obtain.  Toward  the 
end  of  the  ice  stream  it  may  well  happen  that  the  diminution  of 
its  volume  and  the  consequent  diminution  of  its  capacity  to  do 
work  will  result  in  the  aggradation  of  its  bed  by  waste  that  can- 
not be  carried  farther  forward.  At  the  same  time,  the  outflowing 
river  may  be  unable  to  wash  away  all  the  waste  that  is  delivered 
to  it,  and  so,  for  a  time  through  later  youth  and  early  maturity, 
the  river  may  act  as  an  aggrading  agent  and  build  up  a  broad, 
flat  alluvial  fan,  such  as  fronts  the  terminal  moraines  of  the 
Alpine  glaciers  that  once  descended  to  the  plain  of  Lombardy. 
Some  response  to  the  change  thus  produced  in  the  altitude  of 
the  end  of  the  glacier  may  be  expected  far  up  its  channel,  whose 
bed  would  thus  come  to  be  aggraded  with  till.  Similarly,  the  ice 
sheets  that  spread  from  the  Scandinavian  and  Laurentian  high- 
lands over  the  lowlands  on  the  south  changed  their  .behavior 
from  degrading  agents  in  the  central  area  to  aggrading  agents 
on  the  peripheral  area.  Hence,  a  belief  in  effective  erosion  is 
not  antagonistic  to  a  belief  in  effective  deposition  in  the  case  of 


GLACIAL  EROSION  665 

glaciers  any  more  than  in  the  case  of  rivers.  In  each  case  the 
action  varies  appropriately  to  its  place  in  the  drainage  system 
and  to  its  stage  in  the  cycle.  But  there  will  be  a  later  stage, 
when  the  wasting  of  the  superglacial  slopes  reduces  them  to 
moderate  declivity,  so  that  the  waste  delivered  from  them 
decreases  in  quantity ;  then  the  outflowing  water  stream  at  the 
end  of  the  glacier  may  become  a  degrading  agent ;  the  altitude 
of  the  end  of  the  glacier  may  be  slowly  lessened;  and  a  very 
slow  and  long-continued  deepening  of  the  whole  glacial  channel 
will  take  place,  without  requiring  a  departure  from  an  essen- 
tially graded  condition. 

As  the  general  denudation  of  the  region  progresses,  the  snow 
fall  must  be  decreased  and  the  glacial  system  must  shrink  some- 
what, leaving  a  greater  area  of  lowland  surface  to  ordinary  river 
drainage.  When  the  upland  surface  is  so  far  destroyed  that 
even  the  hill-tops  stand  below  the  2OO-foot  contour,  the  snow 
fields  will  be  represented  only  by  the  winter  snow  sheet,  and 
the  glaciers  will  have  disappeared,  leaving  normal  agencies  to 
complete  the  work  of  denudation  that  they  have  so  well  begun. 

If  a  snow  line  at  sea-level  be  assumed,  glaciation  would  per- 
sist even  after  the  land  had  been  worn  to  a  submarine  plain  of 
denudation  at  an  undetermined  depth  beneath  sea-level.  The 
South  Polar  regions  offer  a  suitable  field  for  the  occurrence  of 
such  a  surface. 

Whether  glaciers  of  the  Norwegian  or  of  the  Alpine  type  shall 
occur  is  dependent  partly  on  initial  conditions,  partly  on  the 
stage  of  advance  through  the  cycle  of  denudation.  If  the  initial 
form  offer  broad  uplands,  separated  by  deep  valleys,  snow  fields 
of  the  Norwegian  type  may  have  possession  of  the  uplands  dur- 
ing the  youth  of  the  glacial  cycle  ;  but  when  maturity  is  reached, 
the  uplands  will  be  dissected,  and  the  original  confluent  snow 
field  will  be  resolved  into  a  number  of  head  reservoirs,  separated 
by  ridges.  On  the  other  hand,  as  the  later  stages  of  the  cycle 
are  approached,  the  barriers  between  adjacent  reservoirs  will  be 
worn  away,  and  they  will  tend  to  become  confluent,  here  and 
there  broken  only  by  Nunatuker.  If  the  snow  line  lay  low 
enough,  a  completely  confluent  ice  and  snow  shield  would  cover 
the  lowland  of  glacial  denudation  when  old  age  had  been  reached. 


666  PHYSIOGRAPHIC  ESSAYS 

If  the  glacial  conditions  of  Greenland  preceded  as  long  as  they 
have  followed  the  glacial  period  over  the  rest  of  the  North 
Atlantic  region,  who  can  say  how  far  the  ice  of  the  Greenland 
shield  has  modified  the  forms  on  which  its  work  began ! 

Glacial  Distributaries,  If  a  maturely  dissected  mountain  range 
were  occupied  by  snow  fields  and  glaciers  of  large  size,  certain 
peculiar  results  might  be  expected  near  the  mountain  base.  Under 
normal  pre-glacial  conditions  a  small,  low  ridge  suffices  for  the 
complete  separation  of  two  river  systems,  because  the  channels 
of  rivers  are  so  small  in  comparison  to  their  valleys.  But  glacial 
channels  are  a  large  part  of  their  valleys,  and  when  great  glaciers 
from  the  lofty  mountain  centers  descend  by  the  master  valleys 
to  the  mountain  flanks  or  even  to  the  piedmont  plains,  distribu- 
tary ice  streams  or  outflowing  branches  may  naturally  enough  be 
given  off  wherever  the  ice  surface  rises  high  enough  to  overtop 
the  ridges  by  which  the  master  valleys  are  separated  from  ad- 
jacent minor  valleys.  If  a  distributary  branch  has  sufficient 
strength  and  endurance,  it  may  wear  down  the  ridge  that  it 
crosses  and  thus  increase  and  perpetuate  its  lateral  discharge  ; 
but  it  cannot  usually  be  expected  to  erode  a  channel  as  deep  as 
that  of  the  main  glacier  from  which  it  departs.  On  the  disap- 
pearance of  the  ice,  a  hanging  valley  will  be  left  above  the  floor 
of  the  master  valley  ;  but  in  this  case  the  drainage  of  the  hangv 
ing  valley  will  be  away  from,  not  toward,  the  master.  Here  we\ 
probably  have  the  explanation  of  those  broad  hanging  valleys  \ 
which  lead  from  the  valley  of  lake  Maggiore  on  the  west  and,  \ 
less  distinctly,  from  that  of  lake  Como  on  the  east  to  the  com- 
pound basin  of  the  intermediate  lake  Lugano.  On  going  south- 
ward by  rail  from  Bellinzona  to  Lugano,  along  a  stretch  of  the 
St.  Gotthard  route  between  the  great  tunnel  and  Milan,  the  rail- 
way obliquely  ascends  Monte  Ceneri,  the  southeastern  wall  of 
the  trough-like  valley  of  the  Ticino  just  above  the  head  of  lake 
Maggiore  ;  and  at  a  height  of  several  hundred  feet  over  the 
delta  flood  plain  the  line  turns  off  southward  into  the  bleak  dale 
of  the  Leguana,  a  well-marked  hanging  valley  in  which  the  stream 
run^  away  from  the  Ticino  to  lake  Lugano.  The  notch  made  by 
this  supposed  glacial  distributary  is  a  conspicuous  feature  in  the 
view  from  Bellinzona  and  thereabouts. 


GLACIAL  EROSION  667 

The  anomalous  forking  of  lake  Como  and  the  open  branch 
from  the  main  valley  of  the  Rhine  at  Sargans  through  the  trough 
of  Wallen  See  to  lake  Zurich  appear  to  be  the  paths  of  large 
glacial  distributaries  which  eroded  their  channels  deeply  across 
divides  that  presumably  existed  in  pre-glacial  time.  The  west 
wall  of  the  main  valley  of  the  Isere  in  the  Alps  of  Dauphiny, 
southeastern  France,  is  deeply  breached  by  passes  that  lead  north- 
west to  the  troughs  of  lakes  Annecy  and  Bourget,  through  which 
the  distributaries  of  the  Isere  glacial  system  must  have  flowed. 
Lugeon  (62-70)  has  explained  the  breaches  as  marking  the 
former  northwest  paths  of  transverse  members  of  the  Isere  sys- 
tem, from  which  they  have  been  diverted  by  the  subsequent 
growth  of  the  main  longitudinal  valley  —  that  northeast-south- 
west part  known  as  the  Gresivaudan  —  above  Grenoble.  His 
discussion  of  the  problem  takes,  however,  no  account  of  the 
modification  of  valley  depth  by  glacial  erosion  ;  and  as  this  modi- 
fication must  have  been  considerable  (for  the  valleys  hereabouts 
have  superb  basal  cliffs,  as  appears  in  the  valley  of  the  Romanche 
by  Bourg  d'Oisans),  it  may  well  be  that  the  rearrangement 
of  river  courses  in  this  interesting  region  is  not  altogether  the 
work  of  river  action.  Similarly,  the  various  modifications  of 
the  Rhine  drainage  system  in  eastern  Switzerland,  explained 
by  Heim  as  the  work  of  streams  alone,  may  come  to  be,  at  least 
in  part,  referred  to  ice  erosion. 

It  may  be  further  supposed  that  if  the  pre-glacial  valleys  were 
so  arranged  that  a  glacial  distributary  found  a  shorter  and  steeper 
course  to  the  piedmont  plain  or  to  the  sea  than  that  followed  by 
the  master  glacier,  the  distributary  might  under  a  long-enduring 
glaciation  become  the  main  line  of  glacial  discharge  ;  and  if  so, 
it  could  be  eroded  to  a  greater  depth  than  the  former  master 
valley  at  the  point  of  divergence.  In  such  a  case  the  post-glacial 
river  drainage  would  differ  significantly  from  the  pre-glacial. 
There  is  reason  for  believing  that  examples  of  this  kind  are  to 
be  found  in  Norway,  the  evidence  of  which  will  soon  be  pub- 
lished in  an  essay  by  Barrett.  The  diversion  of  the  head  of  a 
stream  in  the  Sierra  Costa  of  northwestern  California  to  a 
deeper-lying  valley  through  a  gorge  cut  by  a  glacial  distributary 
has  lately  been  described  by  Hershey  (47). 


668  PHYSIOGRAPHIC  ESSAYS 

The  Depth  of  Mature  Glacial  Channels.  The  depth  with  respect 
to  sea-level  to  which  the  channels  of  a  glacial  system  may  be 
eroded  when  the  graded  condition  is  reached  is  a  subject  of 
special  interest.  For  many  miles  along  the  lower  course  of  a 
branchless  trunk  glacier  its  volume  is  lessened  by  melting  and 
evaporation,  and  at  its  end  the  ice  volume  is  reduced  to  zero ; 
slow  ice  motion  being  progressively  replaced  by  rapid  water 
motion.  In  such  a  case  the  law  of  continuity  does  not  demand 
that  the  ice  velocity  shall  be  inversely  proportional  to  the  area 
of  the  cross  section,  as  is  the  case  in  the  normal  river  (where  it 
is  assumed  that  there  is  no  loss  by  evaporation).  Indeed,  in  the 
lower  trunk  of  a  mature  glacier  it  may  well  be  that  the  velocity 
of  ice  movement  is  in  a  rough  way  directly  proportional  to  cross- 
section  area.  This  appears  to  be  verified  by  measurements  of 
the  Rhone  glacier,  where  the  mean  annual  movement  is  110 
meters  in  the  heavy  trunk  above  the  cascade,  27  meters  just 
below  the  cascade,  and  only  5  meters  close  to  the  melting  front 
(Forel,  203).  Evidently,  then,  the  erosion  of  the  glacial  bed,  in 
so  far  as  it  is  determined  by  the  pressure  and  motion  of  the  ice 
stream,  will  have  its  maximum  some  distance  upstream  from  the 
end  of  the  glacier  (J.  Geikie,  b,  236).  The  glacial  channel  must 
therefore  become  narrower  and  shallower  as  its  end  is  nearea, 
as  has  already  been  stated.  If  the  glacier  ends  some  distance 
inland  from  the  sea,  its  action  will  be  conditioned  by  the  grade\ 
and  length  of  the  river  that  carries  away  the  water  and  waste  \ 
from  its  lower  end.  The  deepening  of  the  distal  part  of  the  \ 
channel  accomplished  in  youth  might  be  followed  by  a  shal- 
lowing for  a  time  during  maturity,  when  the  accumulation  of 
morainal  and  washed  materials  in  front  of  the  glacier  compelled 
its  end  to  rise.  Now  it  may  well  be  conceived  that  the  surface 
slope  of  such  a  glacier  near  its  end  is  less  than  the  angle  between 
the  surface  and  the  bottom  of  the  glacier ;  and  in  this  case  the 
glacial  floor  must  become  lower  and  lower  for  a  certain  distance 
upstream.  If  such  a  glacier  should  melt  away,  the  distal  part 
of  its  channel  would  be  occupied  by  a  lake,  although  even  the 
head  of  the  lake  may  not  reach  to  the  locus  of  maximum  glacial 
erosion.  Lakes  Maggiore,  Como,  and  Garda  seem  to  occupy 
basins  whose  distal  inclosure  by  heavy  moraines  and  sheets  of 


GLACIAL  EROSION  669 

overwashed  gravels  has  added  to  the  depth  produced  by  erosion 
farther  upstream.  It  would  seem,  however,  that  a  lake  basin 
thus  situated  must  be  only  a  subordinate  incident  in  the  general 
erosion  of  the  whole  length  of  the  glacial  channel.  Too  much 
attention  has,  as  a  rule,  been  given  to  lakes  of  this  kind,  and 
not  enough  to  the  other  effects  of  glacial  action ;  it  seems 
especially  out  of  proportion  to  suppose  that  the  maximum  ero- 
sion by  a  glacier  takes  place  near  its  end,  as  has  been  done 
by  spnie  authors,  on  account  of  the  prevalent  occurrence  of 
Jakes  in  this  situation. 

If  a  glacier  advances  into  the  sea  and  ends  in  an  ice  cliff, 
from  which  ice  blocks  break  off  and  float  away,  something  of  a 
basin-like  form  of  its  lower  channel  may  be  produced ;  but  the 
dimensions  of  this  basin  will  be  determined  by  the  climate  at 
the  termination  of  the  glacier.  If  the  climate  is  such  as  to  allow 
the  glacier  to  enter  the  sea  in  maximum  volume,  then  a  basin  is 
not  to  be  expected.  The  more  the  glacier  diminishes  towards  its 
end,  the  less  erosion  and  the  more  deposition  may  occur  beneath 
it,  and  the  more  of  a  basin  may  be  developed  inland  from  its  end. 

The  depth  to  which  a  glacier  may  cut  its  channel  when  it 
enters  the  sea  is  of  particular  importance.  If  the  glacier  is 
1000  feet  thick  at  its  end,  it  must  continue  to  press  upon  and 
scour  its  bed  until  only  about  140. feet  of  ice  remain  above 
sea-level ;  its  channel  will  thus  be  worn  more  than  800  feet  be- 
neath sea-level.  Truly,  the  latter  part  of  this  work  will  be  per- 
formed with  increasing  slowness  ;  but  if  time  enough  be  allowed, 
the  work  must  be  accomplished,  just  as  is  the  case  with  rivers. 
If  a  glacier  should  melt  away  from  its  deep  intrenchment,  its 
channel  would  be  occupied  by  an  arm  of  the  sea,  or  fiord,  reach- 
ing many  miles  into  the  land.  The  fiord  might  be  shallower  at 
its  mouth  than  farther  inland,  if  differential  erosion  and  deposi- 
tion had  occurred  along  its  channel.  Yet  even  this  result  is 
analogous  to  the  case  of  a  river ;  for  if  the  Mississippi  were  to 
disappear  in  a  prolonged  drought,  a  slender  arm  of  the  sea  would 
invade  the  river  channel  many  miles  upstream  from  the  delta 
front.  Indeed,  the  Mississippi  offers  an  excellent  example  of  a 
channel  that  is  basined  inward  .from  the  river  mouth  ;  for  while 
it  is  only  a  score  of  feet  deep  at  the  passes  where  most  of  its 


6 70  PHYSIOGRAPHIC  ESSAYS 

sediment  is  deposited,  it  is  several  score  of  feet  in  depth  farther 
upstream ;  and  the  slender  arm  of  the  sea  that  would  occupy 
its  channel  if  it  should  disappear  by  climatic  change  would 
be  truly  fiord-like  in  having  a  less  depth  at  its  mouth  than 
farther  inland. 

An  important  corollary  from  this  conclusion  —  perhaps  not  so 
much  of  a  novelty  to  glacial  erosionists  as  to  their  confreres  of 
the  opposite  opinion  —  is  that  the  depth  of  water  in  the  fiords 
of  a  strongly  glaciated  coast  is  not  a  safe  guide  to  the  movement 
of  the  land  since  pre-glacial  time.  If  there  had  been  a  stillstand 
of  the  earth's  crust  through  the  whole  glacial  period,  the  pre- 
glacial  river  channels  that  were  graded  down  a  little  below  sea- 
level  at  their  mouths  would  be  replaced  by  glacial  channels  that 
might  be  eroded  hundreds  of  feet  below  sea-level.  The  depth  of 
fiords  thus  seems  to  depend  on  the  size  of  their  ancient  glaciers, 
on  the  height  of  the  mountain  background,  and  on  the  duration 
of  the  glacial  period,  as  well  as  on  movements  of  the  land.  If 
liberal  measures  of  glacial  erosion  and  glacial  time  are  allowed, 
no  depression  of  glaciated  coasts  since  pre-glacial  time  is  needed 
to  account  for  their  peculiar  features.  The  glacial  channels  may 
have  been  simply  invaded  by  the  sea,  as  the  ice  melted  away, 
without  any  true  submergence.  \ 

Even  the  advocates  of  strong  glacial  erosion  do  not  seem  to 
have  explicitly  recognized  the  full  importance  of  this  possibility. 
James  Geikie,  for  example,  writes  :  "The  fiords  of  high  latitudes 
and  the  narrow  inlets  of  non-glaciated  lands  are  simply  sub- 
merged land-valleys  ;  the  intricate  coast-lines  of  such  regions 
have  been  determined  by  preceding  sub-aerial  denudation." 
Again :  "  In  a  word,  fiords  are  merely  the  drowned  valleys  of 
severely  glaciated  mountain-tracts"  (3,  263,  250).  The  deep 
waters  in  the  valley  of  the  Hudson  through  the  Highlands  of 
southeastern  New  York  are  the  most  fiord-like  in  the  eastern 
United  States,  and  they  are  universally  explained  as  the  result 
of  submergence  of  a  normal  river  valley ;  but  the  constricted 
ice  current  that  must  have  flowed  through  the  Highland  gorge 
may  have  been  energetic  enough  to  deepen  its  bed  beneath  sea- 
level,  and  since  the  ice  melted  away,  who  can  say  how  much  sub- 
mergence beneath  pre-glacial  levels  has  taken  place !  I  do  not 


GLACIAL  EROSION 


67I 


know  how  far  this  view  of  the  matter  has  been  taken  by  earlier 
advocates  of  strong  glacial  erosion,  but,  for  my  own  part,  the 
acceptance  of  such  a  possibility  means  a  complete  reversal  of 
the  belief  that  I  held  two  years  ago.  The  reversal  is,  however, 
accompanied  by  the  memory  that  it  was  always  difficult  to 
understand  why  submergence  and  glaciation  were  so  closely 
associated ;  even  if  glaciation  had  caused  depression,  it  was 
difficult  to  understand  why  the  relief  from  ice  pressure  in  post- 
glacial time  had  not  now  been  followed  by  a  rise  of  the  land 
much  nearer  to  its  former  altitude  than  would  be  the  case  if  the 
greater  part  of  the  depth  of  fiords  is  explained  by  submergence. 


FIG.  106.   DIAGRAM  SECTION  OF  A  LATERAL  VALLEY  WITH  A 
CORRIE  BASIN 

The  Origin  of  Corrie  Basins.  On  pursuing  the  above  line  of 
consideration  a  little  further,  it  may  give  some  light  on  the  occur- 
rence of  the  small  rock  basins  that  are  so  often  found  in  the  floor 
of  cliff-walled  corries.  Imagine  that  a  large  glacial  system  has 
become  maturely  established,  and  that  it  "rises"  in  many  blunt 
head-branches  that  have  excavated  corries  in  a  pre-glacial  moun- 
tain mass,  and  have  cut  down  channels,  at  their  junction  with 
the  larger  branches  or  trunk  glacier,  to  a  depth  appropriate  to 
their  volume.  Unless  the  erosion  of  the  corries  has  been  guided 
by  differences  of  rock  structure,  there  does  not  seem  to  be  reason 
for  their  possessing  a  basined  floor  at  this  stage  of  development ; 
but  if  a  change  of  climate  should  now  cause  the  trunk  glacier  to 


672  PHYSIOGRAPHIC  ESSAYS 

disappear,  while  many  of  the  blunt  head-branches  remain  in 
their  corries,  each  little  glacier  thus  isolated  will  repeat  the  con- 
ditions of  erosion  above  inferred  for  the  trunk  glacier ;  and  if 
this  style  of  glaciation  linger  long  enough,  rock  basins  may  very 
generally  characterize  the  floors  of  the  corries  when  the  ice  finally 
melts  away.  Fig.  106  may  make  this  clearer.  Let  the  broken  line 
ABC  be  the  slope  of  a  pre-glacial  lateral  ravine  which  reaches 
a  trunk  stream  at  C,  while  ADC  is  the  profile  of  an  adjoining 
lateral  spur.  After  vigorous  and  mature  glaciation  the  dotted 
line  GE  may  represent  the  surface  slope  of  a  lateral  glacier, 
and  GHJ  that  of  the  lateral  glacier  bed  ;  while  EFL  is  the  sur- 
face of  the  trunk  glacier,  and  EKL  the  bed.  The  lower  part  of 
the  lateral  spur  has  been  cut  off  to  make  the  basal  cliff  beneath 
D.  On  the  disappearance  of  the  trunk  glacier  at  this  stage,  the 
shrunken  side  glacier  GNJH  occupies  its  corrie,  or  hanging 
valley,  which  opens-  at  J  on  the  over-steepened  wall  DJK  of  the 
evacuated  channel  of  the  trunk  glacier.  Let  the  maximum 
erosion  of  the  corrie  glacier,  as  conditioned  by  pressure  and 
motion,  be  at  H.  Then  after  some  time  the  weathering  of  the 


t 

tin 


cliff  walls  and  the  erosion  of  the  floor  will  have  transformed  the 
corrie  and  its  glacier  to  a  form  G* N1  f  H\  such  that  the  deep- 
ening of  the  glacial  bed  should  be  a  maximum  at  HH* .  The 
continuous  slope  of  the  glacial  bed  GHJ,  appropriate  to  the 
time  when  the  lateral  glacier  joined  the  trunk  glacier,  may  thus 
be  transformed  into  a  basined  curve,  G1  Hf  j',  appropriate  to  a 
small  glacier  terminating  at/';  and  on  the  disappearance  of  the 
small  glacier,  a  tarn  or  rock-basin  lake  may  occupy  the  depres- 
sion at  H1 .  It  is  on  the  basis  of  a  supposition  like  this  that  a 
determination  has  been  attempted  of  the  altitude  at  which  the 
shrinking  remnants  of  an  extensive  glacial  system  endured  for 
a  time  before  their  entire  disappearance  (J.  Geikie,  b,  233). 
Richter's  supposition  that  the  uplands  of  Norway  result  from 
the  consumption  of  preexistent  mountains  by  the  great  exten- 
sion of  corrie-glacier  floors,  each  similar  to  J' H\  thus  seems 
mechanically  possible ;  but  it  is  nevertheless  climatically  very 
improbable,  and  it  seems  to  me  deficient  in  not  attributing  a 
greater  amount  of  work  to  normal  stream  erosion  in  pre- 
glacial  time. 


GLACIAL  EROSION  673 

Over-deepened  Valleys  and  Over-steepened  Walls.  As  in  the 
case  of  the  normal  cycle  of  denudation  in  which  the  life  history 
of  river  systems  is  involved,  so  in  the  glacial  cycle,  all  manner 
of  complications  may  arise,  causing  great  departures  from  the 
ideal  case.  The  assumed  initial  land  form  may  be  a  surface 
previously  more  or  less  dissected  by  river  erosion,  on  which 
glaciers  must  then  proceed  to  develop  a  drainage  system  appro- 
priate to  their  own  peculiar  needs,  as  has  been  partly  consid- 
ered above  in  connection  with  glacial  distributaries.  It  will  be 
instructive  to  make  out  a  good  series  of  examples  illustrating 
different  combinations  of  river  and  glacial  action,  and  including 
young,  mature,  and  old  river  valleys,  modified  by  young  or  ma- 
ture glaciation.  For  example,  the  existing  valley  of  the  Rhue 
in  the  Central  Plateau  of  France  shows  a  sub-mature  river  valley 
with  incised  meanders,  moderately  affected  by  young  and  rela- 
tively light  glaciation ;  the  valley  of  the  Ticino  in  the  southern 
Alps  is  a  well-matured  pre-glacial  river-valley  system,  modified 
by  strong  sub-mature  glaciation.  The  fiords  of  Norway  result 
from  the  sub-mature  and  intense  glaciation  of  a  river-valley 
system  whose  stage  of  pre-glacial  development  is  not  yet  well 
determined. 

Interruptions  of  regular  progress  in  the  glacial  cycle  must, 
as  in  the  river  cycle,  be  occasioned  by  elevation,  depression,  or 
deformation  of  the  land  mass  ;  but  no  examples  of  complications 
of  this  kind  can  be  adduced.  Variations  of  climate  may  replace 
creeping  glaciers  in  young,  mature,  or  old  stages  of  development 
by  flowing  rivers ;  and  the  early  stages  of  such  rivers  are 
of  much  importance  among  existing  geographical  forms.  Lakes, 
delaying  the  river  flow,  occupy  the  depressions  of  the  glaciated 
surface,  as  has  been  known  since  Ramsay  first  pointed  out  the 
correlation  of  lacustrine  and  glaciated  regions  in  1861  ;  but  the 
analogy  between  lakes  in  the  beds  of  melted  glaciers  and  pools 
in  the  beds  of  dried-up  rivers  has  perhaps  not  been  sufficiently 
insisted  upon.  Waterfalls  connect  the  streams  that  occupy  the 
discordant  beds  of  glacial  channels,  as  has  lately  been  clearly  set 
forth.  Landslides  frequently  occur  after  the  supporting  glacier 
withdraws  from  the  over-steepened  banks  of  its  huge  channel ; 
fallen  masses  of  this  origin  have  been  repeatedly  mistaken  for 


674  PHYSIOGRAPHIC  ESSAYS 

moraines  in  Alpine  valleys,  as  has  been  lately  shown  by  Bruck- 
ner. Every  lake  or  fiord  is  an  effective  lowering  of  base-level 
for  the  stream  above  it ;  for  the  level  of  a  body  of  standing 
water  is  essentially  the  same  at  both  ends.  As  fast  as  the 
inflowing  river  builds  its  delta  forward  at  the  head  of  the  lake 
or  fiord,  its  flood  plain  must  rise  upstream  and  aggrade  the  val- 
ley floor.  This  process  is  very  pronounced  in  many  Alpine 
valleys,  where  the  aggraded  valley  floor  has  a  relatively  rapid 
descent  on  account  of  the  plentiful  and  coarse  detritus  furnished 
by  the  active  side  streams.  Indeed,  every  ravine  furnishes  a 
great  quantity  of  rock  waste,  whose  descent  is  analogous  to  re- 
peated landslides  of  small  dimensions.  The  valley  floor  beneath 
the  ravines  is  invaded  by  great  alluvial  fans,  and  the  main  stream 
is  driven  away  toward  the  farther  valley  wall  by  their  rapid  ad- 
vance. At  every  flood  the  waste  supplied  from  the  fans  is  swept 
abundantly  into  the  main  stream,  whose  flood  plain  grows  rapidly 
as  a  delta  in  the  upper  end  of  each  lake  that  it  enters.  The  delta 
of  the  Ticino  seems  to  have  advanced  so  far  into  what  was  origi- 
nally the  basin  of  lake  Maggiore  that  the  apparent  height  of 
the  hanging  lateral  valleys  steadily  decreases  toward  the  laki ; 
and  for  several  miles  above  the  head  of  the  lake  the  lateral 
valleys  seem  to  enter  the  main  valley  almost  at  grade,  although 
there  can  be  little  doubt  that  if  all  the  delta  alluvium  were  re- 
moved, the  lateral  valleys  would  be  found  to  stand  high  above 
the  rock  floor  of  the  main  valley.  The  standing  lakes,  the  ag- 
grading flood  plains,  and  the  growing  fans  all  show  that  the  bed 
of  the  glacial  channel  has  been  worn  too  deep  to  serve  as  a  valley 
floor  for  the  existing  river ;  the  river  must  aggrade,  with  water 
or  with  waste,  the  bed  of  the  channel  that  the  glacier  degraded  ; 
hence  Penck  has  suggested  that  glaciated  valleys  of  the  Alpine 
kind  should  be  called  "  over-deepened."  In  the  same  way,  the 
waterfalls  from  the  hanging  valleys,  the  showering  waste  that 
forms  the  fans,  and  the  landslides  from  the  basal  cliffs,  all  show 
that  the  banks  of  the  glacial  channel  —  the  lower  walls  of  the 
existing  valleys  —  are  too  steep ;  and  they  may  be  therefore 
called  "  over-steepened."  Much  glacial  work  had  to  be  done 
upon  the  mature  pre-glacial  valleys  of  river  erosion  to  bring 
them  into  mature  adjustment  with  the  needs  of  glaciers  ;  much 


GLACIAL  EROSION  675 

river  work  must  likewise  now  be  done  upon  the  over-deepened 
glaciated  valleys,  and  upon  their  over-steepened  walls  and  their 
hanging  branches,  before  they  can  be  maturely  adjusted  again 
to  the  needs  of  rivers. 

Practical  Utility  of  the  Ideal  Glacial  Cycle.  In  every  case  the 
full  understanding  of  the  conditions  developed  by  any  system  of 
glaciers,  existing  or  extinct,  can  be  reached  only  by  a  complete 
analysis  of  the  conditions  under  which  they  began  to  work,  of 
the  energy  with  which  they  worked,  of  the  part  of  a  cycle  during 
which  they  worked,  and  of  the  complications  of  climatic  change 
or  of  crustal  movements  by  which  their  work  was  modified  in 
this  way  or  in  that.  A  partial  analysis  may  suffice  for  a  particular 
instance  ;  but  the  explorer  will  be  better  equipped  for  the  expla- 
nation of  all  the  instances  that  he  discovers  if  he  sets  out  with 
a  well-elaborated  conception  of  the  ideal  glacial  cycle  of  denu- 
dation, and  of  the  complications  it  is  likely  to  suffer.  However 
extensive  and  definite  this  conception  may  be,  exploration  will 
probably  require  its  further  extension  and  definition ;  however 
brief  exploration  may  be,  it  will  probably  be  aided  by  an  orderly 
examination  of  all  pertinent  knowledge  previously  accumulated. 

As  a  practical  instance  of  the  value  of  the  glacial  cycle,  we 
may  consider  the  aid  given  toward  the  solution  of  certain  prob- 
lems by  the  careful  reconstruction  —  or  at  least  the  conscious 
attempt  at  reconstruction  —  of  the  form  of  the  land  surface  on 
which  the  Pleistocene  glaciers  began  their  work,  and  by  the 
legitimate  deduction  of  the  characteristics  of  maturity  in  the 
cycle  of  glacial  erosion.  Beyond  the  mature  stage  we  may 
seldom  have  occasion  to  go,  as  there  do  not  seem  to  be  actual 
examples  of  more  advanced  glacial  work.  The  initial  form  on 
which  Pleistocene  glacial  action  began  is  in  no  case  known  to  be 
that  implied  in  the  opening  paragraphs  of  the  section  on  the 
Glacial  Cycle  ;  namely,  a  land  mass  freshly  uplifted  from  beneath 
the  sea  and  not  previously  carved  by  the  streams  of  an  ordinary 
or  normal  cycle  of  erosion.  In  central  France,  for  example,  the 
initial  form  was  an  uplifted  and  sub-maturely  dissected  peneplain, 
in  which  valleys  with  incised  meanders  had  been  habitually  devel- 
oped. It  was  there  of  the  greatest  assistance  to  carry  into  the 
glaciated  area  a  clear  picture  of  its  pre-glacial  form,  as  determined 


676  PHYSIOGRAPHIC  ESSAYS 

by  generalizing  the  adjacent  non-glaciated  area.  At  the  same 
time,  the  ideal  picture  of  a  maturely  developed  glacial  drain- 
age system,  with  smooth-sided  troughs,  was  seen  to  represent  a 
much  more  advanced  condition  than  was  attained  in  the  rugged 
valley  of  the  Rhue  ;  and  thus  a  tolerably  definite  idea  was  gained 
of  the  youthful  stage  of  glacial  development,  somewhere  between 
its  beginning  and  its  maturity,  and  of  the  amount  of  destructive 
work  needed  to  reach  this  youthful  stage.  This  elementary 
example  illustrates  a  method  embodying  the  cycle  of  glacial 
denudation  that  ought  to  be  applied  whenever  possible. 

The  larger  Norwegian  fiords  may  be  instanced  as  glacial 
channels  that  present  every  appearance  of  having  advanced  far 
toward  the  mature  stage  of  a  cycle  of  glacial  denudation  from 
an  initial  or  pre -glacial  form  not  yet  well  understood.  The  vari- 
ation of  form  between  the  main  fiords  and  their  branches  gives 
some  indication  that  the  glacial  work  was  accomplished  in  several 
successive  epochs,  with  the  interglacial  epochs  of  normal  riv 


V   ^ 


:r 

work  between  ;  but  this  is  only  a  suggestion,  needing  much  moVe 
field  work  before  it  can  be  assured.  Not  only  the  deep  fiords, 
but  the  hanging  valleys  and  the  uplands,  also,  have  been  ice- 
scoured  ;  for  hanging  valleys  frequently  have  a  well-defined 
U-section,  and  sometimes  receive  secondary  hanging  valleys 
from  the  inclosing  uplands ;  and  the  streams  of  the  uplands 
exhibit  repeated  departures  from  the  forms  of  normal  erosion. 
Although  possessing  little  drift,  the  uplands  frequently  bear 
lakes  of  moderate  depth  and  irregular  outline  ;  in  spite  of  the 
breadth  to  which  the  upland  valleys  are  opened  between  the  sur- 
mounting hills  and  mountains,  their  streams  frequently  change 
from  wandering  at  leisure  in  split  or  braided  channels  along 
broad  floors,  to  dashing  down  in  haste  over  rocky  rapids  :  a 
behavior  that  is  manifestly  inconsistent  with  that  of  the  mature 
drainage  of  a  normally  denuded  region.  Even  the  surmounting 
hills  exhibit  strong  scouring  on  their  up-ice-stream  side.  It  does 
not  therefore  seem,  permissible  to  conclude  that  the  hanging 
valleys  which  open  on  the  walls  of  the  greater  fiords  have  not 
been  deepened  by  ice  erosion  because  they  escaped  the  more 
severe  glaciation  that  scoured  out  the  fiords  themselves.  All 
the  valleys  have  been  glaciated,  and  all  have  been  significantly 


GLACIAL  EROSION  677 

modified  from  their  pre-glacial  form.  The  discordance  of  over- 
deepened  main  fiord  and  hanging  lateral  valley  seems  to  me 
best  explained  as  the  result  of  the  mature  development  of  gla- 
cial drainage,  in  which  the  chief  trunks  and  the  larger  branches 
of  the  glacial  systems  had  for  the  most  part  reached  a  graded 
condition.  Trunk  and  branch  glaciers  would  then  have  united 
at  even  grade  as  to  their  upper  surface,  and  the  trunk  and 
branch  channels  would  have  had  dimensions  satisfactory  to  the 
ice  currents  which  flowed  through  them,  but  the  channel  beds 
would  have  been  discordant,  as  they  are  found  to  be. 

REVIEW  OF  PREVIOUS  WRITINGS  ON  HANGING  VALLEYS 

It  has  already  been  stated  that  hanging  side  valleys  and  over- 
deepened  main  valleys  have  not  yet  been  generally  given  the 
importance  that  they  deserve  as  witnesses  to  strong  glacial 
erosion.  Russell,  in  his  ''Glaciers  of  North  America"  (1897), 
makes  no  mention  of  discordant  lateral  and  main  valleys  when 
discussing  glacial  erosion.  James  Geikie,  in  his  "  Earth  Sculp- 
ture "  (1898),  allows  to  discordance  of  glaciated  valleys  hardly 
more  than  a  secondary  importance  in  abstracts  and  quotations 
from  Wallace's  accounts  of  Alpine  lakes  and  from  Richter's 
essay  on  Norway  (see  below),  while  the  glacial  erosion  of  lake 
basins  is  much  more  fully  treated.  Yet  of  all  the  facts  that 
point  to  strong  glacial  erosion,  none  seem  to  give  testimony  so 
unanswerable  as  do  hanging  valleys.  The  following  extracts 
will  serve  to  illustrate  the  gradually  increasing  recognition  of 
their  importance. 

Forbes  on  the  Waterfalls  of  Norway.  Thinking  that  some 
interesting  early  observations  on  the  hanging  valleys  of  Norway 
might  be  recorded  in  Forbes'  book  of  travels  in  that  country,  I 
looked  up  waterfalls  in  his  index  and  there  found  a  reference  to 
the  cause  of  their  profusion,  which  was  stated  as  follows  : 

The  source  of  this  astonishing  profusion  of  waters  is  to  be  found  in  the 
peculiar  disposition  of  the  surface  of  the  country  so  often  referred  to.  The 
mountains  are  wide  and  flat,  the  valleys  are  deep  and  far  apart.  ...  As  the 
valleys  ramify  little  .  .  .  and  are  wholly  disconnected  from  \hzfjelds  [up- 
lands] by  precipitous  slopes,  it  follows  that  the  single  rivers  which  water 


678  PHYSIOGRAPHIC  ESSAYS 

those  valleys  .  .  .  are  supplied  principally  by  streamlets  which,  having  run 
long  courses  over  i\\zfjelds,  are  at  last  precipitated  into  the  ravines  in  the 
form  of  cascades  (251). 

Forbes  was  an  excellent  observer,  yet  this  quotation  is  about 
equivalent  to  saying  that  there  are  many  waterfalls  in  Norway 
because  there  are  steep  slopes  over  which  the  streams  of  the 
uplands  must  descend.  The  quotation  deserves  a  place  here  if 
for  nothing  more  than  to  show  the  advance  of  a  half  century  in 
regard  to  what  constitutes  the  cause  of  a  geographical  feature. 

McGee  on  Glacial  Canons,  1883.  The  earliest  article  that  I 
have  found  touching  on  this  subject  is  the  brief  abstract  of  a 
paper  read  by  McGee  before  the  American  Association  in  1883, 
entitled  "  Glacial  Canons."  Observations  in  the  Sierra  Nevada 
led  this  keen  observer  to  state  that  \ 

the  effect  of  the  temporary  occupancy  of  a  typical  water-cut  cano  i  by 
glacier  ice  will  be  to  (i)  increase  its  width,  (2)  change  the  original  V 
to  a  U  cross  profile,  (3)  cut  off  the  terminal  portions  of  tributary  canons 
and  thus  relatively  elevate  their  embouchures,  (4)  intensify  certain  irregu- 
larities of  gradient  in  the  canon  bottom,  (5)  excavate  rock  basins,  (6)  develop 
cirques,  and,  in  general,  transform  such  canon  into  an  equally  typical  glacial 
canon  (a,  238). 

A  later  paper  by  the  same  author  is  referred  to  below. 

Hanging  Valleys  in  the  Alps.  Valleys  that  are  here  called 
"  hanging  "  have  frequently  been  described  by  observers  in  the 
Alps,  but  either  without  particular  reference  to  their  discordant 
relation  to  the  main  valleys,  or  with  acceptance  of  normal  ero- 
sion in  the  main  valley  as  the  cause  of  their  discordance.  Riiti- 
meyer's  and  Heim's  views  on  discordant  lateral  valleys  have 
been  already  referred  to. 

An  account  of  the  Salzachthal  in  the  Tyrol,  by  Bruckner, 
describes  it  as  one  valley  in  the  bottom  of  another ;  the  deeper 
one  being  relatively  narrow  and  steep-sided,  while  the  sides  of 
the  higher  valley  flare  wide  open  ;  the  side  streams  are  described 
as  falling  into  the  deeper  main  valley ;  but  this  significant  fea- 
ture is  not  mentioned  as  if  it  were  of  general  occurrence,  nor 
is  it  explained  by  glacial  erosion  (95). 

Lubbock,  in  his  "  Scenery  of  Switzerland,"  follows  Riitimeyer 
and  Heim.  After  stating  that  the  side  valleys  of  the  Reuss 


GLACIAL  EROSION  679 

have  a  moderate  grade  which  brings  them  out  at  the  level  of 
one  of  the  terraces,  or  Thalstufen,  of  the  main  valley,  from  which 
their  streams  cascade  down  into  the  main  stream,  Lubbock  writes  ; 

It  is  obvious  that  this  terrace  represents  a  former  7^halwegoi  the  Reuss 
with  much  less  fall  than  it  has  now,  and  that  the  river  has  deepened  its 
valley  more  rapidly  than  the  lateral  streams,  so  that  these  glens  open  at 
some  distance  up  the  side  of  the  valley,  and  their  waters  join  the  Reuss  by 
rapids  or  waterfalls.  .  .  .  The  valley  shows  clear  evidence  of  glacial  action. 
The  hard  rocks  are  in  places  quite  polished.  This  is  especially  the  case 
with  the  buttresses  which  stand  like  doorposts  where  the  lateral  glens  open 
into  the  main  valley,  and  particularly  on  the  right  side  of  the  eastern  glens, 
the  left  of  the  western,  where  of  course  the  pressure  of  the  ice  was  greatest 
(332,  334). 

Russell  on  Hanging  Valleys,  1887.  Russell  gave  a  detailed 
account  of  what  may  be  called  hanging  valleys  in  his  report  on 
the  "Quaternary  History  of  Mono  Valley,  California."  In  a  section 
on  "  high  lateral  canons,"  he  says  : 

In  a  number  of  instances  in  the  Mono  basin  the  low-grade  glaciated 
canons  receive  branching  canons  at  a  considerable  elevation  above  their 
bottoms,  the  branches  also  having  a  low  grade.  This  is'  illustrated  where 
lake  Canon  opens  into  Lundy  Canon.  Each  of  these  gorges  has  an  ap- 
proximately horizontal  bottom  near  the  place  of  union,  but  the  former  is  a 
thousand  feet  higher  than  the  latter.  The  stream  flowing  through  lake 
Canon  descends  precipitously  over  a  rocky  face  in  order  to  join  Lundy 
Creek.  The  bottom  of  the  higher  canon  is  about  on  a  level  with  the  main 
lateral  moraine  in  the  lower  canon.  The  same  series  of  phenomena  is 
repeated  where  Silver  Creek  descends  over  a  rocky  face  to  join  Rush 
Creek.  ...  It  might  be  assumed  that  the  main  canons  had  been  excavated 
by  glacial  action  more  deeply  than  the  lateral  branches,  owing  to  the 
greater  eroding  power  of  the  glaciers  which  occupied  them.  This  is  a 
simple  and  natural  explanation  of  the  conditions  observed,  and  if  we  admit 
the  great  amount  of  erosion  usually  assumed  for  ancient  glaciers,  it  must 
be  accepted  as  an  adequate  cause  for  the  great  strength  of  the  main  chan- 
nels of  ice  discharge.  To  the  writer  ...  it  appears  that  the  main  work  of 
sculpture  in  the  Sierra  Nevada  ...  is  to  be  attributed  to  water  erosion, 
v/hile  only  minor  features  .  .  .  are  to  be  referred  to  glacial  action.  With 
this  conclusion  in  mind,  the  great  inequality  in  the  depth  of  the  main  gla- 
cial troughs  and  of  their  lateral  branches  is  too  great  a  work  to  be  ascribed 
to  the  erosive  power  of  ice  (351-352). 

The  hanging  valleys  are  therefore  left  without  explicit  ex- 
planation, but  it  appears  from  other  pages  of  the  report  that 


680  PHYSIOGRAPHIC  ESSAYS 

several  of  the  deeper  canons,  such  as  Lundy,  now  head  to  the 
west  of  the  general  line  of  mountain  crest,  and  it  is  therefore 
possible  that  they  are  examples  of  retrogressive  erosion,  both  by 
water  and  by  ice,  since  the  elevation  of  the  Sierra  Nevada.  If 
this  be  the  case,  the  hanging  valleys  may  be  remnants  of  an 
ancient  west-flowing  drainage  system,  now  diverted  to  a  more 
rapid  eastward  descent.  Some  such  meaning  may  be  behind 
Russell's  words  :  "  Many  of  the  valleys  of  the  Sierra  Nevada . . . 
are  in  fact  relics  of  a  drainage  system  which  antedates  the  exist- 
ence of  the  Sierra  as  a  prominent  mountain  range"  (348!,  350). 

Wallace  on  Glaciated  Valleys,  i8pj.  One  of  the  most  I  appre- 
ciative statements  that  I  have  found  concerning  hanging  valleys 
is  an  article  by  Wallace  on  "The  Ice  Age  and  its  Work,"  which 
presents  many  arguments '  in  favor  of  the  strong  erosive  power 
of  glaciers.  Wallace  says  : 

It  is  evident  that  ice  erosion  to  some  extent  must  have  taken  place  along 
the  whole  length  of  the  glacier's  course,  and  that  in  many  cases  the  result 
might  be  simply  to  deepen  the  valley  all  along,  not  quite  equally,  perhaps, 
but  with  no  such  extreme  differences  as  to  produce  a  lake  basin. 

Then  after  giving  much  emphasis  to  the  excavation  of  lake 
basins  near  the  lower  end  of  a  large  glacier,  where  the  erosive 
power  is  deductively  argued  to  be  at  its  maximum,  Wallace 
examines  several  lakes  to  discover  if  those  of  glacial  origin 
have  not  some  distinctive  feature  by  which  they  can  be  recog- 
nized. He  points  out  that  greater  length  than  breadth,  and 
simplicity  of  outline,  are  highly  significant  of  glacial  erosion, 
and  that  the  absence  of  lateral  bays  and  branches  is  strongly 
against  the  theory  of  warping  or  submergence.  In  this  connec- 
tion it  is  recognized  that 

the  lake  surface,  not  the  lake  bottom,  represents  approximately  the  level  of 
the  pre-glacial  valley,  and  that  the  lateral  streams  and  torrents  enter  the 
lake  in  the  way  they  do  because  they  could  only  erode  their  channels  down 
to  the  level  of  the  old  valley  before  the  ice  overwhelmed  it.  ...  In  connec- 
tion with  this  subject  may  be  noticed  the  many  cases  in  which  Alpine 
valleys  present  indications  of  having  been  greatly  deepened  by  glacial 
erosion,  although,  owing  either  to  the  slope  of  the  ground  or  to  the  uni- 
formity of  the  ice-action,  no  lake  has  been  produced.  In  some  valleys, 
as  in  that  of  Lauterbrunnen,  the  trough  between  the  vertical  rock-walls  was 
probably  partly  formed  before  the  ice  age,  but  was  greatly  deepened  by 


GLACIAL  EROSION  68 1 

glacial  erosion,  the  result  being  that  the  tributary  streams  have  not  since 
had  time  to  excavate  ravines  of  equal  depth  with  the  main  valley,  and  there- 
fore form  a  series  of  cascades  over  the  lateral  precipices,  of  which  the 
Staubbach  is  the  finest  example.  In  many  other  cases,  however,  the  side 
streams  have  cut  wonderfully  narrow  gorges  by  which  they  enter  the  main 
valley  (a,  754,  768). 

Me  Gee  s  Second  Paper  on  Glacial  Canons,  1894.  McGee  has 
given  a  fuller  statement  of  the  action  of  glacial  erosion  in  pro- 
ducing discordance  between  lateral  and  main  valleys  in  a  second 
essay,  again  entitled  "  Glacial  Canons,"  published  eleven  years 
after  his  first  essay  on  this  subject.  After  a  discussion  of  glacial 
erosion  in  general,  it  is  stated  that 

glacial  canons  are  characterized  by  several  peculiar  features:  (i)  they  are 
U-shaped  rather  than  V-shaped  in  cross-profile  ;  (2)  small  tributary  gorges 
usually  enter  at  levels  considerably  above  the  canon-bottoms  ;  (3)  in  longi- 
tudinal profile  the  canon-bottoms  are  irregularly  terraced,  —  i.e.  made  up  of 
a  series  of  rude  steps  of  variable  form  and  dimensions,  —  and  some  of  the 
terraces  are  so  deeply  excavated  as  to  form  rock-basins  occupied  by  lake- 
lets. ...  In  a  region  of  rapid  corrasion  then,  the  main  [water]  stream 
must  .  .  .  more  rapidly  corrade  its  channel  than  does  its  minor  tributary; 
and  the  tributary  canon  must  accordingly  enter  its  principal  over  a  rapid 
or  at  least  a  convex  curve  in  longitudinal  profile.  If  now  the  main  canon 
become  filled  with  ice  and  be  transformed  from  the  V  to  the  U  type  by  its 
action,  the  distal  extremity  of  the  tributary  will  be  cut  off  and  the  original 
stream-formed  declivity  replaced  by  the  precipitous  side-wall  of  the  normal 
glacier  valley  (£,  351,  359). 

It  is  explicitly  stated  by  McGee  that  this  explanation  does 
not  demand  great  glacial  erosion,  because  the  U -canon  of  glacial 
origin  need  not  be  much  deeper,  although  significantly  wider,  than 
the  pre-glacial  V-canon  of  river  origin.  But  the  last  of  the  above 
quotations  postulates  a  special  condition,  —  a  region  of  rapid  pre- 
glacial  corrasion  by  streams,  and  in  so  far  does  not  seem  applica- 
ble to  the  case  of  the  Ticino  or  of  the  many  other  Alpine  valleys  ; 
for  the  well-opened  slopes  of  the  lateral  valleys  and  the  still  wider 
flare  on 'the  upper  slopes  of  the  main  valleys  in  the  Alps  prove 
that  during  their  formation  the  main  stream  must  have  attained 
a  graded  slope  which  the  lateral  streams  must  have  joined  in 
accordant  fashion ;  and  there  is  nothing  to  show  that  the  open 
and  graded  floor  of  the  main  valley  was  significantly  trenched 


682  PHYSIOGRAPHIC  ESSAYS 

by  river  action  in  pre-glacial  time.  On  the  contrary,  the  shallow- 
ness  of  the  trenches  now  found  in  the  lateral  hanging  valleys 
proves  that  even  if  the  main  valley  had  been  trenched,  it  could 
not  have  been  cut  down  very  deep. 

Tarr  on  Cayuga  Lake,  1894.  A  significant  instance  of  dis- 
cordance has  been  pointed  out  by  Tarr  and  taken  by  him  as 
direct  evidence  of  the  glacial  erosion  of  a  lake  basin.  He  shows 
that  the  north  and  south  trough  of  Cayuga  lake,  New  York, 
lying  in  the  line  of  ice  motion,  is  about  three  hundred  feet 
deeper  than  the  floor  of  Salmon  Creek,  a  tributary  whdse  course 
is  oblique  to  the  ice  motion  ;  and  he  ascribes  the  breakW  grade 
between  the  two  valleys  to  greater  erosion  in  the  deeper  one. 
He  generalizes  so  far  as  to  refer  to  lake  Ontario  as  probably 
exhibiting  further  instances  of  discordant  valleys. 

De  Lapparent  on  Hanging  Valleys,  1896.    A  clear  z 


nd  brief 


state'ment  is  made  by  De  Lapparent  in  his  "  Legons  de  Geogra- 
phic Physique,"  as  if  the  matter  were  well  known  and  undisputed. 
Under  the  heading  "  Caracteres  des  vallees  glaciaires,"  he  writes 
in  effect  as  follows : 

When  a  glacier  disappears,  the  lateral  valleys,  which  had  been  eroded 
before  the  glacial  period  with  relation  to  the  local  base-level  determined  by 
the  river  that  the  glacier  afterwards  replaced,  may,  on  the  disappearance  of 
the  ice,  no  longer  present  accordant  junctions  with  the  main  valley.  Cas- 
cades and  rapids  will  therefore  occur  at  their  mouths  in  greater  number 
than  in  a  district  of  the  same  strength  of  relief  which  has  not  been  glaciated. 
All  these  features  are  clearly  seen  in  Norway  (a,  210;  b,  219). 

Richter  on  Norway,  1896.  The  essay  by  Richter,  already  re- 
ferred to,  contains  a  large  number  of  -excellent  observations. 
Regarding  our  special  subject,  he  states  that  many  side  valleys 
in  Norway  open  high  on  the  fiord  walls,  as  if  cut  off  in  the 
deeper  erosion  of  the  main  valleys ;  a  similar  relation  being 
known  in  the  Alps,  but  of  less  distinctness.  The  discordance 
of  valley  depth  in  Norway  is  thought  to  depend  on  the  faster 
erosion  of  the  main  valleys  by  water  or  ice  or  both,  when  the 
side  valleys  and  the  uplands  were  occupied  by  slow-moving  neve*. 
The  side  streams  descending  from  the  floors  of  their  hanging 
valleys  have  not  yet  cut  even  narrow  clefts  in  the  rock  walls 
of  the  main  valleys  (177-1/9). 


GLACIAL  EROSION  683 

J.  Geikie  on  Glacial  Erosion,  1898.  The  recent  volume  on 
" Earth  Sculpture"  by  James  Geikie  gives  a  generally  available 
access  to  the  results  of  Richter's  observations  on  Norway.  The 
following  quotation  comes  after  a  description  of  the  rock  walls 
of  the  fiords: 

Numerous  tributary  waters,  some  of  which  are  hardly  less  important 
than  the  head-stream,  do  indeed  pour  into  the  fiord,  but  they  have  not  yet 
eroded  for  themselves  deep  trenches.  After  winding  through  the  plateau- 
land  in  broad  and  shallow  valleys  their  relatively  gentle  course  is  suddenly 
interruptedj  and  they  at  once  cascade  down  the  precipitous  rock-walls  to 
the  sea.  The  side-valleys  that  open  upon  a  fiord  are  thus  truncated  by  the 
steep  mountain-wall  as  abruptly,  Dr.  Richter  remarks,  as  if  they  had  been 
cut  across  with  a  knife.  .  .  . 

If  we  admit  that  a  fiord  is  simply  a  partially  drowned  land-valley,  and 
that  the  profound  hollow  in  which  it  lies  has  been  eroded  by  river  action, 
how  is  it  that  the  side  streams  have  succeeded  in  doing  so  little  work? 
Why  should  the  erosion  of  the  main  or  fiord-valleys  be  so  immeasurably  in 
advance  of  that  of  the  lateral  valleys  ?  Obviously  there  must  have  been  a 
time  when  the  process  of  valley-formation  proceeded  more  rapidly  along  the 
lines  of  the  present  fiords  and  their  head-valleys  than  in  the  side-valleys 
which  open  upon  these  from  the  fjelds.  At  that  time  the  work  of  rain  and 
running  water  could  not  have  been  carried  on  equally  over  the  whole  land, 
otherwise  we  should  find  now  a  completely  .developed  hydrographic  system 
—  not  a  plateau  intersected  by  profound  chasms,  but  an  undulating  moun- 
tain-land with  its  regular  valleys.  .  .  .  According  to  Dr.  Richter,  the  re- 
markable contrast  between  the  deep  valleys  of  the  fiords  and  the  shallow 
side-valleys  that  open  upon  them  from  the  fjelds  —  the  profound  erosion  in 
the  former,  and  the  arrest  of  erosion  on  the  plateau  —  admits  of  only  one 
explanation.  While  rivers  and  rapid  ice-streams,  flowing  in  previously  ex- 
cavated valleys,  were  actively  engaged  in  deepening  these,  the  adjacent 
fjelds  were  buried  under  sheets  of  ne've'.  ...  In  short,  while  rivers  and 
glaciers  were  deepening  the  great  valleys  and  making  their  walls  steeper, 
the  intervening  mountain-heights  were  gradually  being  reduced  and  levelled 
by  denudation.  .  .  .  It -was  somewhat  otherwise  in  the  Alps,  where  the 
hydrographic  system,  perfectly  regular  in  preglacial  times,  was  only  slightly 
modified  by  subsequent  glacial  action.  Yet  even  there  erosion  proceeded 
most  rapidly  along  the  chief  lines  of  ice-flow.  Were  the  great  rock-basins 
of  the  principal  Alpine  valleys  pumped  dry,  we  should  find  the  mouths  or 
openings  of  the  side  valleys  abruptly  truncated,  and  their  waters  cascading 
suddenly  into  the  ice-deepened  main-valleys.  For,  as  Dr.  Wallace  has  shown, 
it  is  the  present  lake-surface,  not  the  lake-/fo//0w,  that  represents  approxi- 
mately the  level  of  the  preglacial  valley.  In  a  word,  erosion  proceeded  most 
actively  in  the  main-valleys,  the  bottoms  of  which  have  been  lowered  for 
several  hundred  feet  below  the  bottoms  of  the  side-valleys.  Precisely  the 


684  PHYSIOGRAPHIC  ESSAYS 

same  phenomena  are  repeated  in  Scotland.  Were  all  the  water  to  disap- 
pear from  the  Highland  lakes  and  sea-lochs,  we  should  find  waterfalls  and 
cascades  at  the  mouth  of  every  lateral  stream  and  torrent  (b,  246-249). 

It  is  evident  from  these  extracts  that  the  deepening  of  valleys 
is  regarded  as  greatest  where  lake  basins  have  been  eroded  be- 
neath the  pre-glacial  valley  floors ;  and  this  belief  is  explicitly 
expressed  in  the  following  extract  from  the  latest  edition  of 
the  same  author's  "  Great  Ice  Age,"  the  standard  work  on 
that  subject : 

Take  the  case  of  a  glacier  creeping  down  an  Alpine  valle\y  and  spread- 
ing itself  out  upon  the  low  ground  at  the  foot  of  the  moun 


ains.    Let  us 
wn  which  it 
moves  is  greater  than  the  slope  of  the  lower  reaches  of  the  vlalley.    When 


suppose  that,  in  the  upper  part  of  its  course,  the  incline  d 


the  glacier  attains  the  more  gently  inclined  part  of  its  course, 
that  its  flow  must  be  retarded,  and  there  will  therefore  be  a  te 


it  is  evident 
dency  in  the 


ice  to  accumulate  or  heap  up.  Now  we  know  that  the  pressure  of  a  body 
in  motion  upon  any  given  surface  varies  with  the  degree  at  which  that  sur- 
face is  inclined  ;  as  the  inclination  decreases  the  pressure  increases.  It 
follows  from  this  that  when  the  glacier  leaves  the  steeper  part  of  its  course, 
and  begins  to  creep  down  the  gentler  slope  beyond,  it  will  press  with  greater 
force  upon  its  rocky  bed,  and  this  increased  pressure  will  be  further  inten- 
sified by  the  greater  thickness  of  the  accumulated  ice.  .  .  .  The  result  of 
all  this  is  the  formation  of  a  rock-basin,  the  deeper  portion  of  which  lies 
towards  the  upper  end,  just  where  the  grinding,  force  of  the  glacier  is 
greatest  (a,  228,  229). 

It  seems  to  me  that  too  great  emphasis  is  here  placed  on  the 
erosion  accomplished  near  the  end  of  a  glacier,  as  indicated  by 
lakes,  and  not  enough  upon  the  deepening  of  the  valleys  up- 
stream from  terminal  lakes,  as  indicated  by  hanging  valleys.  It 
is  also  to  be  noted  that  De  Lapparent,  Richter,  and  J.  Geikie 
all  describe  the  hanging  valleys  of  Norway  as  if  their  pre-glacial 
form  had  not  been  significantly  changed,  thus  failing  to  bring 
clearly  forward  the  fact  that  the  valleys  of  to-day  are  the  ice 
channels  of  the  past,  and  that  the  larger  and  smaller  channels 
must  have  normally  discordant  floors  in  a  system  of  glacial 
drainage,  just  as  they  have  in  a  system  of  river  drainage, 
although  to  a  much  greater  degree.  The  full  analogy  between 
ice  and  water  channels,  which  throws  so  much  light  on  the 
whole  question  of  glacial  erosion,  was  first  clearly  set  forth  by 
the  two  following  observers. 


GLACIAL  EROSION  685 

Gannett  on  Lake  Chelan,  1898.  The  most  complete  statement 
of  the  general  principles  involved  in  the  production  of  hanging 
valleys  that  I  have  found  in  print  is  in  an  article  on  Lake  Chelan, 
in  the  Cascade  Mountains  of  Washington,  by  Henry  Gannett. 
Chelan  is  a  long  narrow  lake  occupying  the  distal  two  thirds  of 
the  deep  U-shaped  valley  of  the  Stehekin  river  on  the  eastern 
slope  of  the  mountains.  It  was  occupied  in  the  glacial  period 
by  a  heavy  ice  stream,  fifty  or  sixty  miles  long,  and  half  a  mile 
to  a  mile  broad.  The  rock,  walls  which  inclose  the  valley  are 
strikingly  parallel  to  one  another,  without  buttressing  spurs ; 
they  rise  from  4000  to  5000  feet  above  the  lake  waters.  Nearly 
all  the  streams  which  flow  into  the  valley  tumble  over  its  walls 
in  a  series  of  cascades.  "From  all  indications  it  appears  that  the 
ice  must  have  been  at  least  3000  feet  deep  in  this  gorge  of  the 
Stehekin,  since  several  of  the  smaller  branches  join  the  main 
glacier  at  that  height  above  its  bed." 

Speaking  of  these  features  in  a  more  general  way,  Gannett  says : 

A  glacier  is  a  river  of  ice,  and  it  behaves  almost  precisely  as  a  river  of 
water  does.  Its  effects  upon  its  channel  are  almost  precisely  similar  to 
those  of  a  river  upon  its  channel,  excepting  in  the  fact  that  all  its  opera- 
tions are  on  a  vastly  greater  scale.  ...  A  word  of  caution  must  here  be 
interpolated.  The  channel  of  a  river,  in  which  its  water  flows,  must  not  be 
confused  with  its  valley,  which  it  drains.  The  above  comparison  refers  to 
the  channel  of  a  river  [or  of  a  glacier],  not  to  its  valley.  .  .  .  The  glacier 
moves  down  the  gorge,  scouring  and  cutting  the  bottom  and  sides  as  it 
travels.  The  ends  of  the  mountain  spurs  are  planed  off  instead  of  being 
trimmed  to  sharp,  angular  points,  as  is  done  by  streams  in  gorges  cut  by 
them.  .  .  .  Where  the  main  glacier  is  joined  by  a  branch,  the  bed  of  the 
branch  is  commonly  found  to  be  at  a  higher  level  than  the  bed  of  the  main 
glacier,  because  being  larger  and  heavier  the  main  glacier  has  greater  cut- 
ting power  ;  indeed,  in  many  cases  the  beds  of  small  branches  are  hundreds, 
or  even  thousands,  of  feet  higher  than  that  of  the  main  glacier  to  which 
they  are  tributary.  The  parallelism  between  the  glacier  and  the  river  in 
their  channels  is  further  illustrated  by  this  fact.  The  surface  of  the  ice 
in  the  main  glacier  and  in  the  branch  must  have  been  at  the  same  level, 
although  the  bottoms,  as  stated  above,  differ  greatly  in  elevation.  So  it  is 
with  a  river  at  the  point  of  junction  of  branches.  The  surface  of  the  water 
must  be  practically  at  the  same  level  in  all  cases,  but  the  bottoms  of  the 
channels  differ  by  the  difference  in  depth  of  the  streams  at  their  point  of 
junction.  This  fact  affords  us  a  measure  of  the  minimum  thickness  of  the 
ice  at  any  place.  It  cannot  have  been  less  than  the  vertical  distance 


686  PHYSIOGRAPHIC  ESSAYS 

between  the  bed  of  the  main  glacier  and  that  of  the  tributary,  and,  indeed, 
must  in  all  cases  have  been  greater,  owing  to  the  thickness  of  the  tributary 
(417-428,  especially  418-420). 

Penck  on  Alpine  Valleys,  1899.  A  no  less  explicit  and  detailed 
statement  of  the  peculiar  features  of  glacial  channels  and  their 
relations  to  river  channels  was  made  by  Penck  at  the  meeting 
of  the  International  Geographical  Congress  in  Berlin,  September, 
1899.  The  discordance  of  lateral  and  main  valley  floors  was 
described  as  a  general  feature  of  all  the  larger  Alpine  valleys 
within  their  glaciated  areas.  The  possibility  of  explaining  the  dis- 
cordance by  faulting,  as  suggested  by  Rothpletz  lor  the  Linth- 
thal,  was  considered,  but  rejected.  The  contrasts  01  the  glaciated 
and  non-glaciated  Alpine  valleys  were  strongly  emphasized. 
The  excess  of  the  depth  in  the  main  valley  beneath  the  floor  of 
the  hanging  laterals  was  taken  as  a  minimum  measure  for  glacial 
erosion,  and  the  term  ''over-deepened,"  already  adopted  on 
earlier  pages  of  this  essay,  was  applied  to  valleys  thus  worn  to 
a  greater  depth  than  would  have  been  possible  to  normal  rivers. 
The  publication  of  Penck's  address  is  awaited  with  interest. 

Harker  on  Glacial  Valleys  in  Skye,  1899.  A  brief  article  by 
Harker  on  glaciation  in  Skye  describes  the  valleys  as  eroded  in 
massives  gabbros,  with  U-shaped  cross  section,  especially  in  the 
upper  stretches,  and  frequently  heading  in  a  corrie  whose  floor 
may  hold  a  small  rock-basin  tarn.  In  longitudinal  profile  the 
floor  of  a  valley  often  consists  of  two  of  three  stretches  of  rela- 
tively gentle  slopes,  or  sometimes  of  basin  form  and  then  hold- 
ing lakes,  separated  by  relatively  sudden  descents.  Tributary 
valleys  mouth  at  a  considerably  higher  level  than  the  floor  of 
the  main  valley  (196-199). 

Gilbert  on  Alaskan  Valleys,  1899.  A  valuable  contribution  to  the 
origin  of  hanging  valleys  will  be  found  in  a  report  on  the  Harriman 
Alaskan  Expedition  of  1899.  A  general  statement  of  results  was 
made  by  Gilbert  during  the  session  of  the  Geological  Society  of 
America  in  Washington,  December,  1899,  when  the  importance 
of  the  hanging  lateral  valleys  in  the  Alaskan  fiords,  and  their 
bearing  on  the  problem  of  glacial  erosion,  was  clearly  set  forth. 

Blanford  on  Scotch  Glens,  ipoo.  The  only  article  that  I  have 
found  on  hanging  valleys  in  Scotland  is  by  Blanford,  "On  a 


GLACIAL  EROSION  687 

Particular  Form  of  Surface,  apparently  the  Result  of  Glacial 
Erosion,  seen  on  Loch  Lochy  and  elsewhere."  The  "  particular 
form"  here  referred  to  is  the  smoothness  of  the  sides  of  the 
Great  Glen  of  Scotland,  a  feature  that  may  be  held  analogous 
to  the  smooth  rock  walls  of  the  Norwegian  fiords  and  to  the 
spurless  basal  cliffs  of  the  glaciated  Alpine  valleys.  It  is  in- 
ferred that  in  pre -glacial  time  the  streams  of  the  lateral  glens 
were  separated  by  advancing  spurs  which  buttressed  the  sides 
of  the  Great  Glen.  Now  the  spurs  seem  to  have  been  truncated, 
producing  the  smooth  and  even  sides  of  the  glen,  to  which 
attention  is  especially  directed.  The  lateral  glens  are  described 
as  at  present  opening  a  thousand  feet  above  the  floor  of  the 
Great  Glen,  whose  smoothed  sides  are  very  little  eroded  by  the 
descending  tributary  streams.  The  change  from  the  inferred 
pre-glajcial  form  is  conservatively  taken  to  indicate  a  glacial  ero- 
sion of  uat  least  250  or  300  feet  of  rock"  (198-204). 

Hershey  on  Sierra  Costa,  California,  ipoo.  An  article  by  Her- 
shey,  already  referred  to  above,  is  the  latest  contribution  to  the 
subject  in  hand.  In  following  up  a  valley  in  the  Sierra  Costa  in 
northwest  California,  it  is  at  first  V-shaped,  with  jagged  ledges 
between  sharp-cut  ravines  on  the  sides,  and  hardly  wider  at  the 
bottom  than  the  stream  that  drains  it.  On  reaching  the  stretch 
once  occupied  by  a  local  glacier,  the  valley  becomes  an  open  U- 
shaped  trough,  with  smooth  slopes  free  from  ravines  and  spurs. 
Above  the  limit  of  glacial  smoothing,  the  mountain  sides  are  still 
deeply  scored  with  ravines  and  jagged  with  outcropping  ledges. 
The  descent  of  a  glaciated  valley  floor  is  effected  by  a  series  of 
steps ;  the  stretches  of  more  gentle  fall  alternate  with  almost 
precipitous  falls  where  the  floor  is  let  down  several  hundred  feet. 
Corries  with  tarns  in  their  floors  are  well  developed  (42-57). 

Several  essays  by  Norwegian  authors  remain  to  be  considered. 
It  has  not  been  possible  to  make  reference  to  them  without 
postponing  the  appearance  of  this  paper,  and  consideration  of 
them  is  therefore  deferred  to  another  occasion. 

With  all  these  new  contributions  to  the  subject,  it  may  be 
expected  that  hanging  lateral  valleys  and  over-deepened  main 
valleys  will  soon  gain  the  importance  that  they  deserve  in  geo- 
graphical literature. 


688  PHYSIOGRAPHIC  ESSAYS 


REFERENCES 

Barrett,  R.  L.    "  The  Sundal  Drainage  System  in  Central  Norway."    Bull. 

Am.  Geog.  Soc.,  XXXII  (1900). 
Blanford,  W.  T.    "  On  a  Particular  Form  of  Surface,  apparently  the  Result 

of  Glacial  Erosion,  seen  on  Loch  Lochy  and  elsewhere."  Quart.  Jour. 

Geol.  Soc.,  LVI  (1900),  198-204. 
Boule,  M.     "  La  Topographic  Glaciaire  en  Auvergne."    Ann.  de  Geog.,  V 

(1896),  277-296.  \ 

Bruckner,  E.    "  Die  Vergletscherung  des  Salzachgebietei^."    Geog.  Abhand- 

lungeti,  I  (Vienna,  1885),  1-183. 


Davis,  W.  M.    "  Glacial  Erosion  in  the  Valley  of  the  Tic 


no."    Appalachia^ 


IX  (1900),  136-156. 

Forbes,  J.  D.    Norway  and  its  Glaciers.    Edinburgh,  185 
Forel,  F.  A.    "  Fleuves  et  Glaciers."    Bull.  Soc.  Vaud.  $ci.  ATat.,  XXXIII 

(1897),  202-204. 

Gannett,  H.     «  Lake  Chelan."    Nat.  Geog.  Mag.,  IX  (1898),  417-428. 
Geikie,  J.     (a)  The  Great  Ice  Age.     New  York,  3d  ed.,  1895. 

(b)  Earth  Sculpture.    London,  1898. 
Hall,  J.    Geology  of  New  York.     Part  IV,  comprising  the  geology  of  the 

fourth  district.      1843. 
Harker,   A.    "Glaciated  Valleys  in  the   Cuillins,   Skye."    Geol.  Mag.,  VI 

(1899),  196-199. 
Heim,  A.    (a}    Mechanismus  der  Gebirgsbildung.    Basel,  1878. 

(b}  "  Ueber  die  Erosion  im  Gebiete  der  Reuss."  Jahrb.  Schiv.  Alpenclub, 
^   XIV  (1879),  371-405- 
Hershey,  O.  H.    "Ancient  Alpine  Glaciers  of  the  Sierra  Costa  Mountains 

in  California."    Jour.  Geol.,  VIII  (1900),  42-57. 
Lapparent,  A.  de.    (a)  Legons  de  Geographic  Physique.  Paris,  ist  ed.,  1896. 

(b)  Lemons  de  Geographic  Physique.     Paris,  2d  ed.,  1898. 
Lubbock,  J.    The  Scenery  of  Switzerland.    New  York,  1896. 
Lugeon,  M.     "  LeQon  d'Ouverture  du  Cours  de  Geographic  Physique  pro- 

fesse  a  1'Universite  de  Lausanne."    Bull.  Soc.  Vaud.  Set.  Nat.,  XXXIII 

(1897),  49-78. 

Marr,  J.  E.     The  Scientific  Study  of  Scenery.     London,  1900. 
McGee,  W.  J.    (a}  "  Glacial  Canons."    Proc.  Am.  Assoc.  (1883),  238. 

(b)  "  Glacial  Canons."    Jour.  Geol.,  II  (1894),  350-364. 
Meunier,  S.    "  Sur  1' Allure  Gen^rale  de  la  Denudation  Glaciaire."    Coinptes 

Rendus,  CXXIV  (1897),  1043. 
Playfair,  J.  Illustrations  of  the  Huttonian  Theory  of  the  Earth.  Edinburgh, 

1802. 
Richter,  E.    "  Geomorphologische   Beobachtungen  aus  Norwegen."    Sitz- 

ungsber.  k.  k.Akad.  Wien,  Math.  Naturiv.  Classe,  CV,  Abth.  I  (1896), 

147-189. 


GLACIAL  EROSION  689 

Rothpletz,  A.  Das  geotektonische  Problem  der  Glarner  Alpen.    Jena,  1898. 
Russell,  I.  C.    "  Quaternary  History  of  Mono  Valley,  California."   U.S.Geol. 

Surv.,  VIII  Ann.  Rep.  (1889),  261-394. 
Rutimeyer,  L.     Ueber  Thai- und  See-Bildung.     Basel,  1869. 
Tarr,  R.  S.    "  Lake  Cayuga  a  Rock  Basin."    Bull.  Geol.  Soc.  Am.,  V  (1894), 

339-356. 
Wallace,   A.  R.  (a)  "The  Ice  Age  and  its  Work."  Fortnightly  Review, 

LX  (1893),  616-633,  75°-774. 
(b)  «  The  Gorge  of  the  Aar  and  its  Teachings."  Fortnightly  Review,  LXVI 

(1896),  175-182. 


XXV 

THE  OUTLINE  OF  CAPE  COD 

NOTE.  This  essay  attempts  to  restore  the  original  outline  of  Cape  Cod 
by  reversing  the  processes  at  work  on  the  present  outline.  In  order  to  gain 
good  understanding  of  these  processes,  a  review  of  previous  accounts  of 
the  Cape  is  introduced,  a  general  consideration  of  the  development  of  sea- 
shores is  outlined,  and  the  conclusions  reached  are  applied  to  the  problem 
in  hand.  It  is  thus  estimated  that  the  land  here  oice  extended  at  most 


two  or  more  miles  into  the  sea  on  the  east,  and  that 


perhaps  three  or  four 


thousand  years  have  been  required  for  the  retreat  o|f  the  shore-line  to  its 
present  position.  This  period  cannot,  however,  be  taken  as  a  full  measure 
of  the  time  since  the  glacial  deposits  of  the  Cape  were  formed,  for  there  is 
reason  to  believe  that  the  land  stood  higher  than  now  for  an  unknown 
interval  between  the  building  of  the  Cape  and  the  assumption  of  the  pres- 
ent attitude  with  respect  to  sea-level. 

The  chief  interest  in  the  problem  here  discussed  turns  on  the  growth  of 
the  great  sand  spit  of  the  "  Provincelands  "  northwestward  from  the  "  main- 
land "  of  the  Cape,  and  on  the  protection  thus  afforded  to  the  old  cliffs  of 
High  head.  Brief  account  is  given  of  the  growth  and  waste  of  the  Prov- 
incelands, and  of  the  changes  of  the  western  shore-line.  The  essay  closes 
with  some  practical  suggestions  regarding  the  protection  of  Provincetown 
harbor,  and  some  speculations  concerning  the  future  change  of  the  Cape. 
The  consumption  of  the  north  arm  —  from  the  elbow  to  the  hand  —  will 
probably  require  about  eight  or  ten  thousand  years. 

INTRODUCTION 

An  excursion  to  Provincetown  and  the  "  mainland  "  of  Truro 
on  Cape  Cod. with  the  students  of  the  Harvard  summer  course 
in  physical  geography,  in  July,  1895,  brought  to  my  attention  a 
number  of  problems  concerning  the  changes  of  outline  suffered 
by  the  Cape.  These  problems  had  taken  rough  shape  on  the 
occasion  of  a  visit  to  the  peninsula  several  years  ago.  Supple- 
menting the  observations  made  on  the  ground  by  a  study  of  the 
Coast  Survey  charts  and  by  a  review  of  what  has  been  written 
on  the  subject,  this  essay  has  gradually  grown  up.  Its  substance 
was  presented  before  the  Geological  Society  of  America  at  the 

690 


THE  OUTLINE  OF  CAPE  COD  691 

winter  meeting  in  Philadelphia,  December,  1895,  and  again  before 
the  Harvard  Geological  Conference  in  April,  1896. 

The  end  of  the  Cape  is  pleasantly  reached  by  a  four-hour  run 
in  a  steamboat  from  Boston  across  Massachusetts  bay  to  Prov- 
incetown,  in  whose  neighborhood  the  most  significant  of  the 
features  here  described  are  to  be  found.  By  driving  to  High 
head,  the  northernmost  point  of  the  "  mainland,"  a  general  view 
of  the  peninsula  of  Provinceland  may  be  gained  ;  thence  driving 
or  walking  to  Highland  light,  one  may  see  a  portion  of  the  long 
harborless  cliff  that  forms  the  "back,"  or  eastern  side,  of  the 
Cape.  Walking  northwestward  along  the  beach  to  Peaked  hill 
life-saving  station,  the  action  of  the  surf  can  be  observed  at 
leisure  ;  and  thence  crossing  the  sandy  belt  to  Provincetown, 
the  varied  forms  of  the  dunes  can  be  studied  in  detail.  A  sec- 
ond day  may  well  include  a  visit  to  Race  point,  the  northwest- 
ern extremity  of  the  Cape,  and  a  return  southward  along  the 
wasting  shore  to  Wood  end,  or  Long  point,  whence  the  town 
can  be  regained  by  boat,  previously  arranged  for. 

Cape  Cod  is  an  excellent  region  for  the  study  of  shore-forms 
in  the  light  of  their  development  from  some  antecedent  outline, 
and  their  continued  change  towards  some  future  state.  Although 
the  mainland  of  the  Cape  rises  about  two  hundred  feet  above 
sea-level,  it  is  built  of  uncompacted  clays  and  sands,  with  occa- 
sional bowlders,  and  is  therefore  easily  consumed  by  the  waves. 
Standing  far  out  beyond  the  general  shore  of  New  England,  it 
receives  a  violent  attack  from  storm  waves,  which  alter  the 
shore-line  so  rapidly  that  the  changes  are  measurable  even  in 
the  short  time  covered  by  our  records. 

EXTRACTS  FROM  PREVIOUS  WRITINGS 

The  following  extracts  summarize  a  number  of  previous  ref- 
erences to  the  Cape  : 

In  the  "Geology of  Massachusetts"  ( 1 84 i),E.  Hitchcock  makes 
brief  mention  of  the  erosion  on  the  eastern  coast  and  the  growth 
of  the  Cape  into  Massachusetts  bay  (323),  the  southward  growth 
of  Nauset  beach,  a  mile  in  fifty  years  (324),  the  dunes  of  Prov- 
incetown (325),  and  the  "diluvial  elevations  and  depressions" 


692  PHYSIOGRAPHIC  ESSAYS 

of  Truro  (367);  Provihceland  is  "alluvial;  that  is,  washed  up 
by  the  ocean  "  (371). 

Lieutenant  (afterwards  Admiral)  C.H.  Davis  wrote  a  "  Memoir 
upon  the  Geological  Action  of  the  Tidal  and  Other  Currents  of  the 
Ocean,"  in  which  he  called  attention  to  the  repeated  occurrence 
along  our  coast  of  bars  built  northward  from  coastal  bluffs,  such 
as  Sandy  Hook,  New  Jersey,  and  Cape  Cod,  and  suggested  that 
"a  generic  term"  should  be  applied  to  these  forms.  He  men- 
tioned a  place  of  division  of  the  tidal  currents  on  the  east  side 
of  Cape  Cod,  near  Nauset  inlet,  from  which  the  flood  tide  flows 
north  and  south. 

Thoreau's  narrative  of  his  excursions  on  the  Cape  in  1849, 
1850,  and  1855  tells  of  various  changes  in  tpe  coast  line  known 
to  the  people  there.  A  log  canoe,  buried  long  before  on  the 
inner  side  of  the  bar  that  forms  the  eastern  wall  of  the  marshy 
East  harbor  at  the  north  end  of  the  mainland,  was  found  many 
years  afterwards  on  the  Atlantic  side  of  the  bar ;  that  is,  the 
bar  had  been  pushed  westward  over  the  buried  canoe  as  the  sea 
cut  away  the  outer  beach.  Swamp  peat  was  sometimes  found 
on  the  exposed  beach,  although  it  was  originally  formed  un- 
doubtedly on  the  inside  of  the  bar.  Stumps  had  been  seen  off 
Billingsgate  point ;  the  implication  being,  not  that  the  land  had 
been  depressed,  but  that  it  had  been  washed  away,  leaving  the 
stumps  mired  in  their  native  soil.  I  have  found  this  explanation 
of  the  occurrence  of  tree  stumps  on  the  shoals  of  Chatham  cur- 
rent among  the  fishermen  of  the  Cape.  A  writer  in  the  Mas- 
sachusetts Magazine  of  the  previous  century  is  quoted  to  the 
effect  that  an  island,  called  Webbs  island,  formerly  existed  three 
leagues  off  Chatham,  containing  twenty  acres  of  land ;  the  people 
of  Nantucket  carried  wood  from  it ;  but  in  the  writer's  day  a 
large  rock  alone  marked  the  spot,  and  the  water  thereabouts 
was  six  fathoms  deep  (182,  183). 

Freeman's  "History  of  Cape  Cod"  (1860)  attributes  much 
wasting  of  land  to  reckless  cutting  of  the  trees,  —  a  doubtful 
conclusion  as  far  as  it  refers  to  shore  work,  although  probably 
applicable  to  the  interior  district  of  the  dunes.  He  says  : 

The  work  of  devastation  was  too  extensively  accomplished  ;  as  is  seen 
on  the  shores  of  the  Cape  since  washed  away  by  tides  aided  by  the  force 


THE  OUTLINE  OF  CAPE  COD  693 

of  the  winds,  so  that  vast  flats  of  sand  extend  in  some  places  a  mile 
from  the  shore,  now,  at  low  water,  dry,  or  nearly  so,  and  in  some  instances 
these  flats  disclose  large  stumps  of  ancient  trees  embedded  in  their  native 
peat  (752). 

H.  L.  Whking  prepared  a  "  Report  on  the  Special  Study  of 
Provincetown  Harbor,  Massachusetts."  He  distinguishes  Truro- 
land,  the  mainland  of  the  Cape,  "  by  the  existence  of  clay  and  of 
bowlders,  and  by  the  peculiar  form  of  the  '  bowl  and  dome ' 
drift";  and  Provinceland,  "  of  sand  only,  —  so  free  from  all 
earthy  matter  that  it  will  not  even  discolor  water,  —  while  the 
forms  which  the  dunes  and  ridges  here  assume  are  mainly 
characteristic  of  wind  drift  "(15 5).  He  concludes  that 

the  outer  ridges  of  the  peninsula  of  Provincetown  were  the  earliest  in  date, 
and  that  the  flats,  marshes,  and  ponds  now  existing  are  subsequent  accumu- 
lations and  accidents,  which  have  taken  place  under  the  shelter  and  eddy 
influences  of  the  outer  hooked  bar  or  beach  (155). 

The  narrow  outer  bar  that  connects  the  cliffs  of  Highland  light 
with  the  Provincetown  peninsula  is  described  as  wasting  back 
with  the  cliffs,  and  is  said  to  be  in  danger  of  breaking  through 
at  two  points. 

H.  Mitchell  wrote  a  "  Report  .  .  .  concerning  Nausett  Beach 
and  the  Peninsula  of  Monomoy."  Monomoy  is  described  as  built 
of  sands  derived  from  the  bluff  of  Cape  Cod  during  northeast 
storms ;  it  grew  southward  into  Nantucket  sound  at  the  rate  of 
one  hundred  and  fifty-seven  feet  a  year  from  1856  to  1868. 
The  changes  in  the  beach  near  Chatham  are  particularly  de- 
scribed. The  same  author  submitted  an  "Additional  Report  on 
the  Changes  in  the  Neighborhood  of  Chatham  and  Monomoy." 

W.  Upham  published  some  notes  on  Cape  Cod  in  the  "Geology 
of  New  Hampshire"  (1878),  and  a  more  extended  essay  on  "The 
Formation  of  Cape  Cod"  a  year  later.  He  described  the  moraine 
extending  eastward  from  Sandwich  and  entering  the  sea  at  Or- 
leans (494);  north  of  this  point  the  Cape  consists  chiefly  of 
modified  drift,  rarely  containing  bowlders  (537).  When  the  drift 
plains  were  deposited,  the  land  stood  somewhat  higher  than  at 
present  (561).  Provinceland  consists  of  sea  sand,  supplied  by 
erosion  on  the  east  side  of  the  Cape  (564). 


694  PHYSIOGRAPHIC   ESSAYS 

Chamberlin  makes  a  brief  reference  to  Cape  Cod  in  his  essay 
on  the  "  Terminal  Moraine  of  the  Second  Glacial  Epoch." 

The  great  northward  hook  of  Cape  Cod  is  composed  of  plains  and  rolling 
hills  of  sand  and  gravel,  which  resemble  accumulations  that  often  accom- 
pany the  morainic  belt  on  its  interior  side,  and  suggest  the  thought  that 
the  hook  may  be  the  modified  inner  border  of  the  moraine  which  enters  the 
sea  near  Orleans,  and  may  be  presumed  to  curve  northward  concentric  with 
the  hook,  forming  thus  a  loop  inclosing  the  basin  of  Cape  Cod  (379). 

H.  L.  Marindin  studied  the  "  Encroachment  of  the  Sea  upon 
the  Coast  of  Cape  Cod,  Massachusetts  \(a).  From  Highland 
light  to  Nauset  lights  the  average  recessio\i  from  1848  to  1888 
was  128  feet,  or  3.2  feet  per  annum.  The  face  of  the  cliff, 
whose  average  height  is  50  or  100  feet,  has  thus  lost  a  total  of 
30,231,038  cubic  yards,  or  755,776  cubic  yards  per  annum.  The 
bar  south  of  Nauset,  inclosing  the  north  side  of  Pleasant  harbor, 
extended  its  length  southward  some  distance  in  the  same  period. 
The  same  author  has  made  a  detailed  report  on  the  changes  in 
shore-line  and  anchorage  areas  of  Provincetown  harbor  (^). 

K.  Weule  has,  in  his  •"  Beitrage  zur  Morphologic  der  Flach- 
kiisten,"  discussed  Cape  Cod  at  some  length  (232-238).  The 
tidal  currents  are  regarded  as  the  most  important  factors  in 
its  shaping.  A  misunderstanding  of  local  conditions  is  implied 
when  the  author  asks  how  "  the  narrow  mainland  of  uncom- 
pacted  materials  can  remain  intact  in  an  exposed  situation,  when 
even  so  resistant  landmasses  as  rocky  Nantucket  and  Martha's 
Vineyard  suffer  great  loss  "  (232).  The  present  preservation  of 
the  Cape  is  ascribed  to  the  beach  sand,  brought  from  the  shoals 
on  the  southeast  by  the  flood  tide.  Weule  follows  Whiting  in 
attributing  a  greater  age  to  the  outer  than  to  the  inner  side  of 
Provincetown  peninsula  (234).  The  existing  mainland  is  regarded 
as  only  a  remnant  of  a  great  extent  of  drift  land  (233) ;  this 
opinion  being  taken  from  a  report  by  A.  Agassiz. 

A  brief  article  of  my  own,  describing  "  Facetted  Pebbles  on 
Cape  Cod,"  argued  from  these  evidences  of  aeolian  action  that 
the  plains  of  gravel  and  sand  were  deposited  under  the  air 
rather  than  under  the  sea. 

A  "Report  of  the  Trustees  of  Public  Reservations  on  the 
Subject  of  the  Province  Lands  "  (6)  states  that  "  there  is  evidence 


THE  OUTLINE  OF  CAPE  COD  695 

that  the  tides  and  waves  have  built  one  beach  after  another,  each 
farther  north  than  the  last,  and  that  the  so-called  Peaked  hill  bar 
is  a  new  beach  now  in  process  of  formation."  The  report  contains 
an  elaborate  map  of  the  sandy  peninsula  by  J.  N.  McClintock, 
on  a  scale  of  about  five  inches  to  a  mile,  with  ten-foot  contours. 
The  manner  in  which  the  outer  beaches  overlap  the  inner  ones 
is  very  clearly  shown.  Five  photographic  illustrations  present 
characteristic  views  of  the  dunes. 

A  general  work  on  coastal  forms  —  "  La  Geographic  Littorale" 
-by  J.  Girard,  briefly  compares  Sandy  Hook  and  the  end  of 
Cape  Cod,  classifying  them  with  spits  formed  by  littoral  cur- 
rents, but  giving  no  specific  description. 

The  structures  of  the  mainland  of  Truro  and  of  the  pen- 
insula of  Provinceland  are  so  unlike  that  their  different  origins 
have  long  been  recognized  ;  the  former  being  attributed  chiefly 
to  diluvial  or  glacial  and  aqueo-glacial  agencies,  the  latter  to 
marine  agencies  acting  on  the  former.  The  general  character  of 
existing  processes  by  which  the  shores  are  undergoing  change 
and  the  present  rate  of  action  of  these  processes  have  been 
carefully  examined  by  various  observers ;  but  no  systematic 
attempt  has  been  made  to  trace  the  processes  and  the  changes 
that  they  have  produced  backward  to  their  beginning.  This 
task  is  therefore  attempted  here. 

RECONSTRUCTION  OF  THE  ORIGINAL  OUTLINE  OF  THE  CAPE 

The  development  of  the  existing  outline  of  Cape  Cod  must 
be  traced  backward  to  the  original  outline.  The  initial  form 
that  it  had  before  the  present  cycle  of  cutting  and  filling  began 
along  its  shores  may  be  roughly  reconstructed  by  reversing 
the  marine  processes  now  at  work  and  following  them  until  they 
lead  back  through  earlier  and  earlier  conditions.  The  restora- 
tion may  be  regarded  as  complete,  when  the  reconstructed  forms 
are  everywhere  of  non-marine  origin.  Then,  reversing  the  order 
of  study,  the- normal  operation  of  cutting  and  filling  processes 
should  lead  forward  again  to  the  existing  outline  of  the  Cape, 
and  should  even  allow  a  reasonable  prediction  of  future  changes 
for  some  time  to  come. 


696 


PHYSIOGRAPHIC  ESSAYS 


Provinceland,  the  Chatham  bars,  Monomoy,  and  a  few  small 
bars  near  Wellfleet  must  first  be  removed,  as  they  consist 
wholly  of  sea-carried  materials,  their  arrangement  being  closely 
accordant  with  action  at  present  sea-level.  The  tidal  marshes 
north  of  Wellfleet,  along  Pamet  river,  and  elsewhere,  should  be 
excavated.  The  mainland,  chiefly  of  glacial  and  aqueo-glacial 


FIG.  107 

deposits,  will  then  stand  out  alone,  as  indicated  by  the  outline 
NBHQPTC  (Fig.  107).  It  descends  to  the  shore  on  nearly  all 
sides  in  steep  cliffs  of  moderate  height ;  long,  straight,  or  gently 
curving  beaches  running  along  the  base  of  the  cliffs.  Excep- 
tions to  this  rule  are  found  almost  exclusively  on,  the  shores  of 
protected  bays,  such  as  those  north  of  Chatham  and  about 
Wellfleet.  The  cliffed  descent  of  the  mainland  to  the  smooth 
beaches  is  manifestly  an  indication  of  destructional  retreat  from 


THE  OUTLINE  OF  CAPE  COD  697 

a  formerly  greater  extension  seaward,  just  as  the  gentle  slope 
of  the  land  to  the  irregular  shore-line  of  the  bays  is  an  indica- 
tion of  small  change  from  constructional  form. 

Although  no  close  accuracy  is  to  be  expected  in  restoring  the 
seaward  extension  of  the  cliffed  mainland,  there  are  nevertheless 
some  simple  principles  that  will  at  least  serve  to  guide  us  towards 
a  not  altogether  imaginary  reconstruction.  First,  it  must  be  re- 
membered that  general  sub-aerial  denudation  has  not  effected 
significant  changes  in  glacial  topography  during  post-glacial  time  ; 
second,  the  restored  outline  should  possess  irregularities  of  pat- 
tern comparable  to  those  in  the  protected  bays  of  to-day,  advanc- 
ing from  the  headlands  and  retreating  towards  the  troughs  or 
"  valleys  "  in  the  high  ground  ;  third,  the  amount  of  land  restored 
should  be  much  less  on  protected  shores  than  on  exposed  shores  ; 
fourth,  cliffs  that  are  now  protected  by  forelands  of  marsh  and 
bar  must  not  be  built  out  so  far  that  their  recession  could  not 
have  been  accomplished  before  the  bars  began  to  grow  in  front 
of  them. 

POSSIBLE  CHANGES  OF  LEVEL 

These  four  guiding  principles  do  not  include  reference  to  the 
effects  of  change  of  level,  because,  if  any  change  has  occurred 
since  the  time  of  accumulative  construction  of  the  mainland,  it 
has  been  of  small  amount,  and  it  has,  to  my  mind,  acted  on  the 
whole  in  favor  of  decreasing  the  land  area  by  submergence,  thus 
cooperating  with  the  destructive  action  of  the  sea.  This  view  is 
in  accord  with  that  expressed  by  Upham,  who  thinks  that,  when 
the  drift  was  deposited  hereabouts,  the  land  stood  somewhat 
higher  than  at  present,  and  that  the  numerous  small  indentations 
or  reentrants  of  the  shore-line,  such  as  occur  along  the  south 
side  of  the  Cape,  are  results  of  a  slight  submergence  of  trough- 
like  depressions  or  valleys.  The  digitate  bays  of  Marthas  Vine- 
yard would  seem  to  lend  support  to  this  view ;  but  they  were 
otherwise  interpreted  by  Professor  Shaler,  who  regarded  them  as 
having  been  formed  by  sub-glacial  streams  acting  on  sea-floor 
deposits  that  had  been  strewn  in  front  of  the  ice  margin  when 
the  sea  stood  higher  than  now,  although  he  suspected,  also,  that 
"at  the  close  of  the  glacial  period  this  region  was  considerably 


698  PHYSIOGRAPHIC  ESSAYS 

higher  than  at  present  "  (318,  319,  350).    The  latter  view  is  further 
supported  by  the  small  amount  of  erosion  —  about  three  miles  — 
suffered  by  the  low,  sandy,  southern  shore  of  Marthas  Vineyard 
(349)  since  the  present  level  of  the  land  was  assumed. 

Without  undertaking  to  determine  precisely  the  original  level 
of  the  Cape  mainland,  the  most  plausible  explanation  of  the  facts 
seems  to  me  that  the  washed  gravels  and  sands  correspond 
to  the  supermarine  sandr  of  Greenland  and  Alaska  ;  that  the 
troughs,  by  which  the  plains  of  washed  sands  are  trenched,  re- 
sult from  the  channeling  by  streams  wnen  they  carried  less  waste 
than  while  they  were  previously  aggrading  the  plains  ;  and  that 
the  indentations  of  the  shore-line  are  the  result  of  slight  depres- 
sion, whereby  the  troughs  were  partly  drowned.  The  recon- 
struction of  what  I  have  above  called  the  "  original  outline"  will 
therefore  not  necessarily  lead  us  to  the  shore-line  that  obtained 
at  the  close  of  the  time  of  accumulative  construction,  if  the  land 
then  stood  higher  than  now  ;  but  only  to  a  contour  line  drawn 
on  the  original  constructional  mainland  at  present  sea-level. 
However,  between  the  actual  original  shore-line  and  the  recon- 
structed contour  line  there  must  have  been  a  difference  of 
degree  rather  than  of  kind  ;  the  latter  embracing  a  smaller  land 
area  than  the  former,  but  the  general  outline  and  disposition  of 
the  land  areas  probably  being  of  much  the  same  style  in  both 
cases,  except  for  the  indentations  of  drowned  valleys  after  sub- 
mergence. For  this  reason  no  further  especial  attention  will 
be  given  to  depression  in  its  effect  in  altering  the  outline  of 
the  Cape. 

A  proposed  reconstruction  of  the  outline  of  the  Cape  has  been 
drawn,  with  the  four  guiding  principles,  above  stated,  in  mind. 
Trifling  additions  are  made  in  the  bays  ;  none  more  than  two 
thousand  feet.  Significant  additions  are  made  on  the  west  side 
of  the  Cape  ;  some  of  these  measure  four  thousand  or.  five  thou- 
sand feet.  Two  miles  or  more  of  land  are  added  on  the  east  side, 
or  "  back,"  facing  the  broad  Atlantic.  The  margin  of  the  restored 
outline  is  indented  toward  the  various  troughs  and  valleys  that 
break  the  general  surface  of  the  mainland.  About  High  head, 
the  northern  point  of  the  cliffed  mainland,  the  fourth  of  the 
guiding  principles  comes  into  play ;  and  hereabouts  the  most 


THE  OUTLINE  OF  CAPE  COD  699 

interesting  problem  of  the  Cape  is  found.  The  view  of  the  pen- 
insula of  Provinceland  from  this  commanding  point  is  therefore 
particularly  instructive. 


THE  PROBLEM  OF  HIGH  HEAD 

The  cliffed  margin  of  the  mainland  at  High  head,  H  (Fig.  107), 
is  notably  even  both  on  the  northern  and  western  sides.  At  pres- 
ent the  head  is  protected  both  on  the  west  and  north  by  forelands 
of  marsh  and  bar,  the  bars  springing  tangent  from  cliff  fronts 
farther  south  or  southeast.  The  bar,  QR,  on  the  west  is  part  of 
a  long,  concave  shore-line,  TPQR, — the  "west  concave"  shore, 
—  whose  excavated  curve  is  manifestly  dependent  on  the  exist- 
ence of  the  peninsula  of  Provinceland  to  the  northwest.  Before 
this  concave  curve  was  cut,  a  nearly  straight  shore-line,  CTVQH, 
-  the  "  west  straight  "  shore,  —  had  been  made,  as  indicated  by 
its  remnants  now  seen  on  the  west  marginal  cliff,  QH,  of  High 
head,  and  again  about  six  miles  to  the  south,  TC,  on  Boundbrook, 
Griffins,  and  other  islands.  The  cutting  of  the  west  straight  cliff, 
QH,  must  have  continued  until  the  peninsula  of  Provinceland 
began  to  project  northwest  to  High  head.  Then,  as  the  move- 
ment of  the  shore  currents  \vas  somewhat  changed  by  the  inter- 
ference of  the  peninsula,  the  middle  of  the  straight  cliff  was 
excavated  more  rapidly,  forming  the  west  concave  shore,  TPQ, 
and  the  northern  part  of  the  straight  cliff  on  High  head  at  the 
same  time  came  to  be  protected  by  the  outspringing  concave 
bar,  QR,  that  now  incloses  East  harbor  and  its  marshes  on 
the  southwest  side. 

The  bar,  2?/,  on  the  north  of  High  head  is  part  of  the  long 
eastern  convex  shore-line,  NBJK,  whose  form  is  determined  by 
the  masterly  Atlantic  currents.  It  is  along  the  outer  beach  of 
this  bar  —  or  of  its  representative  in  former  days  —  that  the 
sands  of  the  peninsula  have  been  transported  from  the  south- 
east ;  this  being  the  conclusion  of  all  observers,  unless  perhaps 
of  Hitchcock.  Now  it  follows  from  the  relation  of  this  northeast 
bar  to  the  peninsula  of  Provinceland,  and  from  the  relation  of 
the  peninsula  to  the  western  bar,  that  a  somewhat  shorter  time 
was  allowed  for  cutting  the  north  cliff  of  High  head  than  for 


700  PHYSIOGRAPHIC   ESSAYS 

cutting  its  west  cliff ;  but  inasmuch  as  wave  energy  was  greater 
on  the  north  than  on  the  west,  time  and  energy  varied  inversely, 
and  hence  about  the  same  amount  of  lost  land  may  be  added  to 
each  cliff.  The  amount  of  reduction  suffered  on  either  side  of 
High  head  is  therefore  roughly  proportional  to  the  time  before 
the  bar  was  built  in  front  of  the  norm  cliff. 

The  north  bar,  BJ,  which  for  this  reason  takes  our  attention,  is 
one  of  the  class  built  by  marine  action,  as  recognized  by  Admiral 
Davis.  It  springs  tangent  to  the  curve  of  the  long  convex  cliff 
and  beach,  7V7?,  on  the  east  side,  or  r  back,"  of  the  Cape.  As  the 
retreat  of  the  margin  of  High  head  is  measured  by  the  time 
before  the  north  bar  was  built,  the  question  arises  whether  bars 
of  this  kind  are  built  in  front  of  straight  cliffs  early  or  late  in 
the  attack  made  by  the  sea  on  the  land.  This  question  may 
be  divided  into  two  :  the  first  considering  the  development  of 
the  cliff ;  the  second  considering  the  stage  in  the  development 
of  the  cliff  when  the  protecting  bar  would  be  likely  to  grow 
out  in  front  of  it. 


DEVELOPMENT  OF  SHORE  PROFILES 

Let  the  activities  of  the  sea  be  resolved  into  two  components: 
one  acting  on  and  off  shore,  the  other  along  shore  ;  and  let  the 
effects  of  the  first  of  these  components  be  now  examined  alone, 
postponing  consideration  of  the  effects  of  the  second  component 
to  the  next  section. 

On  some  young  coasts  the  on-and-off-shore  movements  of  the 
sea  carry  out  to  deep  water  all  of  the  waste  that  is  abraded  from 
the  land  and  its  submarine  slope,  leaving  the  shore-line  bare. 
The  rocky  floor  seen  at  low  tide  on  the  coast  of  Brittany  illus- 
trates this  condition.  Here  the  sea  is  able  to  do  more  work  than 
it  has  to  do.  Its  action  is  like  that  of  a  young  river,  whose  ability 
to  carry  load  is  greater  than  the  resistance  of  the  load  that  it  has 
to  carry,  and  whose  valley  floor  is  therefore  attacked  and  deep- 
ened. But  as  the  valley  is  deepened,  the  slope,  velocity,  and 
carrying  power  of  the  river  are  all  decreased ;  at  the  same  time, 
the  load,  derived  chiefly  from  the  valley  slopes,  is  increased ; 
thus  ability  to  do  work  gradually  falls  into  equality  with  the 


THE  OUTLINE  OF  CAPE  COD  701 

work  to  be  done.  When  this  happy  condition  is  reached,  the 
river  may  be  said  to  have  graded  its  channel.  Youth  then  passes 
into  adolescence. 

A  comparable  series  of  changes  may  be  detected  in  studying 
the  profile  of  a  seacoast  at  right  angles  to  the  general  shore-line. 
As  the  sea  can  at  first  usually  dispose  of  more  waste  than  it 
gathers,  the  coast  is  energetically  attacked  and  forced  to  retreat, 
and  sea  cliffs  are  thus  produced.  But  in  virtue  of  the  changes 
thus  brought  about,  the  energy  of  on-and-off-shore  attack  de- 
creases, while  the  waste  coming  from  the  growing  cliffs  increases ; 
thus  ability  to  do  work  approaches  equality  with  work  to  be  done, 
and  the  sea-floor  profile,  like  that  of  the  valley  floor,  may  be  said 
to  be  graded.  When  a  graded  profile  is  attained,  the  adolescent 
stage  of  shore  development  is  reached. 

The  amount  of  retreat  necessary  before  a  graded  profile  is 
attained,  varies  with  the  texture  of  the  coast,  and  with  its  expo- 
sure to  the  sea.  A  coast  of  unconsolidated  deposits  will  soon 
supply  a  large  amount  of  waste  from  its  cliffed  margin,  while  the 
cliffs  of  a  rock-bound  coast  will  shed  waste  slowly  ;  hence,  on 
coasts  of  given  exposure,  grade  will  be  assumed  with  a  less 
amount  of  cliff-cutting  where  the  rocks  are  weak  than  where 
they  are  strong.  This  recalls  the  behavior  of  rivers  in  regions  of 
weak  and  resistant  rocks  ;  in  the  latter  they  may  assume  gentle 
slopes  ;  but  in  the  former  rather  steep  slopes  are  necessary  to 
carry  off  the  freely  offered  waste  ;  and  gentler  slopes  can  be 
assumed  only  as  the  whole  surface  is  worn  down ;  this  general 
relation  having  been  pointed  out  some  years  ago  by  Major 
Powell  (uUinta  Mountains,"  194).  Moreover,  inasmuch  as  a 
greater  amount  of  waste  can  be  handled  on  exposed  coasts  than 
on  protected  coasts,  a  considerable  retreat  may  develop  high 
cliffs  on  the  former  before  enough  waste  is  shed  from  the  cliff 
face  to  give  the  shore-waves  all  the  work  they  can  do  ;  while 
on  protected  coasts  a  moderate  retreat,  producing  low  cliffs,  will 
supply  as  much  waste  as  can  be  handled  by  the  sea. 

The  under-water  form  of  a  graded  profile,  when  first  developed, 
also  depends  largely  on  the  violence  of  the  on-and-off-shore  move- 
ments of  the  sea.  On  a  protected  coast  the  bottom  will  be  de- 
graded so  as  to  descend  from  the  shore-line  by  a  gentle  slope  to 


702  PHYSIOGRAPHIC  ESSAYS 

an  eroded  platform  of  moderate  depth  ;  but  on  an  exposed  coast 
the  bottom  will  be  degraded  so  as  to  descend  from  the  shore-line 
by  steeper  slope  to  a  platform  of  greater  depth. 


TYPICAL  SHORE  PROFILES 

/ 
A  graded  profile  being  once  attained,  its  graded  condition  will 

be  preserved  through  all  the  res/t  of  an  undisturbed  or  normal 
cycle  of  shore  development  ;  snore  profiles  and  river  profiles 
being  alike  in  this  as  in  so  ma^ny  other  respects.  Before  grade 
is  assumed,  the  ability  of  the  sea  may  be  so  far  in  excess  of  its 
load  that  it  under-cuts  the  shore  and  forms  sea  caves  at  tide  level, 
as  in  profile  I  (Fig.  108).  When  grade  is  first  assumed,  the  coast 
is  usually  cut  back  to  a  steep  cliff,  like  profile  2.  Much  later, 


FIG.  1 08 

when  the  sea  has  cut  back  the  shore  so  that  the  waves  must 
traverse  a  submarine  platform  before  attacking  the  land,  their 
strength  is  thereby  so  much  lessened  that  the  cliff  leans  back  to 
a  moderate  slope,  as  in  profiles  3  and  4,  and  even  then  supplies 
enough  waste  to  keep  the  waves  at  its  foot  fully  occupied. 

There  is  something  more  than  analogy  in  the  comparison  that 
may  be  drawn  between  the  longitudinal  profile  of  a  stream  and 
the  transverse  profile  of  a  shore.  In  youth  each  usually  has  its 
torrent  or  upper  portion,  where  ability  to  carry  load  is  greater 
than  load  to  be  carried ;  but  as  development  progresses,  the 
graded  condition  of  midstream  extends  headward,  and  after  a 
time  reaches  all  the  way  to  the  headwaters.  At  the  same  time, 
the  lower  or  flood-plain-delta  portion  extends  seaward,  its  grade 
being  rather  steeper  in  adolescence,  when  much  material  is 
brought  from  the  headwaters,  than  later,  in  maturity  and  old 
age,  when  the  supply  of  waste  is  very  slow.  The  critical  point, 
where  marine  action  changes  from  degrading  the  near-shore 


THE  OUTLINE  OF  CAPE  COD  703 

bottom  to  aggrading  the  off-shore  bottom,  migrates  seaward,  as 
i',  2',  3',  4',  in  Fig.  1 08.  At  the  same  time,  the  seaward  extension 
of  the  bottom  deposits  increases.  Furthermore,  the  comparison 
between  stream  and  sea  suggests  the  need  of  examining  that 
process  on  the  sea  floor,  which  corresponds  to  corrasion  in  the 
stream  bed.  Sea-shore  profiles  make  it  clear  that  a  considerable 
deepening  is  accomplished  on  the  floor  of  the  platform,  landward 
from  the  critical  points  i',  2',  etc.  Off  the  eastern  cliff  of  Cape 
Cod  this  deepening  can  hardly  have  been  less  than  fifteen  or 
twenty  fathoms  ;  off  the  Chalk  cliffs  of  Normandy  a  similar 
scouring  and  deepening  of  the  bottom  may  be  inferred.  We  are 
accustomed  to  study  transportation  and  deposition  as  submarine 
processes,  but  little  attention  has  been  given  to  decomposition, 
disintegration,  corrasion,  or  any  other  process  by  which  the  sea 
floor  is  degraded.  The  subject  deserves  careful  investigation. 

It  is  manifest  from  the  preceding  paragraphs  that  a  graded 
profile  may  be  attained  much  earlier  on  one  part  of  a  shore-line 
than  on  another ;  for  the  texture,  the  original  profile,  and  the 
exposure  of  a  coast  all  vary  from  place  to  place.  But  in  a  region 
like  Cape  Cod,  where  the  original  shore-line  consisted  wholly  of 
uncompacted  materials,  this  aspect  of  the  problem  need  not  be 
considered  further. 


DEVELOPMENT  OF  SHORE  OUTLINES 

It  is  not,  however,  only  in  on-and-off -shore  action  that  a  close 
comparison  may  be  drawn  between  the  operations  of  marine  and 
fluviatile  agencies.  The  longshore  action  of  the  sea  also  is  in 
many  respects  comparable  to  the  downstream  action  of  rivers. 
Beginning  on  an  unevenly  deformed  land  surface  in  a  region  of 
moderate  rainfall,  where  there  are  many  heights  and  hollows,  the 
drainage  will  at  first  consist  of  many  small  independent  systems, 
each  one  transporting  waste  from  the  initial  divides  down  the 
initial  slopes  into  the  initial  hollows.  Every  stream  proceeds, 
by  degrading  and  aggrading  its  course,  to  develop  a  line  of  slope 
on  which  its  ability  to  do  work  shall  everywhere  equal  the  work 
that  it  has  to  do.  As  the  eminences  are  worn  down  and  the  hol- 
lows are  filled  up,  local  systems  that  were  at  first  independent 


704 


PHYSIOGRAPHIC  ESSAYS 


become  confluent,  and  the  drainage  of  the  higher  ones  is  dis- 
charged to  the  lower  ones.  Every  change  of  this  kind  will  call 
for  rearrangement  of  the  degraded  and  aggraded  slopes  in  the 
confluent  basins.  Ultimately,  all  the  separate  systems  will,  in 
one  combination  or  another,  find  /outlet  to  the  sea,  and  the 
waste  will  be  carried  a  long  distance  from  the  main  divides  to 
the  main  river  deltas. 

It  is  much  the  same  with  the  Action  of  the  sea.    Leaving  the 
on-and-off-shore  action  out  of  consideration  for  the  moment,  let 

us  view  only  the  long- 
shore action,  as  deter- 
mined by  the  dominant 
rather  than  by  the  pre- 
vailing movements  of 
the  littoral  waters. 
The  projections,  or 
headlands,  of  the  con- 
structional shore-line 
act  as  so  many  divides, 
on  either  side  of  which 
the  longshore  currents 
flow  away  from  the 
apex,  as  in  the  upper- 
most outline  in  Fig. 
109.  The  reentrants, 
or  bays,  are  so  many 
basins  into  which  the 


FIG.  109 


longshore  currents  converge  from  the  adjacent  headlands.  The 
headlands  are  slowly  worn  back,  and  the  waste  is  carried  along 
their  sides  into  the  bays,  where  it  forms  aggrading  pocket 
beaches  or  bridging  bars,  as  in  the  second  and  later  outlines 
of  Fig.  109.  The  initial  irregularity  of  shore  outline  is  thus  re- 
placed by  a  graded  outline,  grade  being  first  attained  in  the  bays, 
and  last  on  the  headlands,  much  as  was  the  case  with  stream 
action.  As  the  headlands  are  cut  farther  back  and  beaches  are 
formed  at  the  base  of  their  cliffs,  then  the  longshore  action 
is  more  and  more  thrown  into  one  direction  or  the  other  from 
the  ch/ef  headlands,  transportation  is  carried  on  past  many  of 


THE  OUTLINE  OF  CAPE  COD  705 

the  subordinate  headlands,  and  much  of  the  waste  finds  its  way 
into  the  chief  reentrants  of  the  shore-line,  as  in  the  lowermost 
outline  of  Fig.  109.  We  should  expect  to  find  inside  the  long- 
sweeping  curve  of  the  aggrading  shore-line  of  the  chief  bays 
more  or  less  distinct  record  of  the  sharp-curved  pocket  beaches 
of  an  earlier  stage. 

However  irregular  the  initial  shore-line  was  originally,  and 
however  many  divisions  were  then  made  in  the  direction  of  the 
longshore  currents,  the  time  will  come  when  only  a  few  of  the 
most  prominent  and  resistant  headlands  survive,  as  in  the  later 
outlines  of  Fig.  109  ;  elsewhere  the  longshore  action  is  developed 
into  a  continuous  movement.  Truly,  the  direction  of  transporta- 
tion along  the  graded  shore-line  is  sometimes  one  way,  sometimes 
the  other,  according  to  the  sweep  of  storm  winds ;  but  if  the 
dominant  currents  alone  are  considered,  the  movement  is  essen- 
tially constant.  The  graded  condition,  first  reached  on  the  pocket 
beaches,  comes  to  prevail  all  along  the  shore ;  ability  to  do  the 
work  of  transportation  is  everywhere  equal  to  the  work  of  trans- 
portation to  be  done. 

In  the  river  problem  the  number  of  independent  river  systems 
that  occupy  the  originally  deformed  surface  varies  with  the 
strength  of  the  initial  relief  and  with  the  rainfall.  A  light  rain- 
fall and  a  strong,  rapid-growing  initial  relief  of  resistant  rocks 
produce  many  independent  river  systems,  and  a  long  time  must 
elapse  before  a  general  grade  is  attained.  The  early  stage  of  this 
condition  is  illustrated  in  the  lava-block  mountains  of  southern 
Oregon,  so  well  described  by  Russell  (435).  But  a  heavy  rainfall 
and  a  faint,  slow-growing  initial  relief  of  weak  materials  may 
allow  the  immediate  development  of  a  single  river  system,  soon 
attaining  grade  over  the  whole  area  concerned.  So  with  the 
sea.  Moderate  longshore  action  and  strong  initial  irregularity 
of  resistant  rocks  break  up  the  longshore  currents  into  many 
systems  at  first ;  the  grading  of  the  shore-line  and  the  union  of 
the  many  currents  can  be  accomplished  only  after  a  long  time 
of  endeavor.  But  strong  longshore  action  and  moderate  initial 
irregularity  of  weak  materials  may  permit  continuous  longshore 
movements  for  a  long  distance  on  well-graded  beaches  almost 
from  the  very  first. 


706  PHYSIOGRAPHIC  ESSAYS 

Both  in  valleys  and  on  coasts  —  in  rivers  and  on  shores  — 
the  graded  condition  will  be  reached  sooner  on  certain  stretches 
than  on  others  ;  and  just  as  an  alternation  of  rough  rapids  and 
smooth-flowing  reaches  indicates  a  youthful  stage  of  river  life, 
so  an  alternation  of  ragged  headlands  and  smooth-beached  bars 
indicates  a  youthful  stage  of  shore-line  development.  But  in  time 
even  the  more  resistant  parts  Will  be  trimmed  off  so  as  to  ac- 
cord with  the  less  resistant,  and  'then  downstream  transportation 
—  or  longshore  movement  —  isj  well  developed  ;  the  adolescent 
stage  is  reached.  From  this  time  forward,  on  a  shore  as  in  a 
river,  the  grade  is  normally  changed  only  where  and  when  a 
change  of  load  calls  for  readjustment  ;  the  readjustment  necessi- 
tating an  aggradation  or  degradation  of  the  valley  floor,  or  an 
advance  or  retreat  of  the  shore-line,  as  the  load  may  increase 
or  decrease. 

It  should  of  course  be  understood  that  comparisons  of  this 
kind  are  not  formal  comparisons  in  which  the  condition  of  one 
member  may  be  inferred  immediately  from  those  of  its  analogue. 
The  purpose  of  the  comparison  is  not  to  compel  explanation,  but 
chiefly  to  borrow  illustration  of  the  systematic  processes  of  land 
sculpture  from  the  better  known  examples  of  river  action,  and 
apply  them  to  the  less  studied  examples  of  shore  action  ;  less 
studied  certainly  in  this  country,  where  our  great  interior  areas 
have  for  some  decades  past  absorbed  the  attention  of  geologists  ; 
more  studied  than  river  action  in  Great  Britain,  but  not  from 
the  point  of  view  here  taken. 

Under  favorable  conditions  irregular  shore-lines  may  be  smoothly 
graded  early  in  their  cycle  of  development.  This  is  well  illustrated 
in  the  case  of  Marthas  Vineyard.  Here  an  extremely  irregular 
constructional  shore  has  been  reduced  to  a  remarkably  even  and 
well-graded  outline  in  a  relatively  early  stage  of  the  attack  of  the 
sea  on  the  land ;  for  although  a  matter  of  two  or  three  miles  of 
the  southern  headlands  of  the  island  have  probably  been  cut  away 
by  the  sea  (Shaler,  349),  a  good  part  of  the  original  shore-line  still 
remains  in  the  branching  bays  behind  the  bridging  bars.  The 
straight-cliffed  headlands  stand  perfectly  in  line  with  the  bars 
across  the  bays.  The  later  stages  of  outline  on  graded  shores 
are  considered  in  the  third  section  below. 


THE  OUTLINE  OF  CAPE  COD  707 

APPLICATION  OF  THE  FOREGOING  TO  CAPE  COD 

The  foregoing  account  of  the  development  of  shore-lines  is 
perhaps  an  overlong  preparation  for  the  application  of  the  simple 
principles  that  govern  shore  changes  to  the  case  of  Cape  Cod ; 
but  the  excuse  for  the  details  into  which  I  have  entered  is  the 
desire  to  show  good  ground  for  the  conclusion  which  they  sup- 
port ;  namely,  that  on  a  coast  as  weak  as  the  mainland  of  Cape 
Cod,  any  originally  irregular  shore-line  would  soon  be  reduced  to 
grade  by  the  action  of  a  sea  so  energetic  as  the  Atlantic,  with 
its  frequent  southeast  and  northeast  storms.  Only  a  moderate 
time  and  a  moderate  recession  is  therefore  necessary  for  the  pro- 
duction of  the  even  northeast  cliff  of  High  head.  It  does  not, 
however,  follow  from  this  that  only  a  short  time  actually  elapsed 
in  this  work,  for  as  far  as  has  yet  been  stated,  the  High  head 
cliff  that  we  see  may  have  been  cut  far  back  from  the  first  posi- 
tion of  an  even  cliff  on  this  part  of  the  coast  line.  Whether  the 
time  was  long  or  short  can  be  best  determined  by  examining 
into  the  conditions  which  determine  the  development  of  the  bar 
by  which  the  cliff  is  now  protected,  this  being  the  second  prob- 
lem announced  above. 

It  should  be  noted  that  when  the  northeast  cliff  of  High  head 
formed  the  open  shore-line  of  this  part  of  the  Cape,  the  out- 
line must  have  extended  in  a  sympathetic  curve,  HBF^A,  for 
some  distance  southeast  of  its  present  limit ;  and  from  this  early 
form  there  must  have  been  a  gradual  change  to  the  shore-line  of 
to-day.  At  some  time  during  this  change  the  protecting  bar,  £f, 
must  have  been  built  out  to  the  northwest.  The  problem  is  to 
determine  at  what  stage  in  the  history  of  a  cliffed  shore-line 
such  a  bar  or  spit  might  grow  out  from  one  part  of  its  face  and 
protect  another  part. 

OFF-SHORE  BARS 

In  order  to  avoid  misapprehension,  it  is  advisable  to  make 
careful  distinction  between  those  bars  or  spits  which  spring  as 
tangent  attachments  to  a  cliffed  shore,  often  extending  into  com- 
paratively deep  water,  and  those  off-shore  bars  which  are  built 
up  from  the  bottom  in  shallow  water,  not  immediately  connected 


708 


PHYSIOGRAPHIC  ESSAYS 


with  the  mainland.  Examples  of  the  latter  class  are  common 
along  a  great  extent  of  our  southern  coast,  especially  where  the 
tides  are  weak.  Briefly  stated,  their  history  seems  to  be  as  fol- 
lows :  When  waves  roll  in  upon  a  shelving  shore,  as  in  Fig.  1 10, 
much  of  their  energy  is  expended  on  the  bottom.  Between  the 
line  of  their  first  action  far  off /shore  and  their  final  exhaustion 
on  the  coast,  C,  there  must  be  somewhere  a  zone  of  maximum 
action.  This  zone  must  lie  farther  seaward  when  large  storm 
waves  roll  in  than  when  the  sea  is  slightly  ruffled  in  fair  weather. 

Mainland 

**^__          C        M      L    M     J? 

~7r 


FIG.  no  « 

Let  the  zone  of  maximum  action  for  storm  waves  be  shown  by  Z 
in  profile.  Here  the  bottom  is  deepened ;  the  coarser  particles 
are  moved  landward,  forming  a  shoal  and  in  time  a  bar,  B\  inclos- 
ing a  lagoon,  Z ;  while  the  finer  particles  are  moved  seaward, 
beyond  the  limits  of  Fig.  109,  where  they  are  distributed  in  mod- 
erate thickness  over  a  considerable  area.  During  this  process 
we  may  imagine  the  storm  waves  to  say:  "We  cannot  to  advan- 
tage attack  a  coast  where  the  off-shore  water  shoals  so  gradu- 
ally ;  let  us  therefore  first  deepen  the  off-shore  bottom,  so  that 
we  may  afterwards  make  better  attack  on  the  coast."  So  saying, 
a  preliminary  off-shore  bar  is  built  up  by  the  storm  waves  in 


THE  OUTLINE  OF  CAPE  COD  709 

position  B1  \  and  afterwards,  at  times  of  exceptional  storms,  suc- 
cessive additions  may  be  made  on  its  outer  side,  as  _B" .  Wind 
action  builds  the  bar  up  with  dunes,  and  carries  much  sand  over 
into  the  lagoon.  But  a  time  will  come  when  the  bottom  farther 
to  seaward  has  been  deepened  enough  to  enable  even  the  greatest 
waves  to  act  severely  on  the  outer  slope  of  the  bar,  taking  from 
it  more  than  they  bring  to  it ;  then  the  outward  advance  of  the 
bar  is  changed  to  a  landward  retreat,  and  it  is  pushed  back  to 
such  a  position  as  B1".  This  change  in  behavior  may  be  taken  to 
separate  the  stages  of  youth  and  adolescence  in  the  development 
of  a  shore-line  of  this  kind. 

Young  bars  that  are  advancing  or  that  have  advanced  seaward 
may  often  be  recognized  by  belts  of  dunes,  B't  H1 ',  roughly  parallel 
to  the  shore,  inclosing  lines  of  marsh,  or  "  slashes"  (S),  as  they 
are  called  on  the  coast  of  New  Jersey.  Adolescent  bars,  retreating 
landward  like  Bin,  may  be  distinguished  by  the  exposure  of  the 
dark  mud  of  the  lagoon  marsh ,  M,  on  their  outer  slope,  as  is  suffi- 
ciently explained  by  the  diagrams.  Many  examples  of  this  kind 
might  be  cited.  In  time  the  retreat  of  the  bar  will  carry  it  back 
to  the  mainland ;  then,  as  long  as  the  marginal  cliff  is  not  too 
high,  the  "  dunes,"  D"",  will  be  heaped  directly  on  the  land  slope, 
and  the  mature  stage  of  shore  development  is  reached.  In  this 
stage  the  depth  of  water  near  the  shore  is  much  greater  than  it 
was  originally ;  degradation  of  the  sea  floor  reaching  to  depths 
much  below  low  tide. 

An  interesting  variation  on  this  type  of  coastal  forms  is  found 
on  coasts  whose  submarine  slope  varies,  so  that  off-shore  bars  are 
formed  in  one  district,  but  an  immediate  attack  is  made  on  the 
land  in  a  neighboring  district.  The  coast  of  New  Jersey  gives  a 
standard  example  of  this  kind.  About  Atlantic  City  the  bars  are 
built  off  shore  ;  about  Long  Branch  the  land  is  cut  back  in  a 
retreating  cliff  of  moderate  height.  Although  now  generally  re- 
treating and  exposing  marsh  mud  on  their  ocean  side  (Geol. 
Surv.  New* Jersey,  Ann.  Rep.  (1885),  80  et  seq.),  the  bars  fre- 
quently possess  dune  ridges  and  slashes,  as  if  they  had  once  ad- 
vanced seaward.  Somewhere  in  the  earlier  history  of  this  coast 
there  must  have  been  a  point  or  fulcrum  of  no  advance,  or  retreat 
between  the  advancing  bars  and  the  retreating  cliff.  It  should 


710  PHYSIOGRAPHIC  ESSAYS 

not  be  overlooked  that  longshore  action  has  a  share,  often  a 
large  share,  in  the  development  or  compound  forms  of  this  kind ; 
but  it  is  quite  conceivable  that  they  might  be  developed  essen- 
tially under  the  control  of  on-and-off -shore  action  alone.  A  second 
example  of  this  kind  is  perhaps  yco  be  found  in  the  combination 
of  the  bars  from  Chatham  to  Wauset  with  the  cliff ed  margin  of 
the  Cape  mainland  farther  no/th  ;  but  into  this  problem  it  is  not 
desirable  to  enter  further/at  present.  The  origin  of  tangent 
bars  or  spits,  built  out  into  comparatively  deep  water,  may  now 
be  taken  up. 

TANGENT  BARS  OR  SPITS 

In  order  to  understand  more  clearly  the  conditions  under  which 
tangent  bars  would  form,  it  is  necessary  to  return  for  a  few  mo- 
ments to  the  problem  of  the  varying  outline  of  a  graded  shore  as 
dependent  on  an  increase  of  load.  It  is  advisable  to  enter  this 
phase  of  the  problem  through  comparison  again  with  the  devel- 
opment of  rivers  and  valleys. 

In  the  case  of  adolescent  rivers,  the  increasing  dissection  of  the 
drainage  basin  by  growing  headwater  branches  may  frequently 
cause  the  load  to  continue  to  increase  after  the  first  attainment 
of  a  graded  slope  along  the  trunk  river.  As  a  consequence,  the 
trunk  river  must  aggrade  the  valley  floor,  forming  a  flood  plain, 
until  the  load  begins  to  decrease  later  on  in  maturity.  Much  in 
the  same  way  longshore  action  of  the  sea  on  a  coast  of  graded 
outline  may  gather  an  increasing  load  as  the  cliffs  retread  and 
become  longer  and  higher ;  and  with  this  increase  of  load,  certain 
parts  of  an  early-graded  outline  may  have  to  be  built  forward  into 
the  sea.  But  on  pursuing  this  comparison  a  step  further  we  find 
here,  as  in  some  earlier  cases,  a  contrast  replacing  the  agreement 
thus  far  traced  between  the  river  and  the  longshore  action.  Not 
only  the  load,  but  also  the  volume  of  a  river  increases  from  youth 
to  maturity  by  reason  of  the  better  development  of  stream  lines 
all  over  the  drainage  basin  ;  and  this  increase  of  volume  tends  to 
prevent  the  aggradation  asked  for  by  the  increase  of  load.  Simi- 
larly, the  volume  of  water  involved  in  the  longshore  movements 
becomes  greater  as  the  inequalities  of  a  young  shore-line  are 
reduced  to  the  smooth  curves  of  adolescence  and  maturity ;  but 


THE  OUTLINE  OF  CAPE  COD 


711 


here  the  increase  of  volume  causes  the  shore  waters  to  move  in 
curves  of  larger  radius  than  before,  and  this  change  may  require 
the  beaches  to  grow  forward  on  certain  concave  or  incurved  parts 
of  the  shore-line.  In  such  case  increase  in  the  volume  of  long- 
shore water  movements  may  cooperate  with  the  increase  of  load 
in  tending  to  build  the  land  out  into  the  sea.  Here  rivers  and 
longshore  currents  have  unlike  behavior. 

One  of  the  best  examples  of  this  kind  that  has  come  to  my 
notice  is  found  on  the  coast  of  Georgia  and  Florida,  where  the 
better  adjustment  of  coastal  bars  to 
shore  currents  and  the  consequent  in- 
crease in  volume  and  strength  of  the 
latter  seems  to  have  led  to  the  out- 
building of  the  several  'bars  that  are 
involved  in  the  southward  migration  of 
cape  Canaveral.  The  accompanying  dia- 
gram (Fig.  in)  illustrates  the  essential 
features  of  the  changes  here  inferred. 
The  general  attack  that  is  at  first  made 
nearly  all  along  the  ragged  coast  soon 
comes  to  be  resolved  into  two  diverse 
actions :  a  persistent  attack  on  the  chief 
medial  headlands,  while  the  subordinate 
headlands  are  protected  by  the  growth 
of  off-shore  bars.  Let  the  ragged  out- 
line of  Fig.  1 1 1  represent  the  original 
shore-line  of  an  uncompacted  land  mass. 
The  general  attack  by  the  sea  first  cuts 
off  all  the  headlands,  forming  cliffs  2,  3,  more  or  less  connected 
by  bars.  When  longer  and  higher  cliffs,  4,  are  developed,  they 
supply  so  large  an  amount  of  waste  and  allow  the  movement  of 
so  large  a  volume  of  water  along  shore  that  the  less  exposed 
cliff  of  earlier  intention  in  the  upper  part  of  the  figure  is  no 
longer  attacked,  but  is  protected  by  a  spit,  4',  that  springs  out 
from  the  main  cliff,  prolonging  its  curve  in  one  direction  or  the 
other,  —  here,  upward,  —  according  as  the  tides  and  the  on-shore 
winds  determine  the  direction  of  the  longshore  movement.  In 
this  case  on-and-off -shore  action  and  depth  of  water  have  little  to 


FIG.  in 


712  PHYSIOGRAPHIC  ESSAYS 

say.  Wherever  the  dominant  longshore  movement  advances,  there 
the  tangent  bar  must  grow,  whether  the  water  is  shallow  or  deep. 

ILLUSTRATION  FROM/THE  COAST  OF  NEW  JERSEY 

An  example  suitable  for/ illustration  of  this  case  is  found  in  the 
relation  of  Sandy  Hook /to  the  Long  Branch  cliffs  on  the  New 
Jersey  coast,  as  exhibit^  on  the  excellent  topographical  maps  of 
that  state.  Although  now  protected  by  the  spit  of  Sandy  Hook, 
both  Rumsor  neck  and  the  highlands  of  Navesink  are  truncated 
by  sea  cliffs.  The  truncation  must  have  been  accomplished  before 
the  spit  was  built,  and  therefore  before  the  Long  Branch  cliff  had 
been  pushed  back  to  its  present  position.  Stage  3  (Fig.  1 1 1)  essen- 
tially represents  this  relation.  In  the  change  from  earlier  stages 
to  the  present,  the  longshore  action  has  increased  in  consequence 
of  the  general  smoothing  of  the  outline,  and  the  direction  of  long- 
shore movement  has  been  somewhat  changed,  so  that  now  instead 
of  carrying  the  waste  from  the  Long  Branch  cliff  directly  to  the 
truncated  headlands  next  north,  it  is  carried  along  an  independent 
path  forming  the  spit  of  Sandy  Hook  outside  of  the  line  of  trun- 
cation. It  is  interesting  to  notice  that  the  Long  Branch  cliffs 
were  evenly  graded,  and  that  the  spit  was  formed  rather  early  in 
the  general  attack  of  the  sea  on  the  land  hereabouts,  and  that  a 
very  slight  change  in  the  outline  of  the  chief  cliff  sufficed  to  cause 
the  growth  of  the  spit  outside  of  the  subordinate  cliffs  farther  north. 
The  various  fluctuations  in  the  growth  of  the  spit  and  the  inter- 
mittent destruction  of  its  slender  bar  are  described  on  page  78  of 
the  annual  report  of  the  New  Jersey  Geological  Survey  for  1885. 

The  Long  Branch  cliff  has  for  some  time  been  retreating  under 
the  blows  of  the  Atlantic  breakers.  The  farther  it  retreats  the 
longer  the  stretch  of  cliff  becomes  ;  it  is  undoubtedly  much 
longer  now  than  formerly.  It  may  be  fairly  inferred  that  the 
two  great  spits,  to  the  south  as  well  as  to  the  north  of  the  cliff, 
have  always  been,  as  now,  essentially 'tangent  to  the  cliff  front. 
It  follows  necessarily  that  the  point  of  the  attachment  of  the 
spits  to  the  mainland  has  shifted,  and  that  the  spits  have  also 
been  pushed  backward  at  equal  pace  with  the  retreat  of  the  cliff. 
With  these  conclusions  in  mind,  the  problem  of  High  head  and 
the  northeast  bar  may  at  last  be  taken  up. 


THE  OUTLINE  OF  CAPE  COD  713 

GROWTH  OF  THE  PROVINCELANDS 

There  is  good  reason  to  think  that  the  analogy  between  Sandy 
Hook  and  the  Provincelands  pointed  out  by  Admiral  Davis  may 
be  carried  much  further  than  he  suspected.  The  great  convex 
cliff  line  on  the  back  of  the  Cape  corresponds  to  the  slightly  con- 
vex line  of  the  Long  Branch  cliff ;  the  northeast  cliff  of  High 
head  is  the  counterpart  of  the  protected  cliff  of  the  Navesink 
highlands ;  the  slender  bar  that  springs  tangent  to  the  curve  of 
the  back  of  the  Cape  and  runs  to  the  broad  peninsula  of  the  Prov- 
incelands is  essentially  a  repetition  of  the  slender  bar  that  springs 
north  from  the  Long  Branch  cliff  and  runs  to  the  broadened 
peninsula  of  Sandy  Hook.  The  point  where  the  bar  now  springs 
northwestward  from  the  long  convex  back  of  the  Cape  is  not  the 
point  where  the  bar  first  began  to  grow.  Its  original  point  of 
attachment  must  have  been  southeast  of  the  present  point ;  and 
in  the  change  from  the  original  to  the  present  arrangement,  both 
the  cliff  and  the  slender  bar  must  have  been  forced  back,  in  the 
very  manner  already  described  for  the  example  in  New  Jersey. 
Marindin's  report  gives  precise  data  for  the  retreat  of  the  cliff ; 
and  the  story  of  the  buried  canoe,  recorded  by  Thoreau,  gives 
support  to  the  retreat  of  the  bar  near  its  point  of  attachment. 
In  both  examples  the  further  part  of  the  great  spit  has  grown  by 
addition  to  its  seaward  side  in  order  to  keep  the  outline  in  a  curve 
sympathetic  with  the  retreating  cliff ;  the  outward  or  eastward 
growth  of  Sandy  Hook  being  described  on  page  77  of  the  annual 
report  of  the  New  Jersey  Geological  Survey  for  1885  ;  the  similar 
growth  of  the  Provincelands  is  more  fully  stated  below.  As  a 
result  of  the  outward  growth  of  the  spit  while  the  cliff  is  retreat- 
ing, there  must  be  a  neutral  point  or  fulcrum  of  no  change  some- 
where on  the  connecting  bar ;  and  with  the  further  straightening 
of  the  cliff  front,  the  position  of  this  fulcrum  must  generally  shift 
toward  the  spit,  as  shown  by  F±,  F%,  F%  (Fig.  n  i). 

The  original  point  of  attachment  of  the  connecting  bar  on  Cape 
Cod  must  have  been  at  the  intersection  of  two  converging  lines 
determined  by  the  northeast  cliff  of  High  head  and  the  innermost 
or  oldest  of  the  bars  in  the  Provinceland  peninsula.  The  first  of 
these  lines  is  well  defined,  HB  (Fig.  112);  the  second  is  less 


7H 


PHYSIOGRAPHIC  ESSAYS 


distinct,  but  appears  to  be  recorded  in  a  sand  bar  on  the  line 
The  form  of  this  bar  has  probably  been  somewhat  changed  by 
wind  action,  yet  the  trend  of  its  inner  margin  along  the  shore  of 
East  harbor  is  comparatively  ^traight,  as  if  it  had  not  been  much 
altered  from  the  form  given /when  it  was  built.  Its  trend  departs 
slightly  from  the  direction/of  the  adjacent  Atlantic  shore,  as  if  it 
had  been  determined  by  Conditions  now  vanished. 

The  intersection  of  the  two  guide  lines  HB  and  EF^  when  pro- 
longed to  the  east-southeast,  is  found  at  a  point  flt  about  four 


TLANTIC 
OCEAN 


FIG.  112 

thousand  feet  off  the  present  shore,  and  about  a  mile  and  two 
thirds  east-southeast  from  the-  present  point  of  attachment  of 
the  springing  bar.  Judging  by  the  present  rate  of  retreat  of 
the  cliff  line,  this  outer  position  must  have  been  occupied  about 
twelve  hundred  years  ago.  These  figures  are  of  necessity  only 
approximate,  but  they  are  believed  to  give  a  fair  indication  of 
the  order  of  magnitudes  involved,  both  in  space  and  time.  We 
may  then  infer  that  when  the  general  outline  of  the  back  of  the 
Cape  had  assumed  the  position  of  the  line  AF^BH,  the  shore 
was  well  enough  graded  to  supply  material  for  the  building  of  a 


THE  OUTLINE  OF  CAPE  COD  715 

spit ;  and  that  the  curvature  of  the  shore  at  the  point  Fv  assigned 
for  the  beginning  of  the  spit,  was  such  that  the  dominant  long- 
shore currents,  moving  from  south  to  north  in  flood  tide  or 
under  southeast  storms,  could  no  longer  follow  the  shore,  but 
departed  from  it  outwardly  by  a  small  angle.  Thus  the  pro- 
tecting bar  F^E  began  to  grow  in  front  of  the  High  head  cliff. 

At  an  earlier  stage  the  longshore  currents  must  have  been 
much  interrupted  by  the  irregularities  of  the  original  shore-line. 
No  large  and  well-developed  current  could  at  that  time  follow 
these  irregularities.  But  as  the  headlands  were  cut  back  and  the 
bays  bridged  across,  and  the  shore  assumed  the  outline  ABH, 
then  the  resistance  to  the  development  of  the  current  became 
less  and  less  ;  thereby  the  current  became  stronger  and  stronger, 
and  desired  a  straighter  and  straighter  path  for  its  movement. 
At  the  same  time,  a  greater  and  greater  volume  of  waste  was 
supplied  from  the  growing  cliffs.  As  long  as  the  back  of  the 
Cape  projected  farther  into  the  sea  than  now,  the  northward 
shore  current  may  have  swung  pretty  well  around  the  mainland, 
as  sketched  in  line  ABH.  But  as  the  east  side  of  the  Cape  was  cut 
away  and  straightened,  and  as  the  shore  current  grew  stronger 
and  stronger,  it  became  increasingly  difficult  for  the  waters  to 
turn  the  curve  that  led  to  High  head ;  and  at  last,  when  the  turn- 
ing was  impossible,  the  spit  began  to  form  on  the  line  J\E.  As 
the  change  progresses  the  current  swings  on  a  fulcrum,  F2 ;  the 
spit  broadens  by  the  external  addition  of  new  bars,  F2G,  as  well 
as  by  the  formation  of  sand  dunes  inside  of  the  curve  ;  and  the 
fulcrum  shifts  along  the  shore  to  the  northwest,  as  indicated 
by  the  points  F2,  Fs  (Fig.  1 1 2),  in  the  manner  already  explained 
for  Fig.  in. 

The  important  point  to  note  is  that  here,  just  as  on  the  New 
Jersey  coast,  the  grading  of  the  initial  irregular  shore-line  into  a 
curved  cliff  shore,  and  the  straightening  of  the  curved  cliff  shore 
enough  to  require  the  growth  of  the  tangent  bar,  must  have  been 
accomplished  early  in  the  development  of  so  weak  a  land  mass  as 
Cape  Cod  in  face  of  waves  so  strong  as  those  of  the  Atlantic. 


;i6  PHYSIOGRAPHIC  ESSAYS 

DIMENSIONS  OF  THE  ORIGINAL  CAPE 

Now  inasmuch  as  no  very  long  time  can  have  been  required 
for  the  Atlantic  waves  to  wear  back  the  original  shore-line  of  the 
Cape  to  a  graded  outimz/AItff,  of  which  the  High  head  cliff  is  a 
part,  and  inasmuch  as  tie  growth  of  the  springing  spit  must  have 
been  begun  soon  after  the  grading  of  the  shore,  it  follows  that 
the  original  constructional  outline  of  the  land  in  front  of  the  High 
head  cliff  cannot  ^iave  extended  far  into  the  sea.  I  have  given  it 
an  extension  of  three  thousand  feet  in  Fig.  107.  A  similar  original 
extension  of  all  the  mainland  of  the  Cape  may  be  assumed  outside 
of  the  graded  shore-line,  ABHy  that  existed  before  the  springing 
spit  was  formed ;  and  thus  the  original  outline  of  the  eastern  side 
of  the  mainland  has  been  roughly  sketched  in.  As  drawn  in  Fig. 
107,  the  greatest  retreat  from  the  original  shore  to  the  present 
shore  is  nearly  two  and  a  half  miles,  and  at  the  present  strength 
of  wave  action,  three  thousand  or  four  thousand  years  may  be 
roughly  taken  to  have  sufficed  for  the  accomplishment  of  this 
change.  This  time  is  probably  too  long  rather  than  too  short,  for 
the  retreat  now  must  be  slower  than  when  the  cliff  was  lower. 

It  should  be  carefully  understood  that  the  period  here  com- 
puted does  not  measure  post-glacial  time  ;  for,  as  already  stated, 
it  is  believed  that  the  land  hereabouts  stood  somewhat  higher 
than  now  during  the  accumulation  of  the  stratified  sands,  and 
that  only  after  the  time  of  accumulation  were  the  valleys  and  low 
grounds  slightly  submerged  by  a  moderate  depression  of  the  land, 
and  the  work  whose  duration  is  here  computed  begun.  The  time 
that  passed  while  the  sea  was  at  work  on  some  lower  shore  is 
not  measured.  There  is  no  indication  of  a  recent  elevation  of  the 
land  hereabouts,  as  far  as  the  shore  features  testify ;  even  the 
protected  cliffs  of  High  head  are  cut  down  to  present  sea-level. 

The  Nauset  bar  extends  southward  from  the  cliff  at  the  point 
N.  The  earlier  positions  were  prolongations  of  the  lines  A,  D. 
The  point  of  attachment  must  therefore  have  migrated  to  the 
southwest ;  the  retreat  of  the  cliff  front  determining  the  retreat 
of  the  bar  that  stands  in.  line  with  it.  How  the  problematic 
islands  off  Chatham  affected  the  behavior  of  the  bar  is  not  here 
inquired  into. 


THE  OUTLINE  OF  CAPE  COD  717 

Inasmuch  as  the  recession  of  the  eastern  shore  is  believed  to 
have  been  of  moderate  measure,  the  loss  on  the  western  shore 
must  have  been  still  less.  This  is  considered  in  a  later  section. 


THE  ORIGIN  OF  RACE  POINT 

Two  important  consequences  follow  from  the  swinging  of  the 
shore  current  on  its  movable  fulcrum.  The  first  gives  explana- 
tion of  the  overlapping  of  the  newer  shore-lines  outside  of  the 
older  body  of  the  peninsula.  This  is  only  a  repetition  of  the  proc- 
ess by  which  the  spit  first  departed  from  the  beach  on  the  back 
of  the  Cape  itself.  The  outer  margin  of  the  Provinceland  penin- 
sula is  therefore  its  very  youngest  part,  and  not  its  oldest,  as 
supposed  by  Whiting.  The  long  bar,  F^JK,  ending  in  Race  point, 
is  a  distinct  external  addition  to  the  older  body  of  the  Province- 
lands,  and  a  long,  narrow  "slash"  is  included  behind  it.  It  has 
grown  out  into  comparatively  deep  water,  for  the  twenty-fathom 
line  lies  only  seventeen  hundred  feet  off  shore  to  the  northwest. 
Peaked  hill  bar  may  be,  as  the  commissioners  have  plausibly 
suggested,  the  embryo  of  still  another  external  bar. 

It  may  be  noted  that  small  spits  departing  tangentially  from 
curved  beaches  are  not  uncommon.  The  map  accompanying 
Whiting's  report  shows  two  of  them  near  Wood  end,  one  point- 
ing east,  the  other  north,  from  the  sharp  curve  of  the  bar,  as  if 
determined  by  a  strong  southwest  storm,  whose  waves  worked 
eastward  and  northward  from  the  apex  of  the  curve  at  Wood  end. 
A  minute  spit  of  this  kind  is  shown  on  the  chart  of  Cape  Cod  bay 
(Coast  chart  1 10,  printed  1890),  a  little  northeast  of  Race  point ; 
but  a  later  edition  of  the  chart  (1892)  carries  a  smooth  curve 
around  the  point.  Small  examples  of  these  forms,  trending  east- 
ward, were  seen  on  the  south  shore  near  Long  point  light,  at  the 
time  of  my  last  visit  to  the  Cape. 

THE  WASTING  SHORE  FROM  RACE  POINT  TO  WOOD  END 

The  second  consequence  of  the  outward  deflection  of  the  cur- 
rent around  the  peninsula  is  the  rapid  consumption  of  the  bar, 
>  that  extends  south  from  Race  point  inlet  to  Wood  end, 


718  PHYSIOGRAPHIC  ESSAYS 

the  long  "  finger  "  at  the  end  of  the  Cape.  This  suggests  a  pre- 
liminary digression.  Wonder  is  often  expressed  at  the  ability  of 
sand  bars  to  withstand  the  violence  of  the  surf  that  breaks 
unceasingly  upon  them.  The  sancfe\are  entirely  unconsolidated, 
and  their  surface  layers  are  moved  by  every  surge  of  the  waters. 
Yet  the  form  of  the  bar  changes  very  slowly.  The  reason  for 
this  must  be  found  in  the  continual  feeding,  from  the  cliffs  and 
from  the  bottom  off  shore,  by  which  the  volume  of  the  bars  is 
sustained.  The  bars  of  our  southern  Atlantic  coast  presumably 
receive  much  of  their  sand  from  the  bottom.  Sandy  Hook  receives 
much  of  its  supply  from  the  retreating  cliffs  at  Long  Branch.  If 
the  supply  be  withheld,  the  bar  will  be  rapidly  swept  away.  It 
may  not  be  that  the  grains  of  sand  are  actually  ground  to  dust, 
but  that  they  are  brushed  along,  and  when  no  followers  come  to 
take  their  place,  it  is  left  vacant,  and  the  face  of  the  bar  retreats  ; 
its  dunes  are  cut  back,  and  a  low  cliff  shore  is  formed. 

As  long  as  the  outside  of  the  peninsula  formed  a  continuous 
curve,  sand  was  carried  along  it  in  plenty  from  the  cliff  and  the 
sea  floor  on  the  back  of  the  Cape,  and  probably  also  from  the 
shoals  where  Webbs  island  and  its  vanished  mates  once  stood  off 
Chatham.  This  condition  is  represented  in  line  DGVW.  But  as 
the  cliff  from  Nauset  to  Highland  was  cut  farther  back,  and  the 
shore  current  became  unable  to  follow  its  earlier  path  along  the 
margin  of  the  peninsula,  the  additional  bar,  ending  in  Race  point, 
was  laid  out,  and  the  long,  marshy  "  slash  "  was  inclosed  behind 
it.  From  the  beginning  of  this  additional  bar  until  the  present 
time,  the  supply  of  sand  carried  around  the  western  curve  of  the 
peninsula  was  greatly  reduced  ;  at  times  it  may  have  ceased  en- 
tirely. The  supply  being  thus  reduced  or  cut  off,  the  bar  south- 
ward from  Race  point  inlet  nearly  to  Wood  end  rapidly  wasted ; 
and  the  sand  taken  from  it  by  northwest  gales  went  to  supply 
the  correspondingly  rapid  growth  of  Long  point,  WX,  into  Prov- 
incetown  harbor,  which  Whiting  shows  to  have  extended  many 
feet  eastward  in  the  fifty  years  past.  Like  Race  point,  Long 
point  has  advanced  into  comparatively  deep  water ;  the  twenty- 
fathom  curve  lies  only  six  hundred  feet  off  shore  :  the  same 
depth  is  not  found  for  almost  three  miles  off  the  cliffed  shore 
of  the  back  of  the  Cape. 


THE  OUTLINE  OF  CAPE  COD  719 

THE  WESTERN  SIDE  OF  THE  CAPE 

The  western  side  of  the  Cape  offers  simpler  problems  than 
those  of  the  eastern  side.  The  first  task  here  attempted  by  the 
waves  was  the  development  of  the  long  west  straight  shore-line, 
HQTC,  of  which  only  the  extremities  now  remain.  This  does  not 
seem  to  have  required  anywhere  a  greater  recession  than  three 
thousand  feet.  It  must  have  been  accomplished  chiefly  by  north- 
west gales  and  north-to-south  shore  currents,  by  which  the  waste 
gathered  from  the  more  continuously  cliffed  shore  was  carried 
southward  to  tie  together  the  several  islands  below  South  Truro. 
If  southwest  gales  and  south-to-north  shore  currents  had  been 
dominant,  an  acuminate  spit  should  have  been  formed  in  prolonga- 
tion of  High  head,  where  the  waste  would  have  been  supplied 
from  both  sides  of  the  Cape ;  but  of  this  there  is  no  sign. 

The  modification  of  the  west  straight  shore-line  by  the  excava- 
tion of  the  present  concave  shore-line,  QPT,  undoubtedly  results, 
as  has  already  been  stated,  from  the  disturbance  of  antecedent 
conditions  that  was  caused  by  the  growth  of  the  Provincelands 
to  the  northwest.  The  northwest  gales  gradually  came  to  have 
less  and  less  influence  ;  for  some  time  past  they  must  have  ceased 
to  be  dominant ;  the  chief  control  of  shore  movements  now  seems 
to  be  in  the  hand  of  the  weaker  southwest  gales  ;  for  both  the 
offsetting  spit  at  the  mouth  of  Pamet  river,  P,  and  the  outspring- 
ing  bar,  QR,  that  protects  High  head  on  the  west  imply  a 
northward  transportation  of  sands.  Some  southward  movement, 
however,  still  occurs,  as  might  be  expected ;  for  at  the  faint  angle, 
T,  where  the  older  straight  shore-line,  HQTC,  is  now  cut  by  the 
concave  shore-line,  QPT,  a  spit  projecting  to  the  southwest  seems 
to  have  been  begun,  and  its  continuation  under  water  is  indicated 
by  a  shoal  of  sympathetic  curvature,  TU,  some  five  and  a  half 
miles  in  length.  How  far  this  shoal  may  be  a  new  feature,  origi- 
nating with  the  excavation  of  the  concave  shore-line,  or  how  far 
it  may  be  of  much  greater  age,  dependent  on  the  extensive 
Billingsgate  shoals,  where  outlying  islands  are  thought  to  have 
originally  stood,  is  for  the  present  an  undecided  question. 


c 


720  PHYSIOGRAPHIC  ESSAYS 

\ 
PROTECTION  OF  PROVINCETOWN  HARBOR 

A  matter  of  considerable  economic^  importance  turns  on  the 
changes  experienced  by  the  "wrist"  or  the  Cape,  the  narrowest 
part  of  the  bar  that  connects  the  mainland,  or  "forearm,"  of  the 
Cape  with  the  peninsula,  or  "  hand."  The  people  of  Provincetown 
feel  anxiety  lest  the  sea  should  breach  the  bar  and  wash  a  great 
amount  of  sand  westward  past  High  head  into  their  excellent 
harbor.  The  records  of  changes  in  the  bar  that  connects  Sandy 
Hook  with  the  Long  Branch  cliffs  give  ground  for  this  anxiety. 
The  point  that  I  wish  here  to  call  attention  to  is  that  the  only 
part  of  the  northeast  shore  that  is  liable  to  be  broken  through 
lies  on  the  stretch,  BF%,  between  the  point  where  the  connecting 
bar  springs  northwest  from  the  great  cliff  and  the  point  where 
the  "fulcrum"  is  at  present  located.  Within  this  stretch  the  bar 
is  generally  retreating,  being  cut  on  the  outer  side  and  recon- 
structed on  the  inner  side. 

Two  safeguards  may  be  suggested.  One  would  cause  the  ful- 
crum to  migrate  southeastward,  thus  diminishing  the  length  of 
the  narrow  and  breakable  bar,  and  at  the  same  time  increasing 
its  breadth  and  strength.  This  would  be  accomplished  by  the 
construction  of  bulkheads  along  the  outside  of  the  narrow  bar, 
or  "  wrist,"  so  as  to  catch  the  drifting  sand  instead  of  allowing  it 
to  pass  by;  thus  the  bar  might  be  broadened  and  strengthened. 
Judging  by  the  rapidity  with  which  the  body  of  a  wrecked  vessel 
causes  an  accumulation  of  sand  on  its  southeastern  side,  a  signifi- 
cant addition  to  the  narrow  bar  might  soon  be  made  in  this  man- 
ner. Manifestly,  the  greatest  economy  in  the  use  of  the  drifting 
sand  requires  that  the  bulkheads  should  be  continually  built  out 
so  as  always  to  project  a  little  beyond  the  aggrading  shore-line. 
There  are  indications  that  this  very  result  is  at  present  being 
accomplished  by  natural  process,  for  the  beach  in  the  narrow 
stretch,  JBF&  is  now  notably  broadened  in  front  of  its  former  line 
at  the  base  of  the  surmounting  dunes. 

A  more  economical  and  enduring  protection  of  Provincetown 
harbor  than  the  above  plan  suggests  has  been  already  secured  by 
completing  the  extremity  of  the  bar,  QR,  that  some  years  ago 
almost  inclosed  East  harbor  ;  so  that  if  storm  waves  should 


THE  OUTLINE  OF  CAPE  COD 


721 


temporarily  breach  the  narrow  connecting  bar  on  the  ocean  side, 
—  the  "  wrist  "  of  the  "  hand  "  of  Provincetown  at  the  end  of  the 
"bended  arm  of  Massachusetts,"-  — all  the  sand  that  was  carried 
through  the  breach  would  settle  in  East  harbor,  and  thereby 
strengthen  the  embankment  against  further  encroachments.  A 
second  protecting  dike  has  been  built  across  the  marsh  northeast- 
ward from  near  High  head.  The  fear  that  in  case  the  narrow 
connecting  bar,  or  "wrist,"  should  be  breached,  the  whole  action 
of  the  Atlantic  longshore  currents  would  thereafter  be  directed 
through  the  breach  into  Provincetown  harbor,  is  groundless.  The 
whole  history  of  the  growth  of  the  peninsula  demonstrates  that 
the  longshore  currents  must  continue  to  swing  in  long  curves 
of  large  radius  in  the  future  as  in  the  past. 

The  danger  of  silting  up  the  Provincetown  harbor  by  drift 
coming  from  the  west  concave  shore-line  along  the  west  protect- 
ing bar  of  High  head  does  not  appear  to  be  imminent,'  for  the 
processes  of  transportation  are  comparatively  slow  on  the  inner 
side  of  the  Cape  ;  but  the  danger  is  nevertheless  real,  and  nothing 
but  an  extensive  and  expensive  system  of  bulkheads  from  North 
Truro  northward,  on  the  stretch  PQ,  appears  to  be  sufficient  to 
avert  it. 

The  destruction  of  the  narrow  strip  of  sand-bar  shore,  VW, 
between  Race  point  and  Wood  end  seems  to  me  to  threaten 
Provincetown  harbor  with  a  greater  danger  than  any  that  it  is 
exposed  to  from  the  east.  This  shore  is  now  wasting  rapidly. 
Once  broken  through,  the  currents  driven  by  northwest  gales, 
as  well  -as  by  the  rising  tide,  would  no  longer  have  to  swing 
around  Wood  end,  W,  and  deliver  their  load  of  drifting  sand  to 
Long  point,  X\  they  would  in  all  probability  invade  the  harbor 
directly,  cutting  away  the  low-tide  flats  that  now  expand  south  of 
the  village,  and  throwing  the  detritus  thus  gained  into  the  harbor. 
Attention  has  been  called  to  this  danger  by  Marindin  in  the  United 
States  Coast  Survey  Report  for  1891,  Appendix  8.  While  bulk- 
heads may  delay  the  destruction  of  the  narrow  bar,  they  can  hardly 
preserve  it  even  through  a  brief  historical  period.  It  has  been 
proposed  to  abandon  the  wasting  bar  to  its  fate,  and  to  protect 
the  harbor  by  building  a  dike  from  the  west  end  of  the  village 
across  the  flats  to  Wood  end.  A  partial  protection  might  be 


722  PHYSIOGRAPHIC  ESSAYS 

gained  by  building  bulkheads  on  the  northern  shore  of  the  penin- 
sula, two  or  three  miles  east  of  Rade  point,  K.  Drifting  sand 
from  the  east  would  then  be  stopped  there.  Race  point,  no 
longer  so  well  supplied  with  sand  as  now,  would  be  wasted  by 
the  northwest  storms,  and  the  sands  carried  from  it  would  go 
southward  to  repair  the  shore  towards  Wood  end.  The  protec- 
tion of  the  bar  northeast  of  High  head  near  Fz  would,  to  a  certain 
extent,  work  in  the  same  direction  by  diminishing  the  supply  of 
sand  for  the  Race  point  bar ;  but  a  considerable  time  might  elapse 
before  any  advantageous  effect  from  this  cause  would  be  felt. 

THE  FUTURE  OF  THE  CAPE 

The  encroachment  of  the  sea  on  the  back  of  the  Cape  is 
undoubtedly  destined  to  continue  until  the  Truro  mainland  is 
all  consumed  north  of  Orleans,  the  "elbow  "  of  the  bended  arm. 
At  the  present  rate  of  recession  —  3.2  feet  a  year  —  eight  or 
ten  thousand  years  will  be  required  for  this  task ;  and  this 
without  considering  the  aid  given  by  the  waves  of  Cape  Cod 
bay,  whose  concave  sweep  along  the  Truro  shore  shows  their 
competence  to  do  no  insignificant  share  of  the  work. 

It  does  not  seem  at  all  likely  that  while  the-*rest  of  the  Truro 
mainland  is  wearing  away,  the  spit  at  Race  point  will  of  itself 
curve  around  to  the  south,  and  thus  save  from  destruction  the 
narrowing  bar  which  incloses  Provincetown  harbor  on  the  west. 
A  great  volume  of  transported  sand  would  be  needed  to  continue 
the  bar  in  the  deep  water  through  which  its  present  curve  would 
lead.  Moreover,  the  shoal  known  as  Peaked  hill  bar  may,  as  has 
been  suggested,  mark  the  beginning  of  a  shore-line  exterior  to 
that  of  the  present  Race  point  curve.  It  is  possible  that  as  addi- 
tional tangent  spits  are  lapped  on  the  outside  of  the  curve,  Race 
point  will  be  cut  back  by  a  current  from  the  northwest,  working 
opposite  to  the  great  current  that  rounds  the  peninsula  from  the 
east ;  a  cuspate  or  acuminate  spit  being  then  formed  in  the  angle 
between  the  two,  such  as  now  exists  at  Great  point,  Nantucket. 
There  the  transportation  of  shore  waste  is  northward  on  the  east 
shore  and  southward  on  the  west  shore,  according  to  the  memoir 
by  Admiral  Davis  ;  this  being  proved  by  the  drift  of  coal  and 


THE  OUTLINE  OF  CAPE  COD  723 

bricks  from  vessels  wrecked  on  the  east  shore  (139).  The  occur- 
rence of  these  "cuspate  forelands,"  as  Gulliver  has  called  them, 
is  not  so  much  of  a  rarity  in  nature  as  might  be  imagined  from 
the  little  that  appears  about  them  in  books ;  their  growth  being 
sometimes  attributable  to  accordant  currents  that  flow  towards 
the  point  on  either  side ;  sometimes  to  opposing  currents,  one 
flowing  inwards,  the  other  outwards.  Good  reasons  have  been 
given  by  Abbe  for  believing  that  cape  Hatteras  and  the  other 
cuspate  capes  of  the  Carolina  coast  have  been  built  between 
opposing  currents  (489). 

The  Provincetown  peninsula  may  be  expected  to  outlast  the 
Truro  mainland  ;  for  as  long  as  the  latter  exists,  the  former  must 
receive  contributions  from  it.  But  when  the  mainland  is  washed 
away,  —  ten  thousand  years  hence,  at  the  present  rate  of  wear- 
ing, —  then  Provinceland  must  rapidly  disappear.  Sable  island, 
a  long  sand  bar  off  Nova  Scotia,  is  perhaps  to  be  regarded  as  the 
vanishing  remnant  of  a  destroyed  drift  island  [see  Trans.  Roy. 
Soc.  Canada,  XII  (1894),  Pt.  II,  3-48;  also,  note  in  Science, 
II  (1895),  886].  It  may  in  this  sense  be  taken  to  represent  a 
future  stage  in  the  destruction  of  Cape  Cod.  All  these  changes 
are  rapid,  as  changes  go  on  the  earth's  surface.  The  Truro  main- 
land will  soon  be  destroyed,  and  the  sands  of  Provinceland  will 
be  swept  away  as  the  oceanic  curtain  falls  on  this  little  one-act 
geographical  drama. 

REFERENCES 

Abbe,  C.    Proc.  Boston  Soc.  Nat.  Hist.,  XXVI  (1895). 

Chamberlin,  T.  C.    "  Terminal   Moraine  of  the   Second   Glacial  Epoch." 

U.S.  Geol.  Surv.,  Ill  Ann.  Rep.  (1883). 
Davis,  C.  H.    "Memoir  upon  the  Geological  Action  of  the  Tidal  and  Other 

Currents  of  the  Ocean."  Mem.  Am.  Acad.  (Boston,  1849),  ^ •>  J :  7-1 5^- 
Davis,  W.  M.    "  Facetted  Pebbles  on  Cape  Cod."    Proc.  Boston  Soc.  Nat. 

ffist.,XXVl  (1893),  166-175. 
Freeman,  F.    History  of  Cape  Cod.     1860. 
Girard,  J.     La  Geographic  Littorale.    Paris,  1895. 
Gulliver,  F.  P.    Bull.  Geol.  Soc.  Am.,  VII  (1896). 
Hitchcock,  E.    Geology  of  Massachusetts,  I.    1841. 
Marindin,  H.  L.    (a)  "Encroachment  of  the  Sea  upon  the  Coast  of  Cape 

Cod,  Massachusetts."   U.  S.  Coast  Surv.  Rep.  ( 1 889),  403-407 ;  chart  28. 
(£)  U.  S.  Coast  Surv.  Rep.  (1891),  Appendix  8,  with  chart. 


724 


PHYSIOGRAPHIC  ESSAYS 


Mitchell,  H.  (a)  "  Report  .  .  .  concerning  Nausett  Beach  and  the  Peninsula 

of  Monomoy."     U.  S.  Coast  Surv.  Rep.  (1871),  134-143- 
(£)  "  Additional  Report  on  the  Changes  in  the  Neighborhood  of  Chatham 
and  Monomoy."     Ibid.  (1873),  103-107. 

"  Report  of  the  Trustees  of  Public  Reservations  on  the  Subject  of  the  Prov- 
ince Lands."  Mass.  Legislature,  House,  Pub.  Doc.  339  (February, 
1893),  6. 

Russell,  I.  C.     U.S.Geol.  Surv.,  IV  Ann.  Rep.,  435. 

Shaler,  N.  S.  "  Geology  of  Marthas  Vineyard."  U.  S.  GeoL  Surv.,  VII  Ann. 
Rep.  (1888). 

Thoreau,  H.  D.  Narrative  of  his  Excursions  on  Cape  Cod  in  1849,  1850, 
1855.  See  "Cape  Cod,"  in  new  Riverside  edition  of  Thoreau's  Works, 
1894. 

Upham,  W.    (a)  Geology  of  New  Hampshire,  III,    300-305.    1878. 

(£)  "The  Formation  of  Cape  Cod."  Am.  Nat.  (1879),  489-502,  552-565. 

Weule,  K.  "  Beitrage  zur  Morphologic  der  Flachkiisten,"  Kettlefs  Zeitschr. 
wiss.  Geogr.,  VIII  (1891),  211-256. 

Whiting,  H.  L.  "  Report  on  the  Special  Study  of  Provincetown  Harbor, 
Massachusetts."  U.  S.  Coast  Surv.  Rep.  (1867),  149-1  $7- 


XXVI 
THE  MOUNTAIN   RANGES  OF  THE  GREAT   BASIN 

Historical  Statement.  The  larger  mountain  ranges  of  the  Great 
Basin  offer  problems  of  especial  interest,  inasmuch  as  the  faulting 
by  which  their  present  relief  is  believed  to  have  been  produced 
is  not  proved  by  stratigraphic  evidence  of  the  kind  familiar  to 
geologists,  but  by  physiographic  evidence  of  a  kind  to  which  little 
attention  is  usually  given.  These  ranges  were  described  by  King 
in  1870  as  "  ordinarily  the  tops  of  folds  whose  deep  synclinal 
valleys  are  filled  with  Tertiary  and  Quaternary  detritus"  (a,  451). 
Soon  afterwards  Gilbert  concluded  that  the  individual  ranges 
were  the  carved  upper  parts  of  tilted  or  lifted  blocks,  resulting 
from  "  the  displacement  of  comparatively  rigid  bodies  of  strata  by 
vertical  or  nearly  vertical  faults"  (a,  50).  The  same  view  was 
elaborated  in  a  later  report  (b,  21-42).  Powell,  Button,  and  Rus- 
sell adopted  essentially  the  same  explanation.  King  also  seems  to 
have  recognized  the  validity  of  Gilbert's  conclusion,  for  in  1878 
he  modified  his  earlier  views  by  recognizing  frequent  faulting  at 
a  later  date  than  that  of  the  folding  by  which  the  great  anti- 
clinals  and  synclinals  had  been  produced  (£,  735).  None  of  these 
observers,  however,  gave  explicit  consideration  to  the  three  ele- 
ments necessarily  involved  in  the  problem  of  block  faulting ; 
namely,  the  pre-faulting  topography,  the  topographical  effect  of 
the  faulting,  and  the  work  of  erosion  on  the  faulted  blocks. 

One  of  the  latest  general  discussions  of  the  region  is  by  Spurr, 
in  whose  essay  a  review  of  earlier  writings  may  be  found.  This 
author  concludes  that  "  the  mountain  fronts  studied  are,  in  gen- 
eral, not  marked  by  great  faults,  and,  conversely,  that  the  ascer- 
tainable  faults  are  very  rarely  attended  by  simple  fault  scarps." 
He  therefore  rejects  Gilbert's  hypothesis  and  explains  the  Basin 
ranges  as  the  "  results  of  compound  erosion  active  since  Jurassic 
times,  operating  on  rocks  upheaved  by  compound  earth  move- 
ments which  have  been  probably  also  continuous  during  the  same 

725 


726  PHYSIOGRAPHIC  ESSAYS 

period."  It  is  further  suggested  that  the  ranges  were  probably 
differentiated  during  Cretaceous  time,  when  a  greater  precipita- 
tion is  assumed  to  account  for  their  dissection  :  "  subsequently 
the  climate  became  arid  and  the  water  supply  was  not  sufficient 
to  remove  the  detritus  from  the  valleys,  which  filled  up"  (265, 
266).  I  have  elsewhere  briefly  stated  the  reasons  why  this 
explanation  seems  unsatisfactory  (a). 

The  Basin  ranges  have  for  some  years  been  of  especial  interest 
in  systematic  physiography,  for  if  Gilbert's  explanation  of  them 
is  correct,  they  offer  unusually  simple  examples  of  mountain  up- 
lift and  sculpture ;  examples  that  may  be  adduced  as  relatively 
elementary  illustrations  of  the  difficult  group  of  mountains  in 
general,  and  that  may  therefore  be  with  propriety  presented  to 
beginners  for  introductory  practice  before  the  description  of  com- 
plicated mountain  ranges  is  undertaken.  This  opinion  was  con- 
firmed on  the  appearance  in  1884  of  Russell's  vivid  account  of 
the  faulted  lava-block  ranges  of  southern  Oregon ;  for  these  seemed 
to  be  even  simpler  and  younger  than  the  ranges  farther  south. 
Ranges  of  this  kind  are  of  a  further  interest  in  that  they  support 
in  a  certain  measure  the  more  primitive  theory  of  mountain-mak- 
ing ;  namely,  that  mountains  are  the  immediate  results  of  uplift, 
comparatively  little  modified  by  erosion,  while  the  intermediate 
troughs  are  the  effects  of  depression  ;  in  a  word,  that  dislocations 
of  the  earth's  crust  are  here  chiefly  responsible  for  the  observed 
relief  of  the  region,  and  that  the  part  played  by  erosion  is  sub- 
ordinate. It  is  now  generally  agreed  that  this  primitive  theory 
finds  little  support  in  such  ranges  as  the  Alps,  where  the  existing 
forms  of  peak  and  pass,  spur  and  valley,  are  the  product  of  exten- 
sive erosion  in  a  deformed  and  broadly  uplifted  mass.  A  recur- 
rence to  the  older  theory  in  explanation  of  the  ranges  of  the  Great 
Basin  is  therefore  a  wholesome  discipline. 

It  has  for  some  time  seemed  to  me  that  there  was  good  evi- 
dence for  regarding  the  Oregon  lava-block  ranges  as  types  of  the 
youngest,  most  elementary  mountain  forms  known  to  geographers, 
and  for  placing  the  ranges  of  the  Great  Basin  in  Utah  and  Nevada 
as  types  of  larger  and  more  maturely  sculptured  ranges,  appropri- 
ately following  the  introductory  examples  of  southern  Oregon. 
In  view  of  this  relation  of  the  Basin  ranges  to  the  problems  of 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        727 

systematic  physiography,  the  opportunity  of  seeing  some  of  them 
last  summer  was  especially  welcome,  even  though  the  time  that 
could  be  given  to  them  was  brief.  The  conclusion  reached  was 
that  faulting  has  recently  exercised  and,  indeed,  still  exercises  a 
dominant  control  over  the  uplift  of  all  the  larger  mountain  ranges 
observed,  but  that  erosion  has  greatly  modified  the  form  which 
would  be  produced  by  faulting  alone,  and  that  the  pre-faulting 
form  is  for  this  reason  generally  not  recognizable. 

Theoretical  Considerations.  It  seems  desirable  to  present  the 
observations  that  have  led  to  this  conclusion  in  an  order  that  is 
suggested  by  a  deductive  consideration  of  the  problem,  such  as  is 
necessarily  entertained  in  the  establishment  of  ideal  physiographic 
types  of  mountain  forms.  In  this  way  the  complete  ideal  types 
of  carved  block  mountains  may  be  first  carefully  conceived  and 
visualized  in  the  imagination,  all  their  essential  features  being 
systematically  developed.  The  observed  elements  of  form  may 
then  be  described  in  their  proper  relation  to  the  whole  of  which 
they  are  believed  to  be  but  parts. 

The  various  types  thus  conceived  in  the  imagination  must 
represent  all  the  hypotheses  by  which  the  facts  in  hand  may  be 
explained,  the  advantages  that  follow  from  a  due  consideration 
of  "multiple-working  hypotheses"  having  been  convincingly  set 
forth  by  Chamberlin.  In  publication,  however,  it  is  permissible 
to  give  relatively  little  space  to  those  hypotheses  which  have  been 
proved  incompetent  during  the  progress  of  an  investigation,  and 
to  set  forth  in  detail  only  the  one  which  has  gained  —  in  the 
author's  opinion  at  least  —  the  rank  of  a  successful  theory.  For 
this  reason  the  following  pages  are  chiefly  devoted  to  a  consider- 
ation of  the  Basin  ranges  as  dissected  fault-block  mountains. 

The  author  feels  that  some  apology  is  needed  for  his  writing 
on  a  field  where  his  own  observations  are  very  limited  in  com- 
parison to  those  of  others  who  have  a  much  wider  experience  in 
the  Cordilleran  region.  His  reason  for  adding  yet  another  essay 
to  the  already  abundant  literature  on  the  mountain  ranges  of  the 
Great  Basin  is  chiefly  that  the  articles  thus  far  published  have 
not  included  a  detailed  analysis  of  the  problem  in  hand,  and  in 
particular  that  the  effects  of  erosion  upon  the  faulted  mountain 
blocks  have  received  but  little  consideration.  Gilbert's  brief 


728  PHYSIOGRAPHIC  ESSAYS 

statement,  written  thirty  years  ago  as  the  result  of  his  first  west- 
ern expeditions  in  1871,  1872,  and  1873  (b,  40,  41),  is  hardly  more 
than  a  summary  of  conclusions.  Russell  explains  the  Basin  ranges 
as  having  been  "  formed  by  the  orographic  tilting  of  blocks  that 
are  separated  by  profound  faults  "  (a,  8),  and  leaves  the  erosion 
that  they  have  suffered  to  be  inferred.  Elsewhere,  when  describing 
the  West  Humboldt  range,  he  says  :  "  The  precipitous  moun- 
tain face  ...  is  in  reality  an  ancient  fault  scarp  of  grand  propor- 
tions, which  was  somewhat  eroded  before  the  existence  of  Lake 
Lahontan"  (#,  277) ;  but  "  somewhat  eroded  "  does  scanty  justice 
to  the  fine  sculpturing  of  this  range  as  shown  in  the  accompany- 
ing Plate  XLV.  Spurr  distinguishes  between  scarps  directly  due  to 
faulting,  and  scarps  due  to  the  erosion  of  a  long-ago  faulted  mass ; 
but  he  gives  no  explicit  discussion  of  the  forms  assumed  by  a 
simple  fault  scarp  as  it  undergoes  dissection ;  and  his  attention 
to  the  physiographic  features  of  the  Basin  ranges  in  general  is  so 
brief  that  he  implies  that  they  possess  an  intimate  correlation  of 
structure  and  form  by  saying  that  the  Appalachians  "  likewise 
consist  of  parallel  ridges  eroded  along  lines  of  folding"  (255). 

In  spite,  therefore,  of  the  many  descriptions  of  the  Basin  ranges 
that  have  been  published,  there  has  not  yet  appeared  any  detailed 
statement  of  the  theory  by  which  they  are  explained ;  the  essen- 
tial consequences  of  the  theory  have  not  been  explicitly  for- 
mulated ;  the  criteria  by  which  a  fault-block  mountain  may  be 
recognized  in  early  or  later  stages  of  dissection  have  not  been 
defined ;  and  it  is  to  supply  these  deficiencies  that  the  prepa- 
ration of  this  essay  was  undertaken. 

When  the  essay  had  reached  an  almost  completed  form,  the 
writer  had  the  advantage  of  hearing  the  Basin-range  problem 
discussed  by  Mr.  Gilbert  at  the  Washington  meeting  of  the 
Geological  Society  of  America,  in  January,  1903.  It  was  a  grati- 
fication to  find  that  the  plan  of  presentation  here  adopted  very 
closely  resembled  in  various  ways  the  treatment  offered  by  the 
originator  of  the  Basin-range  theory ;  it  was  at  the  same  time  an 
embarrassment  to  see  that  many  of  these  pages  would  be  hardly 
more  than  repetitions  of  Mr.  Gilbert's  report.  They  may,  how- 
ever, have  a  certain  value  in  so  far  as  they  show  that  independent 
study  leads  to  accordant  results. 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        729 


Ideal  Types  of  Fault-Block  Mountains.  There  are  two  chief 
types  of  fault-block  mountains  as  illustrated  in  Figs.  113  and 
114:  one  shows  what  may  be  called  a  tilted  block,  the  other  a 
lifted  block.  In  order  to  economize  space,  only  the  tilted-block  type 
will  be  here  con- 


sidered in  detail. 

The  most  char- 
acteristic features 
of  a  typical  tilted- 
block  mountain  in 
its  youth  or  early 
maturity  may  be 
summarized  in 


FIG.  113.   A  TILTED  BLOCK,  YOUTHFUL  STAGE 


Fig.  113  in  which  the  block,  ACE,  has  been  raised  and  more  or 
less  inclined.  The  upper  part,  BC,  of  the  faulted  face,  AC,  rises 
above  a  piedmont  plain  of  waste,  BD,  by  which  the  backward 
slope  of  an  adjoining  block  is  buried  ;  while  the  backward  slope 
of  the  block,  CE,  is  also  partly  buried  in  a  plain  of  waste,  FJ, 
which  meets  another  waste  plain  from  a  third  faulted  block,  EK. 
Certain  features  shown  in  the  figure  are  essential  to  the  type 
in  the  stage  of  erosion  here  considered.  The  fault-bounded  block, 
ACE,  must  present  a  back-sloping  surface,  CFE,  whose  form  be- 
fore the  faulting  occurred  is  now  more  or  less  modified  by  erosion 

in  its  exposed 
part,  CF,  and 
buried  under 
waste  in  its  de- 
pressed  part, 
FE.  The  lower 
part,  AB,  of  the 
faulted  face, 
ABC,  is  buried 
under  the  waste 

derived  from  the  exposed  and  more  or  less  dissected  part,  BC. 
Blocks  which  stand  so  high  that  the  trough  between  them  is 
now  dissected  instead  of  aggraded  are  not  here  considered.  Ex- 
amples of  this  kind  are  described  in  the  northern  Sierra  Nevada 
by  Diller  (12-16). 


FIG.  114.  A  LIFTED  BLOCK,  YOUTHFUL  STAGE 


730  PHYSIOGRAPHIC  ESSAYS 

Other  features  of  the  type  are  extremely  variable.  The  size, 
structure,  and  form  of  the  block  are  entirely  undefined.  Its 
upper  surface  may  have  been  in  the  pre-faulting  period,  a  pene- 
plain worn  down  on  ancient  schists  ;  a  mountain  area  of  folded  or 
faulted  strata  more  or  less  subdued  by  erosion ;  a  series  of  hori- 
zontal and  slightly  dissected  aqueous  or  igneous  strata ;  or  any- 
thing else.  The  block  faulting  may  be  on  a  large  or  small  pattern  ; 
of  regular  or  irregular  arrangement ;  reaching  over  an  extensive 
or  a  restricted  area ;  of  great  or  little  displacement ;  and  with 
much  or  little  tilting. 

The  displacement  may  be  slow  or  rapid,  uniform  or  variable 
in  rate,  of  brief  duration  or  long  continued,  of  remote  or  recent 
beginning  and  ending ;  it  may  vary  greatly  in  amount  along  the 
fault  line,  diminishing  to  its  end  ;  as  faulting  continues,  the  length 
of  the  block  may  increase,  and  its  end  will  thus  vary  in  position. 
The  faults  may  be  simple  or  complex ;  the  faulted  front  of  a  block 
may  be  clean  cut,  stepped,  or  shattered ;  the  fault  line  along  the 
mountain  base  may  be  essentially  indifferent  to  the  structure  of 
the  block,  for  the  fault  may  be  of  deep-seated  origin  and  not  nec- 
essarily guided  by  the  preexistent  foliation,  stratification,  folding, 
or  faulting  that  is  seen  in  the  upper  part  of  the  block.  The  fault 
surface  may  be  nearly  a  plane  or  a  conspicuously  curved  surface, 
but  from  all  that  is  known  of  faults  it  cannot  possess  sharp  or 
exaggerated  irregularities  such  as  are  seen  in  the  septa  of  an  am- 
monite. The  uplift  and  tilting  may  vary  widely  in  the  different 
examples  of  a  single  district.  Appropriate  to  all  these  variable 
elements,  the  present  form  of  a  faulted  block  may  exhibit  little 
or  much  modification  by  erosion ;  little  modification  being  con- 
sistent with  rapid  and  recent  faulting  of  a  resistant  block  in  very 
arid  climate  ;  much  modification  being  consistent  with  slow  and 
ancient  faulting  of  a  weak  block  in  a  climate  of  sufficient  rainfall 
to  produce  active  erosion.  In  a  block  whose  length  has  been 
increasing  during  a  long  time  of  increasing  displacement,  it  would 
be  reasonable  to  expect  a  mature  dissection  near  the  middle  of 
the  block  to  give  way  to  young  dissection  near  the  ends  of  the 
block  ;  for  the  middle  part  will  have  been  long  exposed  to  erosion, 
while  the  ends  will  have  been  but  lately  uplifted.  The  pre-faulting 
form  of  the  block  surface  will  usually  be  longest  preserved  near 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        731 


the  base  of  its  exposed  back  slope,  CF>  and  the  form  due  immedi- 
ately to  faulting  will  be  best  seen  near  the  base  of  the  front,  CB. 
As  long  as  the  faulting  and  tilting  continue,  strong  relief  may 
be  maintained  ;  but  after  displacement  ceases,  erosion  will  advance 
without  more  hindrance  than  is  offered  by  the  resistance  of  the 
rocks ;  it  will  slowly  subdue  the  earlier  t  relief  to  rounded  forms, 
and  still  more  slowly  widen  the  valleys  and  consume  the  inter- 
vening hills  as  the  forms  of  old  age  (Fig.  115)  are  realized.  In  a 
late  stage  of  degradation  the  mountain  mass  will  be  invaded  by 
numerous  flat-floored,  branching  valleys  between  low,  rounded 
forking  spurs.  The  valleys  will  then  be  largely  adjusted  to  the 
weaker  rock  structures,  while  the  fading  ridges  will  stand  longest 
where  upheld  by  the 
resistant  structures. 
The  mountain  base, 
an  irregular  line,  will 
have  no  close  rela- 
tion to  the  path  of 
the  fault,  and  the 
slope  between  the 


FIG.  115.   A  TILTED  BLOCK,  OLD  STAGE 


mountain  base  and  the  fault  line  will  carry  a  thin  and  discontin- 
uous veneer  of  waste  on  a  planed  rock  floor.  It  would  probably 
be  impossible  to  distinguish  the  residuals  of  tilted  and  lifted 
blocks  in  a  late  stage  of  erosion. 

Place  and  Value  of  Deduction.  It  is  important  here  to  empha- 
size two  general  considerations.  First,  the  details  of  form  appro- 
priate to  any  desired  special  case  under  the  ideal  type  should  be 
deduced  with  as  much  completeness  and  definiteness  as  possible. 
As  long  as  the  details  of  a  theoretical  form  are  vaguely  conceived, 
the  observer  will  be  unable  to  give  his  theory  a  rigorous  test ;  its 
consequences  will  be  so  indefinite  that  he  can  hardly  say  whether 
they  are  confirmed  or  contradicted  when  he  confronts  them  with 
the  appropriate  facts  of  observation.  It  is  particularly  important 
that  deduction  should  not  be  postponed  till  after  the  field  work  is 
"completed"  and  after  the  field  is  left.  The  two  processes  of 
observation  and  deduction  should  go  on  together  in  the  field,  each 
aiding  the  other,  if  the  investigator  would  avoid  as  far  as  possible 
the  disappointment  of  finding  afterwards  that  the  field  records 


732  PHYSIOGRAPHIC  ESSAYS 

are  deficient  in  some  particular  point  where  fuller  record  would 
have  been  of  critical  value  in  testing  a  deduction.  Memory  may 
sometimes  supplement  written  record,  but  it  is  notoriously  danger- 
ous to  trust  to  unwritten  notes.  In  my  own  experience,  however, 
careful  deduction  is  more  difficult  than  observation  in  the  field, 
but  it  is  greatly  aided  by  deliberate  thinking  and  writing  while 
the  facts  are  before  the  eyes. 

Second,  it  must  not  be  assumed  that  a  theory  gains  support 
because  its  consequences  can  be  definitely  deduced.  However 
accurately  one  may  argue  out  the  details  of  form  appropriate  to 
a  certain  stage  in  the  dissection  of  a  faulted  mountain  block,  the 
theory  of  block  faulting  becomes  a  demonstrated  occurrence  only 
when  the  sharply  deduced  consequences  of  the  theory  are  shown 
to  accord  with  closely  determined  facts  of  observation. 

Not  only  is  it  important  that  an  investigation  should  give  equal 
attention  to  deduction  and  induction  :  it  is  essential  to  clear 
presentation  that  both  phases  of  inquiry  should  be  sufficiently 
published.  It  is  otherwise  almost  impossible  for  the  reader  to 
discriminate  between  sound  and  unsound  conclusions.  It  is  con- 
ceivable that  an  able  observer  should*  patiently  collect  and  record 
a  multitude  of  facts,  and  that  he  should  very  imperfectly  set  forth 
the  reasons  that  lead  him  to  the  announced  explanation  of  the 
facts.  The  hurried  reader  may  in  such  a  case  quote  the  announced 
explanation  and  accept  it,  if  he  wishes,  on  the  authority  of  the 
writer ;  but  the  more  critical  reader  will  wish  to  make  his  own 
measure  of  the  validity  of  the  announced  conclusion,  and  this  he 
will  find  difficult  in  the  absence  of  explicit  announcement  of  the 
method  of  reaching  it.  It  is  particularly  important  to  consider 
the  deductive  side  of  any  problem  in  which  there,  is  substantial 
agreement  among  different  observers  as  to  the  facts  directly 
observable,  but  in  which  there  is  difference  of  opinion  as  to  the 
explanation  of  the  facts  ;  for  in  such  a  case  the  correct  solution 
of  the  problem  turns  essentially  on  the  validity  of  the  deductions 
by  which  the  unobservable  facts  of  the  past  are  brought  into 
mental  vision. 

It  may  not  be  amiss  to  point  out  that  the  investigator's 
effort  in  all  such  problems  as  the  one  here  in  hand  is  simply 
to  supplement  the  directly  observable  present  facts  by  the 


MOUNTAIN   RANGES  OF  THE  GREAT  BASIN        733 

discovery  of  the  unobservable  past  facts,  so  that  the  entire 
phenomenon  shall  become  known.  If  observers  of  sufficient 
penetration  had  been  present  in  the  Great  Basin  during  all  the 
formative  period  of  each  mountain  range  now  seen,  their  records 
of  unobserved  fact  might  give  a  complete  account  of  all  the  proc- 
esses involved  ;  and  it  would  then  be  perfectly  clear  whether  the 
mountain  ranges  were  carved  fault  blocks  or  not.  In  the  neces- 
sary absence  of  such  observers  we  try  to  replace  their  records  by 
our  discoveries,  and  although  our  method  of  discovery  necessarily 
has  recourse  to  the  imagination,  the  phenomena  that  we  success- 
fully discover  are  facts  of  only  a  slightly  different  order  from 
those  of  direct  observation.  We  see  certain  forms  imprinted  in 
stratified  rocks,  and  by  reasonable  mental  process  arrive  at  the 
conclusion  that  these  are  the  remains  of  once  living  organisms. 
We  see  two  groups  of  similar  strata  in  similar  sequence,  and  by 
reasonable  mental  process  reach  the  belief  that  their  present  dis- 
continuity is  the  result  of  what  is  called  faulting.  In  both  these 
cases  the  inferred  explanation  is  accepted  by  most  geologists  as 
of  essentially  the  same  order  of  verity  as  the  observed  fact,  be- 
cause it  has  now  stood  the  test  of  repeated  and  minute  scrutiny. 
In  the  case  of  the  Basin  ranges,  interpreted  as  carved  fault  blocks, 
many  geologists  are  at  present  by  no  means  disposed  to  attach 
equal  value  to  the  existing  facts  of  structure  and  form  reached 
by  direct  observation  and  the  supposed  past  facts  of  dislocation 
reached  by  mental  inference.  It  is  therefore  appropriate  that 
special  attention  should  be  here  given  to  the  method  of  inference 
by  which  the  past  facts  are  resurrected. 

It  is  the  application  of  the  combined  inductive  and  deductive 
method  here  sketched,  although  always  applied  less  consciously 
and  completely  in  the  field  than  could  be  wished,  that  has  satis- 
fied me  of  the  essential  correctness  of  the  theory  which  explains 
the  larger  ranges  of  the  Great  Basin  as  well-dissected  blocks  of 
long-maintained  faulting,  continued  into  recent  time. 

Evidence  of  Faulting  along  the  Mountain  Base.  The  first  ele- 
ments for  consideration  in  this  problem  are  those  which  should, 
in  a  type  example  of  a  long-faulted,  well-dissected  mountain  block, 
be  expectably  associated  with  the  occurrence  of  a  fault  along  the 
mountain  base. 


734  PHYSIOGRAPHIC  ESSAYS 

The  simplest  and  most  manifest  element  of  this  kind  is  a  nearly 
straight  or  but  moderately  curved  base-line  (Fig.  1 1 3)  passing  in- 
differently across  or  obliquely  along  the  structure  of  the  moun- 
tain mass  which  rises  rather  abruptly  and  continuously  on  one 
side,  while  a  sloping  plain  of  waste  is  spread  out  on  the  other. 
The  simple  continuity  of  the  base-line  and  the  complete  absence 
of  rock  outcrops  on  one  side  of  it  are  essential  consequences  of 
long-continued  block  faulting,  and  are  at  the  same  time  not 
characteristic  of  any  other  available  geological  process.  As 
Emmons  wrote  nearly  thirty  years  ago,  one  cannot  "  imagine  an 
erosion  which  would  leave  an  abrupt  wall  of  7500  feet  in  height 
on  one  side  of  a  valley  nearly  twenty  miles  wide  "  (345).  Hence, 
wherever  these  theoretical  consequences  are  borne  out  by  facts 
of  direct  observation,  block  faulting  is  thereby  given  so  high  a 
degree  of  probability  while  other  processes  are  rendered  so  highly 
improbable  that  the  theory  of  block  faulting  may  be  looked  upon 
as  well  introduced,  at  least. 

The  best  examples  that  came  under  my  observation  of  actual 
forms  which  match  these  preliminary  members  of  the  whole 
series  of  deduced  type  forms  were  »ot  among'  the  Basin  ranges 
proper,  but  along  the  bordering  Wahsatch  mountain  front,  by 
which  the  Great  Basin  is  limited  on  the  east.  The  mountain  base 
near  Provo  and  near  Ogden  deserves  careful  study  in  this  respect. 

The  Wahsatch  range  is  divided  into  several  local  mountain 
groups  by  the  canons  of  streams  that  rise  a  number  of  miles 
east  of  the  line  of  higher  summits  and  flow  westward  to  Salt 
Lake  Basin.  In  the  neighborhood  of  Provo  the  canons  are  those 
of  Spanish  fork,  Hobble  creek,  and  Provo  river,  between  which 
the  mountain  groups  may  be  called  the  Spanish  peaks  Wahsatch, 
and  the  Provo  peaks  Wahsatch,  or,  more  briefly,  the  Spanish  and 
the  Provo  Wahsatch  (Emmons,  340,  344). 

Close  by  Provo,  where  my  party  had  the  most  leisure  for  atten- 
tion to  this  problem  and  where  we  had  the  advantage  of  guidance 
by  Professor  E.  H.  Hinckley  of  the  academy  in  that  city,  the  expec- 
tations of  theory  are  extraordinarily  well  supported  by  the  facts. 
The  mountains  spring  boldly  from  the  plain  ;  their  base-line 
breaks  obliquely  across  the  tilted  and  folded  rocks  of  the  moun- 
tain mass ;  the  occurrence  of  a  base-line  fault  is  explicitly  stated 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        735 

by  Emmons  (345).  We  made  an  excursion  up  Rock  canon  to  a 
mid-monoclinal  ridge  back  of  the  frontal  summits,  and  returned 
by  Slate  canon.  There  are  some  indications  of  faults  in  the 
longitudinal  valleys  between  the  monoclinal  ridges  (Emmons, 
345,  348),  but  nothing  at  present  known  serves  to  give  date  to 
these  faults,  should  they  be  proved  to  occur.  Fig.  116  shows 
the  generalized  structure  thus  determined  :  an  anticlinal  axis  lies 
near  the  western  base  of  the  mountains  opposite  Provo,  while  a 
great  monocline,  the  eastern  half  of  the  incomplete  anticline,  con- 
stitutes the  rest  of  the  range.  Farther  south  the  anticline  is  not 
seen  at  the  mountain  base.  The  rocks  in  the  anticlinal  axis  are 
said  to  be  mid-Paleozoic  ;  those  of  the  crests  are  Carboniferous 
(Emmons,  345,  346);  farther  east  the  maps  of  the  4Oth  parallel 


w 


FIG.  116.  ROUGH  CROSS  SECTION  OF  THE  PROVO  WAHSATCH,  LOOKING  NORTH 

survey  indicate  Mesozoic  strata.  West  of  the  mountain  base  no 
rocks  are  seen  in  place  ;  the  gravel  beaches  and  deltas  of  lake 
Bonneville  descend  to  the  alluvial  plain  that  slopes  under  the 
shallow  waters  of  Utah  lake. 

About  twelve  miles  southeast  of  Provo,  the  Spanish  Wahsatch, 
lying  next  north  of  Spanish  fork  canon,  is  even  more  emphatic 
in  its  testimony  for  block  faulting.  Its  rock  layers  are  nearly 
horizontal,  or  dip  gently  eastward.  Some  significant  details  of 
its  form  will  be  considered  later. 

The  Wahsatch  near  and  northwest  of  Ogden  presents  several 
significant  features,  even  when  seen  only  from  a  railroad  train. 
Its  base-line  is  here  of  moderate  curvature,  and  manifestly  trav- 
erses various  structures,  as  indicated  both  by  form  and  by  color. 
The  mountain  front  rises  abruptly  and  continuously  from  the  base- 
line, except  for  brief  interruptions  in  narrow-mouthed  canons. 

The  features  of  this  range  and  of  several  others  farther  west, 
as  seen  from  the  passing  train,  were  so  accordant  with  the 


736  PHYSIOGRAPHIC  ESSAYS 

features  more  deliberately  observed  near  Provo  that  it  seemed  to 
me  one  could  hardly  regard  them  as  other  than  carved  fault  blocks  ; 
but  while  observations  from  a  train  may  have  a  high  value  to  the 
observer,  I  am  well  aware  that  they  will  not  be  regarded  as  con- 
vincing by  others,  especially  not  by  those  whose  habitual  work 
in  paleontology,  petrography,  or  minute  stratigraphy  has  given 
them  no  acquaintance  with  the  value  of  large  elements  of  form 
in  physiographic  problems,  even  though  these  elements  be  only 
hastily  observed  from  a  car  window. 

During  a  stage  ride  northward  from  Winnemucca,  Nevada,  into 
southern  Oregon,  I  passed  the  Santa  Rosa  and  Pine  Forest  ranges, 
both  of  which  exhibited  very  clearly  the  gently  curving  base-line, 
regardless  of  rock  structure,  and  the  bold  mountain  front,  con- 
tinuous except  for  sharp-cut  canons,  that  are  essentially  charac- 
teristic of  carved-block  mountains.  The  western  face  of  Jackson 
range  near  its  northern  end  had  the  same  appearance,  but  this 
was  very  imperfectly  seen.  Further  details  concerning  the  first 
two  of  these  ranges  are  given  in  a  later  section. 

The  Base-Line  of  Residual  Mountains.  It  may  be  worth  while 
to  state  at  this  stage  of  the  discussion  the  reasons  for  rejecting 
the  theory  that  the  mountain  ranges  just  described  are  the  resid- 
uals of  much  larger  masses,  of  which  the  vanished  parts  have 
been  removed  by  erosion.  These  reasons  are  found,  not  at  all 
in  the  incompetence  of  erosion  to  wear  away  mountains,  but  in 
the  impossibility  of  explaining  the  forms  of  the  mountain  ranges 
above-named  as  the  residuals  of  much  larger  masses.  There  are 
numerous  examples  in  which  general  sub-aerial  erosion  has  suf- 
ficed to  remove  mountains  more  or  less  completely,  but  no  ex- 
amples in  which  the  residuals  of  half-consumed  mountains  exhibit 
the  features  above  described  as  characteristic  of  certain  Basin 
ranges.  Several  special  cases  may  be  considered. 

The  only  residual  mountains  known  to  physiographers  as  having 
a  relatively  continuous  mass  and  rectilinear  base  are  those  in 
which  structure  controls  form,  as  in  the  stratified  Appalachians 
of  Pennsylvania  and  Virginia.  There  the  ridges  of  resistant  sand- 
stone rise  between  rolling  lowlands  of  weaker  strata ;  the  ridges 
are  occasionally  cut  through  in  water  gaps,  but  between  the  gaps 
they  frequently  present  a  continuous  mass  sloping  evenly  to  a 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN 


737 


nearly  rectilinear  base.  When  the  strata  bend,  the  ridges  turn  ; 
when  the  strata  are  cut  off  by  a  fault,  the  ridges  end.  Structure 
is  perfectly  expressed  in  form.  The  same  rule  applies  to  the  trap 
ridges  of  the  Triassic  areas  of  Connecticut,  New  Jersey,  and 
Pennsylvania,  but  the  rule  clearly  enough  does  not  apply  to  the 
Wahsatch  mountains  and  the  other  Basin  ranges  above  named. 
Residual  mountains  whose  survival  is  not  dependent  on  con- 
trasts of  rock  resistance  so  striking  as  those  of  the  Appalachians, 
and  whose  structure  is  relatively  massive,  are  well  illustrated  in 
the  crystalline  Appalachians  of  North  Carolina  and  Georgia. 
In  mountains  so  old  as  these,  it  is  to  be  presumed  that  the 
valleys  have  generally  come,  by  a  process  of  long-sought  adjust- 
ment, to  follow  the  somewhat  weaker  rocks,  while  the  mountains 
represent  the  more  resistant  masses.  None  of  these  mountains, 
however,  have  a 


bold  descent  to  a 
nearly  rectilinear 
base  ;  all  of  them 
give  forth  spurs 
which,  as  a  rule, 
slope  more  and 
more  gradually 
as  they  fade  away 
on  the  valley  low- 
lands, while  branch  valleys  enter  between  the  spurs  far  into 
mountains.  The  mountain  base-line  is  sinuous  and  ill-defined. 

One  of  the  most  remarkable  of  these  many  residuals  is  a  group 
of  radiating  spurs  that  culminate  in  Big  Bald  mountain  in  the 
older  Appalachians  of  northern  Georgia  (Ellijay  map  sheet).  The 
spurs  have  a  notably  stellate  arrangement  between  open  centrif- 
ugal valleys,  showing  that  the  mountain  is  to-day  the  mere  skel- 
eton of  a  once  much  larger  body ;  its  emaciated  form  is  highly 
suggestive  of  the  gnawing  erosion  which  it  has  so  long  suffered. 

A  good  example  for  contrast  with  the  Basin  ranges  is  found 
in  the  strong,  east-facing  escarpment  known  in  northern  North 
Carolina  and  southern  Virginia  as  the  "  Blue  Ridge."  The  escarp- 
ment, AB  (Fig.  117),  is  evidently  retreating  westward,  for  it  is 
simply  the  headwater  slope  of  the  short-course  Atlantic  rivers, 


FIG.  117.   THE  BLUE  RIDGE  ESCARPMENT,  NORTH 
CAROLINA,  LOOKING  NORTH 


738  PHYSIOGRAPHIC  ESSAYS 

which  are  actively  capturing  drainage  area  from  the  higher-lying 
headwaters,  AD,  of  the  much  longer  rivers  of  the  Mississippi  sys- 
tem. Viewed  in  a  very  general  way,  as  on  a  small  scale  map,  the 
base  of  the  scarp  is  of  moderate  curvature,  and  its  slope  is  essen- 
tially independent  of  structure  ;  hence  in  both  these  general  fea- 
tures it  might  be  said  to  resemble  the  face  of  a  Basin  range.  But 
when  viewed  in  detail,  the  base  of  the  escarpment  is  sinuous 
in  a  high  degree,  with  numerous  branching  spurs  that  advance 
between  well-carved  amphitheaters ;  the  spurs  gradually  fade  out 
forward  instead  of  being  abruptly  terminated  at  a  well-defined 
base-line,  as  is  so  persistently  the  case  with  the  above-described 
ranges  of  Utah  and  Nevada.  In  some  cases  the  spurs  run  far 
forward,  forming  ridges  of  undulating  outline,  by  which  embay- 
ments  Of  the  piedmont  lowland  are  divided.  The  contrast  of  the 
Blue  Ridge  escarpment  and  the  Basin  ranges  is  therefore  extremely 
instructive.  The  topographical  maps  of  the  North  Carolina  moun- 
tains are  worth  examining  in  this  connection  :  Wilkesboro,  Cran- 
berry, Mt.  Mitchell,  and  Pisgah  (North  Carolina),  and  Hillsville 
(Virginia)  sheets  afford  the  best  illustrations. 

The  only  conditions  under  which  residual  mountains  have  a 
well-defined,  moderately  curved  base-line  is  where  they  are  cut 
across  by  a  master  river,  or  laterally  attacked  by  the  waves  of  a 
vigorous  sea ;  but  these  conditions  are  so  manifestly  inapplicable 
to  the  region  of  the  Basin  ranges  that  they  need  no  consideration 
here,  except  in  so  far  as  they  suggest  that  a  trenchant  cause  is 
needed  to  explain  the  well-defined  base-line  to  which  the  ranges 
descend. 

Residual  Mountains  in  the  Great  Basin.  There  are,  however, 
some  excellent  examples  of  residual  mountains  among  the  Basin 
ranges.  Those  that  I  saw  are  of  much  less  height  than  the  ranges 
thus  far  described.  Their  forms  are  thoroughly  subdued.  They 
have  no  well-defined  and  moderately  curved  base-line,  but  descend 
in  branching,  sprawling,  fading  spurs,  which  interlock  with  broad, 
flat-floored,  branching  valleys.  The  contrast  of  these  nearly  worn- 
out  mountains  with  the  more  vigorous  forms  previously  consid- 
ered is  most  striking,  yet  it  is  entirely  conceivable  that  the 
contrast  may  be  due  simply  to  stage  of  development  and  not  to 
difference  of  origin.  It  has  already  been  shown  that  the  late 


MOUNTAIN   RANGES  OF  THE  GREAT  BASIN        739 

stage  of  dissection  of  a  fault-block  mountain  would,  long  after 
faulting  had  ceased,  present  essentially  such  worn-out  forms  as 
are  here  described,  for  the  sharp  definition  of  the  base-line  would 
be  lost  after  faulting  had. weakened  and  stopped.  On  the  other 
hand,  the  old  residuals  of  massive  mountains  of  any  other  kind 
would  also  present  these  worn-out,  sprawling  forms.  There  are, 
indeed,  no  tests  by  which  the  two  kinds  of  old  mountains  can 
be  easily  distinguished. 

Several  examples  of  residual  ranges  in  the  Great  Basin  were 
noted  as  follows  :  North  of  Tecoma,  Central  Pacific  Railroad, 
there  are  mountains  of  moderate  relief,  whose  rounded,  branch- 
ing spurs  descend  gradually  to  low,  sprawling,  dwindling  termi- 
nals between  wide-open,  waste-floored  valleys.  The  fading  spurs 
and  open  valleys  interlock  on  a  very  sinuous  line.  These  well- 
defined  features  gain  an  added  value  by  their  contrast  with  the 
Ombe  and  Ute  ranges,  south  and  west  of  Tecoma  :  both  of  these 
are  of  strong  relief,  with  relatively  rectilinear  base-lines  on  the 
sides  toward  the  railroad.  Their  valleys  are  steep-sided  and  nar- 
row-floored, causing  but  little  interruption  in  the  otherwise  con- 
tinuous mountain  front.  Nevertheless,  these  higher  ranges  have 
been  abundantly  carved,  so  that  their  peaks  and  spurs  preserve 
no  indication  of  an  original  block  form  ;  and  no  signs  of  modern 
faulting,  elsewhere  so  easily  recognizable  from  the  train,  were 
here  visible. 

North  of  Omar  there  is  a  typical  subdued  mountain  mass, 
whose  dwindling  spurs  interlock  with  open  valleys.  This  exam- 
ple was  strongly  contrasted  with  the  lofty  Humboldt  range, 
south  of  Wells ;  here  the  snow-patched  peaks  descended  by 
strong  slopes  to  a  relatively  rectilinear  base-line  on  the  northwest. 

Northeast  of  Golconda,  Nevada,  a  low  range  descends  to  a 
very  ragged  base,  one  of  the  best  examples  of  the  kind  that  my 
trip  discovered.  Its  description  would  involve  a  repetition  of 
what  has  just  been  said  for  other  similar  ranges,  though  the  de- 
scription here  might  be  somewhat  more  emphatic  than  before. 

Another  example  of  this  class  is  a  small,  unnamed  range,  about 
forty  miles  north  of  St.  George,  Utah.  Its  spurs  are  long  drawn 
out,  with  concave  profiles  toward  their  base ;  its  valley  mouths 
are  wide  open,  holding  broad,  waste-covered  slopes.  Its  base-line 


740  PHYSIOGRAPHIC  ESSAYS 

is  sinuous  and  indefinite,  in  the  strongest  contrast  to  the  simple 
and  definite  base-line  of  the  Spanish  Wahsatch. 

The  Canons  and  Ravines  of  Block  Mountains.  If  we  now 
return  to  the  consideration  of  the  higher  Basin  ranges,  it  seems 
undeniable  that  faulting  gives  a  much  better  explanation  of  their 
base-line  than  can  possibly  be  given  by  erosion.  Indeed,  erosion 
can  be  appealed  to  for  the  removal  of  the  missing  mountain 
masses  only  so  long  as  the  processes  and  results  of  erosion  are 
looked  upon  as  arbitrary  and  beyond  reduction  to  those  general- 
izations known  as  natural  laws.  The  day  has  passed  when  this  is 
permissible.  Erosion,  whether  sub-aerial  or  littoral,  fluvial,  gla- 
cial, or  aeolian,  proceeds  systematically  through  a  series  of  stages; 
and  while  there  is  still  more  to  be  learned  than  is  now  known 
regarding  the  progress  of  mountain  sculpture,  enough  is  already 
safely  understood  to  exclude  the  resort  to  erosion  in  general  as 
a  ready  means  of  accounting  for  any  desired  result.  It  remains, 
however,  to  be  seen  whether  not  only  the  base  but  the  face  of 
the  Basin  ranges  is  consistent  with  the  theory  of  block  faulting. 
The  form  of  the  valleys  that  are  carved  in  the  monntain  face 
will  be  first  considered,  and  after  this  the  form  of  the  spurs 
between  the  valleys. 

It  follows  from  the  scheme  graphically  represented  in  Fig.  113 
that  a  very  rapid  and  modern  faulting  of  a  very  resistant  rock 
mass  in  a  very  conservative  climate  would  produce  a  mountain 
block  having  a  notably  smooth  fault-face  or  escarpment  along  its 
front.  On  the  other  hand,  the  gradual  and  long-continued  fault- 
ing of  a  weak  rock  mass  in  a  destructive  climate  would  produce 
a  mountain  block  having  well-developed  ravines  and  canons  whose 
erosion  had  been  accomplished  during  the  progress  of  the  fault- 
ing. The  essential  characteristic  of  such  ravines  would  be  a 
V-like  cross  section  even  down  to  the  ravine  mouths  ;  and  as 
long  as  the  uplifting  of  the  mountain  block  actively  continues, 
the  streams  that  are  dissecting  it  cannot  widen  their  valley  floors. 
Indeed,  many  of  the  smaller  streams  might  be  unable  under  such 
conditions  to  attain  a  graded  slope  even  in  weak  rocks,  and  their 
channels  would  be  marked  by  rapids  near  the  base-line  of  the 
mountain,  where  the  V-ravine  would  suddenly  open  upon  an  allu- 
vial fan,  sloping  gently  forward  to  the  waste-covered  piedmont 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        741 

plain.  It  is  only  after  faulting  has  ceased  that  the  streams  can 
advance  in  an  uninterrupted  progress  toward  mature  develop- 
ment and  widen  their  valley  floors  toward  the  mountain  front ; 
and  only  after  faulting  has  long  ceased  can  the  valley  floors  be 
so  far  developed  as  to  leave  nothing  but  residual  skeletons  of 
the  original  mountain  block  between  them.  Variations  in  rate 
of  faulting  and  in  resistance  of  rock  masses  would  produce  many 
corresponding  variations  in  ravine  forms,  many  of  which  may  be 
easily  deduced,  but  none  of  which  demand  immediate  consideration. 

The  points  that  need  special  emphasis  in  this  connection  are 
that  the  characteristic  form  of  ravines  and  canons,  carved  in  a 
faulted  mountain  block  during  the  progress  of  a  long-continued 
and  still  active  faulting,  can  be  reasonably  determined  by  deduc- 
tion ;  that  these  forms  are  well  specialized  ;  and  that  their  most 
notable  peculiarity  is  the  persistence  of  a  V-section  down  to  the 
mountain  base,  where  the  steep-walled  ravine  or  canon  suddenly 
opens  upon  a  gravel  fan  that  slopes  forward  to  the  wide  pied- 
mont plain.  It  goes  without  saying  that  this  peculiarity  of 
canon  form  is  impossible  in  a  residual  mountain,  carved  by  the 
extensive  erosion  of  a  once  much  larger  mass,  unless  the  most 
special  conditions  conspire  to  produce  it.  Such  conspiracy  is 
found,  as  has  been  said,  in  the  stratified  Appalachians,  where 
the  belts  of  resistant  sandstone,  interstratified  with  much  weaker 
shales  and  limestones,  now  stand  in  relief  as  residual  mountains 
in  which  the  streams  and  rivers  have  cut  sharp  V-section  ravines 
and  notches.  The  resistance  of  the  sandstones,  on  which  the 
survival  of  the  sharply  limited  mountain  ridge  depends,  is,  there- 
fore, also  the  cause  of  the  narrowness  of  the  ravines  and  notches 
cut  in  it  by  the  streams  ;  and  it  may  be  added  that  the  sharpness 
of  these  forms  is  in  part  due  to  the  relatively  recent  uplift  that 
the  middle  Appalachian  belt  has  suffered. 

All  the  higher  Basin  ranges  that  I  saw  in  the  summer  of  1902 
are  characterized  by  sharp-cut  V-section  ravines  and  canons,  nar- 
row-floored and  steep-walled  down  to  their  very  mouths.  All 
these  canoned  ranges  are  so  unlike  in  structure  to  the  ridges 
of  the  stratified  Appalachians  that  it  is  utterly  out  of  the  ques- 
tion to  explain  the  former  by  the  theory  that  is  appropriate  for 
the  latter. 


742  PHYSIOGRAPHIC  ESSAYS 

Rock  canon  in  the  Wahsatch,  near  Provo,  has  a  narrow  gravel 
plain  near  its  mouth,  probably  the  result  of  delta  building  in 
front  of  the  mountain  base  during  the  presence  of  lake  Bonne- 
ville  ;  but  after  going  up  the  canon  a  few  hundred  feet,  its 
stream  is  found  cascading  on  the  more  resistant  strata,  whose 
rising  outcrops  form  prominent  ribs  on  the  steep  canon  wall. 
The  same  features  are  observable  in  Slate  canon,  three  miles 
farther  south,  except  that  the  stream  here  being  smaller,  its 
descent  is  steeper,  and  it  has  accumulated  hardly  any  gravels 
upstream  from  its  Bonneville  delta  on  the  mountain  front.  The 
beds  of  both  these  streams  have  a  rapid  descent,  and  are  not 
cut  down  as  low  at  the  canon  mouth  as  might  be  expected  in 
view  of  the  much  lower  level  of  the  broad  piedmont  plain  a  little 
way  forward  from  the  mountain  base.  Some  detention  of  their 
down-cutting  must  be  ascribed  to  the  temporary  rises  of  the  local 
base-level  during  Bonneville  time,  and  to  the  work  of  removing 
high-level  delta  gravels  in  post-Bonneville  time  ;  but  this  cause 
of  detention  does  not  seem  nearly  sufficient  to  account  for  the 
height  of  the  stream  beds  over  the  plain.  Hence,  not  only  the 
steepness  of  the  canon  walls,  tfhe  narrowness  of  thei'r  floors,  and 
the  rapid  descent  of  their  stream,  but  also  the  relatively  high 
level  of  their  mouths  suggest  recent  uplift  of  the  mountain  block. 

The  general  form  of  these  two  steep-walled  canons  suggests 
not  only  that  the  up-faulting  of  the  mountain  block  has  been  con- 
tinued into  relatively  recent  time,  but  that  the  uplift  of  the  block 
by  an  amount  equal  to  the  height  of  the  summits  over  the  base 
(in  the  Provo  Wahsatch)  has  been  accomplished  since  the  latter 
part  of  Tertiary  time.  The  canons  have  a  much  younger  expres- 
sion than  that  of  the  narrow  valleys  in  the  uplands  of  southeast- 
ern Pennsylvania,  for  there  the  streams  have  formed  narrow  flood 
plains  and  the  valley  sides  are  for  the  most  part  smoothly  graded 
even  in  crystalline  rocks  ;  yet  the  elevation  of  these  uplands  is 
not  of  remote  date.  If  it  is  thought  unsafe  to  make  a  comparison 
between  canons  in  the  arid  interior  basin  of  Utah  and  young  val- 
leys in  our  better-watered  Atlantic  slope,  the  Wahsatch  canons 
with  their  perennial  streams  may  be  compared  with  the  dry  side 
canons  of  the  Colorado  canon  in  Arizona.  The  expression  of  the 
two  is  much  the  same,  allowance  being  made  for  the  unlike  attitude 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        743 

of  the  rocks.  The  chief  difference  between  these  two  groups 
of  canons  is  this :  those  of  the  Arizona  plateaus  were  cut  down 
in  a  rising  plateau  mass  by  intermittent  wet-weather  streams 
working  with  respect  to  the  sinking  local  base-level,  the  intrench- 
ing Colorado ;  those  of  the  Wahsatch  were  cut  down  in  a  rising 
mountain  mass  by  more  persistent  streams  working  with  respect 
to  a  relatively  fixed  local  base-level.  The  erosion  of  the  Arizona 
canons,  trunk  and  branch,  cannot  have  been  begun  earlier  than 
the  latter  part  of  Tertiary  time  ;  the  erosion  of  the  Wahsatch 
canons  may  well  have  had  an  even  later  beginning.  The  date 
assigned  to  the  Wahsatch  fault  by  King,  on  incomplete  geological 
evidence,  is  the  close  of  the  Eocene  ;  but  this  seems  inadmissibly 
early  in  view  of  the  sharpness  of  the  Wahsatch  peaks  and  spurs 
and  of  the  enormous  amount  of  erosion  accomplished  in  the  pla- 
teau province  in  post-Eocene  time. 

It  should  be  noted,  however,  that  certain  transverse  streams 
in  the  Provo  district  have  valleys  that  are  more  maturely  opened 
than  the  canons  just  considered.  The  so-called  canons  of  Provo 
river,  Hobble  creek,  and  Spanish  fork  are  all  relatively  open,  with 
moderately  steep  and  frequently  graded  side  slopes.  This  seemed 
to  me  in  part  due  to  the  occurrence  of  weaker  rocks  where  the 
transverse  streams  have  cut  down  their  valleys,  but  I  am  not 
sure  that  this  explanation  applies  in  all  cases.  It  may  be  that  in 
some  examples  the  more  open  valleys  are  connected  with  differ- 
ences in  the  date,  amount,  and  rate  of  faulting.  Some  of  the 
transverse  valleys  are  nevertheless  of  true  canon-like  form  ;  such 
is  Weber  canon,  which  is  followed  from  the  east  by  the  Union 
Pacific  Railroad  into  the  Great  Basin  at  Ogden ;  and  also  Ogden 
canon,  a  few  miles  farther  north,  if  the  maps  may  be  trusted. 

The  part  of  the  Wahsatch  range  next  north  of  Spanish  fork 
canon,  here  called  the  Spanish  Wahsatch,  is  beautifully  carved 
with  sharp  ravines  which  preserve  their  narrow  floor  and  steep 
walls  directly  to  the  mountain  base.  Two  of  these  ravines  were 
visited.  The  beds  of  their  wet-weather  streams  pitch  forward 
at  an  angle  of  from  22°  to  34°,  steepening  near  their  mouth; 
the  slope  of  the  side  walls  is  30°.  All  the  ravines  open  close  to 
the  level  of  the  Bonneville  beach  instead  of  being  cut  down 
nearer  to  the  level  of  the  piedmont  plain ;  as  in  the  Provo 


744  PHYSIOGRAPHIC  ESSAYS 

Wahsatch,  this  peculiar  relation  should  be  here  also,  at  least  in 
part,  ascribed  to  the  recent  up-faulting  of  the  mountain  block. 

The  Wahsatch  range  has  many  other  canons  and  ravines  of 
similar  form,  so  far  as  observation  from  the  plain  in  front  of 
the  mountains  can  determine,  and  so  far  as  description  by  local 
observers  testifies. 

The  southwestern  slope  of  the  Santa  Rosa  range  north  of  Cane 
spring  deserves  further  statement.  I  had  time  to  examine  its 
general  features  from  a  spur  next  south  of  Cane  spring.  The 
strike  of  various  ledges  outcropping  on  the  bare  mountain  flanks 
was  in  general  northeastward  ;  that  is,  about  at  right  angles 
to  the  trend  of  this  part  of  the  mountain  base.  The  dip  of  the 
ledges  was  steep  southeast,  or  nearly  vertical.  Rock  structure 
was,  however,  very  faintly  exhibited  as  a  rule ;  the  mountain 
mass  is  for  the  most  part  worn  to  the  stage  of  smoothly 
graded  summits  and  spurs,  whose  graceful  forms  were  beau- 
tifully brought  out  in  late  afternoon  light.  The  spurs  terminate 
in  strong  slopes,  sometimes  maintaining  convex  longitudinal 
profiles  almost  to  their  base.  The  valleys  and  ravines  are  steep- 
walled  and  narrow-floored  to  their  very  mouths.  The  mountain 
base  is  of  long  and  gentle  curvature,  here  convex  to  the  south- 
west. Faint  scarps  in  the  washed  gravels  close  to  the  mountain 
base  were  seen  at  several  points,  and  were  noted  as  indicating 
modern  faulting.  The  gravel  wash  extends  far  forward  on  an 
even  slope,  thus  suggesting  a  vigorous  discharge  of  waste  from 
the  mountain  valleys.  For  several  miles  east  of  Cane  spring  the 
strong  wash  from  the  mountains  on  the  north  meets  a  much 
weaker  wash  from  a  series  of  low  spurs  on  the  south  ;  these  spurs 
descend  gently,  some  reaching  farther  forward  than  others,  and 
all  blending  by  gradual  concave  slopes  with  the  inclined  gravel 
plain  before  them.  So  distinct  a  contrast  between  the  forms  of 
the  mountains  on  the  north  and  those  of  the  spurs  on  the  south 
must  have  a  meaning.  No  meaning  seems  so  probable  as  that 
which  associates  the  mountain  with  strong  block  faulting  and 
active  carving,  both  continued  into  recent  time,  and  the  spurs 
with  a  long  period  of  undisturbed  erosion. 

As  a  characteristic  of  this  arid  and  thinly  settled  region,  note 
may  be  made  of  the  fruit  ranch  of  a  Basque  settler  at  the  mouth 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN 


745 


of  one  of  the  valleys  in  the  Santa  Rosa  mountains.  The  small 
stream  from  the  valleys  supplies  water  enough  to  irrigate  an 
orchard  of  a  thousand  apple  trees  and  some  alfalfa  fields ;  the 
alfalfa  serves  for  local  needs ;  the  fruit  is  sold  to  neighboring 
ranches  and  villages.  Another  valley  supplies  water  for  some 
alfalfa  fields  belonging  to  the  ranch  at  Cane  spring.  This  spring 
itself  seems  to  rise  where  the  long  wash  slope  from  the  moun- 
tains on  the  north  comes  against  the  rock  that  descends  from 
the  spurs  on  the  south.  Every  drop  of  water  available  in  the 
growing  season  is  used.  Storage  reservoirs  in  the  mountains 
would  increase  the  summer  supply,  but  such  reservoirs  would  be 
so  soon  filled  with  waste  —  should  they  indeed  escape  destruc- 
tion by  a  cloud-burst  torrent  —  that  the  cost  of  their  construc- 
tion would,  it  is  to  be  feared,  never  be  repaid. 

The  Mountain  Face.  The  study  of  mountain  morphology  is  so 
little  advanced  that  one  encounters  difficulty  both  as  to  method 
and  terms  in  attempting  to  present  a  definite  account  of  moun- 
tain forms.  It  is  evident,  however,  that  the  face  of  a  range, 
carved  on  the  fault  scarp  of  its  tilted  or  lifted  block,  should  pre- 
sent certain  features  characteristic  of  such  an  origin,  and  that 
these  features  should  be  deduced  as  carefully  as  any  others  in 
the  mental  construction  of  the  type  example,  so  that  their  occur- 
rence or  absence  in  actual  ranges  may  be  determined.  In  no 
other  way  can  it  be  ascertained  whether  the  face  of  the  range  as 
well  as  its  base  and  its  canons  testify 
in  favor  of  block  faulting.  The  follow- 
ing paragraphs  therefore  attempt  to 
discover  the  forms  that  should  char- 
acterize the  ideal  case  of  a  faulted 
block  of  homogeneous  structure 
whose  faulting  has  progressed  at  a 
slow  and  relatively  uniform  rate,  so 
that  the  sides  of  the  ravines  that 
are  eroded  in  it  shall  be  weathered 
back  to  graded  slopes  about  as  fast 
as  the  fault  block  is  raised.  Three 
significant  stages  of  faulting  and  erosion  may  be  considered.  In 
an  early  stage  (Fig.  1 18)  the  low  fault  scarp  is  notched  by  ravines 


FIG.  118.  NOTCHES  IN  THE  FRONT 
OF  A  YOUNG  TILTED  BLOCK 

Some  of  the  front  edge  of  the  block 
still  remains 


746 


PHYSIOGRAPHIC  ESSAYS 


whose  location  and  length  are  determined  by  the  site  of  pre- 
faulting  inequalities  in  the  upper  surface  of  the  block.   Adjacent 

ravines  have  not  yet  widened 
sufficiently  to  consume  the 
edge  at  the  top  of  the  block 
between  them.  In  a  later  stage 
(Fig.  119)  the  block  is  raised 
higher,  the  ravines  are  worn 
deeper  and  farther  back,  some 
of  them  being  larger  than 
others.  Nothing  of  the  upper 
front  edge  of  the  block  now 
remains,  for  the  flaring  walls  of 

FIG.  119.  NOTCHES  IN  THE  FRONT  OF  A  the  ravines  now  meet  in  a  sharP 

YOUNG  TILTED  BLOCK,  MORE  UP-       ridge  crest  that  rises  backward 

LIFTED  THAN  IN  FIG.  n8  from  the  vertex  of  a  triangular 

Nothing  of  front  edge  remains  f acet  Qn  the  block  f ront)  toward 

the  top  of  the  block.  In  the  third  stage  (Fig.  120)  the  block  is 
raised  still  higher,  and  the  ravines  have  become  still  longer  and 
deeper ;  at  this  stage  the  mountain  crest  might  become  serrate, 
and  its  back  slope  would  be  well 
dissected.  The  long,  sharp-crested 
ridges  between  the  larger  front 
ravines  are  still  terminated  by 
triangular  facets,  very  systematic 
in  form  and  position,  with  their 
bases  aligned  along  the  mountain 
front.  The  spur  sides  and  the 
facets  themselves  will  have  suf- 
fered some  carving,  as  is  shown 
in  Fig.  121,  where  some  of  the 
terminal  facets  are  enlarged.  The 
moderate  dissection  of  the  large 
facet  by-  small  ravines  results  in 
the  development  of  several  little 
basal  facets  along  the  fault  line, 
where  they  form  the  truncating  terminals  of  several  little  spurs. 
These  basal  facets  are  of  importance  in  this  stage  of  dissection, 


FIG.  120.  SPURS  AND  DEEP  RAVINES 

IN  THE  FRONT  OF  A  TILTED 

BLOCK,  MUCH  UPLIFTED 

Upper  surface  not  shown 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        747 


for    they    have    suffered   the   least   change   of  any  part  of  the 
mountain  front. 

We  are  thus  led  to  conclude  that  the  features  of  special  sig- 
nificance as  the  necessary  result  of  long-continued  faulting, 
persistent  into  the  recent 
period,  are,  first,  the  sharp- 
cut,  narrow-floored  valleys 
which  have  already  been 
considered  ;  and  secondly, 
the  large  and  small  ter- 
minal facets  of  the  spurs, 
whose  bases  show  a  nota- 
ble alignment  all  along  the 
mountain  front. 

If  faulting  be  supposed  to 
cease  after  the  stage  of  Fig.    FlG  I2I    DISSECTED  TERMINAL  FACETS  OF 
1 20  is  reached,  the  valleys  MAIN  SPURS 

will    widen    without     much    Showing  small  basal  facets  between  short  ravines; 

deepening  at  their  mouths,        drawn  on  a  larger  scale  than  Figs" II8-120 
the  spurs  will  be  narrowed,  and  the  truncating  terminal  facets  will 
in  time  be  so  far  consumed  that  the  spurs  will  become  pointed,  as 

inFig.  122.  The  further  ero- 
sion progresses  into  matur- 
ity, the  farther  will  the  points 
of  the  wasting  spurs  with- 
draw from  the  fault  line, 
and  the  more  perfect  will 
be  the  relation  of  structure 
and  form  ;  but  as  old  age  is 
reached  this  relation  is  more 
and  more  suppressed.  It  is 

FIG.  1 22.   TAPERING  SPURS  BETWEEN  OPEN   evident  that  late  maturity  or 
VALLEYS  early  old  age  will  introduce 

Late-mature  stage  of  a  tilted  block ;  same  scale        the    System   of   interlocking 

valleys  and    spurs  already 
described  as  characteristic  of  subdued  residual  mountains. 

Spurs  and  Terminal  Facets  of  the  Wahsatch  Range.    The  Span- 
ish Wahsatch,  opposite  the  villages  of  Springville  and  Mapleton, 


748 


PHYSIOGRAPHIC  ESSAYS 


presents  a  group  of  forms  that  resembles  to  a  singular  degree 
those  represented  in  Figs.  120  and  121.  The  mountain  base  is 
characterized  by  a  series  of  basal  spur  facets,  sloping  at  an 
angle  of  38°  or  40°,  and  possessing  remarkably  systematic  forms 
which  correspond  closely  to  those  deduced  for  the  ideal  type  in 
its  maturely  dissected  stage.  The  ridge  or  crest  line  of  the 
spurs  slopes  at  angles  that  do  not  vary  greatly  from  25°.  Fig. 
123,  enlarged  from  photograph  and  sketch,  presents  a  detailed 
view  of  this  part  of  the  Wahsatch,  in  which  the  sharp-crested 
ridges,  with  their  peculiarly  systematic  terminal  facets,  rise  be- 
tween the  sharp-cut  ravines  of  the  mountain  front.  The  differ- 
ence between  these  beautifully  sculptured  forms  and  the  more 
rigid  diagrammatic  features  of  Figs.  1 18—122,  is  not  a  difference 

of  kind,  for  every 
element  in  the  ideal 
view  is  matchable 
with  a  correspond- 
ing element  in  the 
actual  view ;  it  is 
rather  a  difference 
due  to  the  occur- 
rence in  nature  of 
innumerable  little 
irregularities,  the 
result  of  slight  variations  of  rock  mass  and  of  sculpturing  proc- 
ess, whereby  actual  mountains  depart  in  so  pleasing  and  graceful 
a  manner  from  the  hard  and  conventional  lines  of  diagrams.  In 
spite  of  these  differences,  the  notable  characteristic  of  this  part 
of  the  Wahsatch  front  is  its  model-like  form,  every  element  of 
which  is  so  systematically  arranged  that  it  can  be  understood ; 
and  thereon  depends  much  of  its  attractiveness.  The  expression 
of  its  features  is  open  and  frank,  without  that  complication  of 
unresolvable  elements  which  makes  the  meaning  of  larger  moun- 
tain forms  so  difficult  of  full  understanding.  One  reason  for  the 
simplicity  of  form  here  exhibited  is  the  simplicity  of  rock  struc- 
ture in  the  mountain  block.  The  strata  of  which  it  is  built  lie 
nearly  horizontal  in  the  district  that  we  examined,  and  none  of 
them  are  sufficiently  unlike  their  neighbors  in  strength  or 


FIG.  123.   RAVINES,  SPURS,  AND  TERMINAL  FACETS 

OF  THE  SPANISH  WAHSATCH 
Looking  east ;  drawn  from  sketch  and  photograph 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        749 

weakness  to  determine  the  occurrence  of  strong  cliffs  or  benches. 
There  are  indeed  several  delicately  embossed  contouring  lines  on 
the  spur  slopes  by  which  the  structure  of  the  mass  is  indicated 
in  the  distant  view ;  and  on  climbing  the  slopes  there  are  abun- 
dant small  outcrops  by  which  the  inference  from  the  distant  view 
is  confirmed ;  but  as  a  whole  the  slopes  are  graded  and  cloaked 
with  a  thin  cover  of  creeping  waste,  so  that  the  observer's  atten- 
tion is  not  too  soon  diverted  from  the  study  of  mountain  sculp- 
ture by  an  emphatic  exhibition  of  mountain  structure. 

I  first  saw  the  spurs,  facets,  and  ravines  of  this  mountain  front 
from  the  passing  excursion  train  of  the  International  Geological 
Congress  in  1891,  but  they  were  then  only  regarded  as  "  pecul- 
iar." They  were  seen  a  second  time  on  returning  from  a  Colo- 
rado canon  excursion  in  1900,  and  on  that  occasion,  although  they 
were  then  again  observed  only  from  passing  trains  northward  on 
one  road  in  the  morning,  and  southward  on  another  in  the  after- 
noon, the  possibility  and  necessity  of  explaining  them  as  a  result 
of  erosion  on  a  faulted  block  was  recognized.  During  the  sum- 
mer of  1902  my  party  made  a  special  visit  to  these  significant 
spurs,  walked  along  their  base  for  a  short  distance,  ascended  the 
slope  of  one  of  the  facets,  and  came  down  again  by  the  ravine 
alongside  of  it.  There  seemed  to  be  no  escape  from  the  conclu- 
sion that  extensive  and  recent  faulting  of  the  mountain  block  is 
here  indicated,  not  only  by  the  complete  absence  of  the  mountain 
rocks  west  of  the  almost  rectilinear  base-line,  as  already  set  forth, 
but  also  by  the  detail  of  form  on  the  mountain  face,  and  particu- 
larly by  the  well-defined  facets  in  which  the  spurs  terminate. 

The  late  afternoon  view  of  the  Wahsatch  range  from  the  shore 
of  Utah  lake  brings  the  mountain  forms  clearly  forth.  The  eye, 
after  wandering  along  other  less  intelligible  parts  of  the  range, 
turns  repeatedly  to  the  block  north  of  Spanish  fork  canon  with 
enjoyment  of  the  fuller  meaning  found  there.  Elsewhere  one's 
curiosity  is  excited  ;  there  it  is  satisfied.  After  the  sharply  defined 
terminal  facets  of  the  mountain  spurs  are  found  to  be  systematic 
elements  of  form  in  the  Spanisn  Wahsatch,  they  may  be  recog- 
nized in  many  other  parts  of  the  range,  but  nowhere,  so  far  as  I 
have  seen,  with  the  model-like  distinctness  of  development  that 
is  exhibited  in  the  example  just  described. 


750  PHYSIOGRAPHIC  ESSAYS 

When  the  Wahsatch,  near  Provo,  is  seen  from  a  point  not  too 
near  its  base,  several  spur  facets  may  be  distinguished  between 
the  canons  and  ravines  by  which  the  mountain  front  is  scored  ; 
but  the  edges  of  the  facets  are  dull,  like  the  edges  of  a  crystal 
of  apatite.  In  the  Spanish  block  the  sharp-edged  facets  tempt 
one  to  sketch  in  outline  ;  in  the  Provo  block  it  is  by  no  means  so 
easy  to  do  justice  to  the  mountain  form  in  an  unshaded  drawing. 
One  reason  for  this  is  that  the  ravines  here  are  not  very  deeply 
carved  —  except  the  larger  ones,  called  canons,  whose  streams 
head  in  subsequent  valleys  back  of  the  frontal  ridge  —  and  hence 
the  spurs  do  not  stand  forth  between  the  ravines  in  strong  relief. 
Moreover,  accompanying  and  perhaps  causing  this  loss  of  defi- 
nition in  the  spurs  and  facets,  there  is  an  increased  variety  of 
texture  in  the  rock  mass,  whereby  certain  resistant  strata  stand 
forth  bare  and  prominent  between  weaker  neighbors ;  the  atten- 
tion is  thus  involuntarily  somewhat  distracted  from  sculpture  and 
turned  toward  structure.  The  facets  are  nevertheless  undeniably 
present,  and  in  essentially  the  same  relation  to  spur  and  base-line 
as  is  shown  in  the  type  diagram  (Fig.  120).  The  southern  end  of 
the  Provo  block  possesses  the  most  distinct  examples,  some  of 
which  will  be  described  in  the  following  section. 

The  Wahsatch  spurs  that  descend  near  Little  Cottonwood  canon, 
between  Provo  and  Salt  Lake,  are  systematically  terminated  by 
clearly  recognizable  facets. 

The  Ogden  Wahsatch  also  offers  illustrations  of  the  systematic 
faceting  of  its  spurs,  those  adjoining  Weber  canon  being  the  most 
distinct.  Farther  north,  back  of  the  city  of  Ogden,  the  facets  are 
round-edged,  yet  distinctly  recognizable  as  systematic  elements 
of  form,  like  those  of  the  Provo  Wahsatch. 

The  spurs  of  several  other  ranges,  seen  from  train  and  stage 
in  Utah  and  Nevada,  were  terminated  by  facets  of  more  or  less 
distinct  form.  The  spurs  of  the  Santa  Rosa  range  were  more 
rounded  than  many  of  the  others,  and  the  terminal  facets  were 
indistinct.  The  eastern  face  of  Pine  Forest  mountains  in  northern 
Nevada  is  notably  steep  and  scarp-like,  descending  to  a  relatively 
rectilinear  base.  The  scarp  is  sharply  cut  by  narrow  valleys  which 
remain  narrow  to  their  very  mouths.  Some  of  the  spurs  end  in 
rounded  facets.  Signs  of  recent  faults  in  the  gravels  at  the 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        751 

mountain  base  were  noted,  but  at  too  great  a  distance  for  me  to 
feel  certain  of  their  meaning.  The  height  of  the  range  gradually 
decreases  to  its  trailing  southern  end.  In  this  range  more  clearly 
than  elsewhere  the  narrow  valleys  seemed  to  be  cut  beneath 
a  rolling  upland  of  earlier  origin. 

The  Spur  Facets  are  not  Wave-Cut.  The  terminal  facets  of 
the  Wahsatch  front  rise  over  the  Bonneville  beaches  in  such  a 
way  as  to  suggest  a  possible  origin  as  wave-cut  cliffs.  It  is  not 
to  be  doubted  that  waves  could,  if  time  be  allowed,  cut  off  the 
points  of  spurs  so  as  to  truncate  them  in  triangular  facets,  but  in 
that  case  the  facets  should  be  associated  with  certain  other  fea- 
tures which  are  significantly  absent  from  the  Wahsatch  range. 
This  may,  as  usual,  be  best 
demonstrated  by  considera- 
tion of  the  progress  of  wave 
work  in  an  ideal  case. 

If  the  surface  of  a  sea  or 
lake  should  rise  on  a  ravined 
mountain  front,  so  as  to  gain 
an  irregular  shore-line,  ABCD 
(Fig.  124),  the  promontories 
might  in  time  be  cut  back  to  FlG' I24'  SpURS  CUT  BY  WAVES 

,,  .    ,  ,       i  ,.  .     ABCD.  initial  shore-line  at   time  of  submerg- 

the  straight  shore-line,  DFH,    ence.  DKF,  cliff  facet  cut  back  in  spur  DEF. 

Over  Which  the  Spurs  WOUld  FGH,  spur  platform  fronting  its  cliff  facet  FLH, 
.,  •  ...  after  withdrawal  of  lake  waters 

then  terminate  m  triangular 

cliff  facets,  DKF,  FLH.  But  in  such  a  case  the  valleys  should  not 
remain  narrow-mouthed  during  the  progress  of  the  wave  work, 
but  should  widen  somewhat  and  allow  the  streams  to  develop 
flood  plains  on  which  they  could  wander  a  little  ;  and  after  the 
lake  waters  had  disappeared,  the  facets  should  look  out  upon 
triangular  rock  platforms,  FGH,  systematically  related  in  form 
and  area  to  the  facets.  As  a  matter  of  fact,  the  triangular  rock 
platforms  and  the  widened  valley  mouths  are  wanting  in  every 
case  that  came  under  my  notice.  It  cannot  be  supposed  that  the 
mountain  front  was  cut  back  by  waves  at  so  low  a  level  that  the 
wave-cut  platform  is  now  concealed  by  mountain  waste ;  for  in 
that  case  the  narrow  ravines  should  also  have  been  cut  down  to 
the  same  low  level,  instead  of  opening,  as  they  so  often  do, 


752  PHYSIOGRAPHIC   ESSAYS 

rock-floored  on  the  mountain  flank,  and  allowing  the  streams 
to  continue  their  descent  on  gravel  fans  that  rise  at  the  apex 
distinctly  above  the  intermont  plain.  One  of  the  best  localities 
for  the  illustration  of  these  features  is  at  the  southern  end  of 
the  Provo  Wahsatch,  northeast  of  Springville,  where  the  base- 
line curves  from  south  to  southeast.  Several  ravines  furrow  the 
mountain  face,  dividing  it  into  a  number  of  sub-parallel  spurs, 
all  of  which  are  cut  off  by  rather  well-defined  triangular  facets. 
If  these  facets  are  explained  as  shore-line  cliffs,  rock  platforms 
should  stretch  from  a  quarter  to  a  half  mile  forward  from  the 
cliff  base  into  the  plain  ;  but  no  such  platforms  are  to  be  seen. 
If  any  rock  platform  exists,  it  must  be  supposed  that  it  was  cut 
at  a  much  lower  level  than  that  of  the  Bonneville  shore-line,  and 
that  it  is  buried  under  the  sands  and  clays  that  cover  the  low 
ground  ;  but  the  existence  of  a  wave-cut  platform  at  such  a  depth 
is  inconsistent  with  the  opening  of  the  ravines  in  the  mountain 
flank  several  hundred  feet  above  the  plain  ;  the  ravines  would 
necessarily  have  been  deepened  by  their  streams  as  the  cliffs  and 
platforms  were  cut  back  by  the  waves ;  hence  the  supposition  of 
a  wave-cut  origin  for  the  facets  cannot  be  favorably  entertained ; 
an  origin  by  faulting  is  much  more  reasonable.  It  is  noticeable 
that  the  stream  lines  in  this  part  of  the  Wahsatch  pitch  with  in- 
creasing steepness  in  the  narrow,  gorge-like  mouths  of  the  ravines, 
thus  hurrying  between  a  gentler  but  still  steep  descent  down  the 
ravines  in  the  mountain  flank  above,  and  a  gentler  descent  through 
the  Bonneville  gravels  on  the  way  to  the  plain  below.  Indeed, 
the  gorge -like  mouths  of  the  ravines  seems  to  be  incised  some- 
what below  the  base  of  a  series  of  simply  triangular  facets,  so  as 
to  give  the  spur  sections  the  beginning  of  a  house-end  pattern, 
as  if  the  faulting  of  the  mountain  block  had  been  locally  acceler- 
ated not  long  ago.  The  features  of  this  interesting  locality  would 
well  repay  a  detailed  study. 

True  wave-cut  cliffs  and  their  correlated  rock  platforms  may, 
as  is  well  known,  be  seen  at  various  points  on  the  Bonneville 
shore-line,  but  the  cliffs  are  usually  of  much  less  height  than 
that  of  the  spur  facets  in  the  Wahsatch  front ;  and  in  no  case 
had  the  rock  platforms  that  I  saw  nearly  so  great  a  breadth  as 
would  be  demanded  by  the  forward  prolongation  of  the  faceted 


MOUNTAIN   RANGES  OF  THE  GREAT  BASIN        753 

Wahsatch  spurs,  so  that  the  slope  of  the  spur  crest  line  should 
descend  to  the  platform  level.  The  facets  of  the  Spanish  Wah- 
satch front  the  basin  of  Utah  lake,  not  over  twenty-five  miles 
broad  from  east  to  west :  the  Bonneville  waters  here  must  have 
been  much  less  powerful  than  in  their  more  open  areas  farther 
north  ;  yet  these  facets  are  much  larger  than  the  true  wave-cut 
cliffs  that  are  seen  on  more  exposed  parts  of  the  old  shore-line. 
The  best  facets  of  the  Ogden  Wahsatch,  above  mentioned  as 
lying  close  to  Weber  canon,  cannot  have  been  much  affected 
by  the  Bonneville  waves,  for  during  much  of  Bonneville  time  this 
part  of  the  mountain  base  was  well  protected  by  the  growing 
delta  of  Weber  river. 

The  Erosion  of  the  Spur  Facets.  It  is  evident  from  what  has 
been  said  in  the  section  on  the  mountain  face  that  the  retreat 
of  a  mountain  front  from  its  initial  fault  scarp  will  be  greater 
on  the  stream  lines  than  on  the  interstream  surfaces,  and  again 
greater  at  the  apex  of  a  facet  than  at  its  base.  The  concentration 
of  drainage  —  even  if  it  be  only  wet-weather-  drainage  —  along 
the  stream  line  of  the  ravines,  and  the  increase  in  the  volume  of 
the  streams  from  head  to  mouth  has  given  them  strength  enough 
to  remove  the  waste  that  weathers  and  creeps  down  from  the 
ravine  walls.  There  is,  however,  at  present  no  such  concentra- 
tion of  removing  agencies  along  the  foot  of  the  mountains ;  and 
as  the  duration  of  the  Bonneville  waters  at  their  various  levels 
has  been  but  a  small  fraction  of  the  whole  life  of  the  mountains, 
it  may  be  said  that  there  has 
prevailingly  been  no  active  agent 


,W 

• ^^'W-w///;${\w/ •' '  /i/jmiiniM  m  i  til  i  > 

the  mouths  of  the  streams. 

If  the  fault  plane  were  verti- 
cal, a  large  amount  of  rock  waste 
would  have  fallen  from  it,  and 
in  the  absence  of  any  effective 
removing  agency  along  the  moun- 
tain base,  some  of  the  waste  should  accumulate  there  as  a  talus 
(Fig.  125),  whose  foot  should  advance  in  front  of  the  fault  line. 
The  conspicuous  absence  of  such  talus  makes  it  probable  that 


754  PHYSIOGRAPHIC  ESSAYS 

the  fault  plane  was  by  no  means  vertical,  and  suggests  that  the 
slope  of  the  spur  facets  may  not  be  greatly  unlike  the  slope  of 
the  faults.  In  the  Spanish  Wahsatch  the  small  facets  slope  at 
an  angle  of  38°  or  40°  ;  in  the  Provo  Wahsatch  the  slope  is 
from  32°  to  38°.  Certain  ranges  in  northern  Nevada  had  simi- 
larly steep  basal  slopes. 

Other  Parts  of  Block. Mountains.  In  the  early  stages  of  fault- 
ing the  back  slope  of  a  tilted  mountain  block  should  exhibit  its 
pre -faulting  form  little  changed,  except  that  all  the  slopes  and 
streams  which  had  been  steepened  by  the  tilting  would  show 
signs  of  more  active  erosion  than  the  other  parts.  The  lower  part 
of  the  back  slope  would  be  buried  under  accumulating  waste. 

In  a  later  stage  of  faulting  it  might  be  impossible  to  recognize 
any  survivors  of  the  pre-faulting  forms,  unless  near  the  back  base 
where  the  small  depth  to  which  erosion  could  penetrate  would 
delay  change.  The  back  base-line  would  expectably  be  much 
more  sinuous  than  the  front  base-line,  for  at  the  back  of  the 
range  the  gravels  and  sands  of  the  intermont  depression  would 
mount  obliquely  upon  a  surface  in  which  the  inequalities  of  pre- 
faulting  time  had  been  somewhat  exaggerated  by  the  revived 
erosion  of  the  early  stages  of  tilting. 

In  the  early  and  later  stages  of  faulting  both  faces  of  a  lifted 
mountain  block  would  present  features  similar  to  those  already 
described  as  occurring  on  the  faulted  face  of  a  tilted  block,  while 
the  upper  surface  of  the  lifted  block  would  exhibit  features 
dependent  on  revived  erosion,  such  as  are  commonly  found  in 
uplifted  regions.  In  young  blocks  of  this  kind  the  intensity  of 
revived  erosion  would  rapidly  increase  toward  the  block  border  ; 
in  this  respect  the  upland  of  a  young  block  would  present  fea- 
tures very  similar  to  those  found  in  the  Arizona  plateaus  that 
border  on  the  Colorado  canon,  or  in  the  plateaus  of  western 
Germany  which  border  either  on  the  Rhine  gorge  below  Bingen 
or  the  Rhine  graben  above  Bingen ;  for  so  far  as  the  dissection 
of  an  upland  is  concerned,  it  matters  little  whether  its  streams 
descend  by  a  fault  scarp  to  a  lowland  or  by  a  canon  wall  to 
a  river. 

In  older  uplifted  blocks  of  longer  continued  faulting,  the  con- 
trast of  scarp  and  upland  woulcj  be  weakened  ;  and  after  the 


MOUNTAIN   RANGES  OF  THE  GREAT  BASIN        755 

faulting  was  far  advanced,  the  contrast  would  disappear  entirely. 
The  battered  retreat  of  both  scarps,  gnawed  by  retrogressive 
ravines,  would  result  in  transforming  the  upland  into  a  more 
or  less  serrated  ridge. 

Many  special  conditions  might  be  imposed  upon  these  general 
deductions  by  assuming  particular  features  of  pre-faulting  relief 
and  drainage.  These  conditions  need  not  be  entered  upon  here, 
because  my  observations  did  not  go  far  enough  to  provide  a  large 
variety  of  facts  with  which  deductions  of  specialized  types  could 
be  confronted.  It  may  be  noted,  however,  that  the  deduced  fea- 
tures of  the  back  slope  of  a  tilted  block  are  not  so  much  unlike 
the  forms  of  residual  mountains  as  are  those  of  the  front  of  such 
a  block.  It  is,  therefore,  not  to  be  expected  that  tilted-block 
ranges  can  be  recognized  so  well  when  their  back  is  seen  as 
when  one  looks  at  their  expressive  face.  But  when  the  features 
characteristic  of  the  back  slope  of  a  tilted  block  occur  on  one 
side  of  a  range,  while  those  appropriate  to  the  faulted  face  occur 
on  the  other  side,  it  is  reasonable  to  look  upon  such  a  range  as 
the  result  of  block  faulting. 

The  eastern  side  of  the  Santa  Rosa  mountains  north  of  Win- 
nemucca,  Nevada,  for  example,  does  not  imitate  the  well-defined 
base-line  of  the  western  side,  so  far  as  I  saw  this  range.  The 
eastern  valleys  are  open  and  well  graded  between  spaced  spurs. 
The  same  is  true  of  the  eastern  base  of  Jackson  range,  whose 
western  base  has  already  been  mentioned  as  suggestive  of  fault- 
ing. Moreover,  in  profile  this  range  resembles  a  tilted  block 
when  seen  from  the  north  in  such  a  way  that  its  ravines  are 
hidden  behind  its  spurs.  The  crest  line  is  near  the  western 
side  where  the  slopes  are  precipitous,  while  the  eastern  slopes 
are  much  more  gradual. 

If  any  ranges  have  been  carved  from  uplifted  blocks,  bounded 
by  faults  on  both  sides,  they  have  —  so  far  as  the  examples  that 
I  saw  are  concerned  —  reached  the  advanced  stage  of  dissection 
in  which  the  initial  upland  is  carved  into  a  serrate  ridge.  My 
line  of  travel  seldom  made  it  possible  to  see  both  sides  of  a  single 
range,  and  hence  my  notes  leave  it  uncertain  in  most  cases 
whether  or  not  a  range  with  a  well-defined  base-line  on  one  side 
is  similarly  formed  on  the  other  side. 


756  PHYSIOGRAPHIC  ESSAYS 

Modern  Fatilting.  It  is  certainly  very  significant  that  indisput- 
able evidence  of  modern  displacement  should  be  found  close  along 
certain  mountain  base-lines  where  abundant  evidence  of  long- 
continued  earlier  faulting  is  provided  by  the  mountain  form.  This 
has  been  so  clearly  pointed  out  by  Gilbert  and  Russell  that  little 
space  need  be  given  to  it  here.  Suffice  it  to  say,  that  repeated 
instances  of  scarps  in  gravel  deltas  and  fans  were  noted  last 
summer  along  the  Wahsatch  base,  as  well  as  along  the  border 
of.  certain  other  ranges  to  be  described  below.  A  distinct  scarp 
in  the  gravels  of  the  Bonneville  beach  is  traceable  all  along 
the  front  of  the  Spanish  Wahsatch,  a  little  forward  from  the 
base  of  the  facets.  The  breaks  in  the  delta  of  Rock  canon 
creek  and  in  various  other  gravel  deposits  near  Provo  were 
easily  recognized. 

It  is  sometimes  suggested  that  the  displacements  in  the 
Bonneville  gravels  are  more  of  the  nature  of  superficial  land- 
slides than  of  deep-seated  faults.  Taken  alone  they  might  per- 
haps be  so  considered,  but  taken  in  connection  with  all  the 
associated  features,  they  cannot  be  regarded  as  independent 
of  displacement  in  the  underlying  rock  mass. 

There  is,  however,  one  aspect  of  the  modern  faulting  that  de- 
serves consideration.  In  all  cases  that  I  have  seen,  the  modern 
movements  are  so  placed  that  they  must  be  taken  as  the  con- 
tinuation of  long-maintained  displacements  whose  total  measure 
must,  as  a  rule,  amount  to  many  hundreds  or  some  thousands 
of  feet.  No  other  explanation  has  been  found  for  the  presence 
of  such  mountain  masses  as  have  been  described  above,  standing 
in  strong  relief  on  one  side  of  the  base-line,  while  there  are  only 
gravels  and  sands  to  be  seen  on  the  other  side.  It  is,  of  course, 
conceivable  that  modern  faulting  may  have  been  here  and  there 
begun  on  new  lines,  essentially  independent  of  the  older  fault 
lines,  but  such  cases  must  be  rare ;  for  it  is  to  be  expected  that 
if  a  modern  fault  occurs  on  a  new  line,  it  should  run  across 
country  indifferent  to  preexistent  structures.  Such  a  fault 
might  run  obliquely  across  an  intermont  plain,  then  traverse  a 
mountain  range,  and  continue  into  another  plain  beyond  the 
range,  the  whole  length  of  the  fault  being  marked  by  a  scarp  of 
more  or  less  distinct  form.  The  Great  Basin  has  not  yet  been 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        757 

carefully  enough  explored  to  prove  that  no  such  faults  occur ; 
but  the  region  is  well  enough  known  to  warrant  the  provisional 
statement  that  new  faults  of  a  date  as  recent  as  the  scarps 
of  the  Bonneville  deposits  are  rare,  except  in  connection  with 
old  faults. 

On  the  other  hand,  there  seem  to  be  many  ancient  faults  in 
the  Basin  ranges  on  which  movement  ceased  long  ago.  This  is 
shown  by  the  obliteration  through  erosion  of  the  relief  due  to 
faulting ;  or  sometimes  by  so  great  an  excess  of  erosion  in  the 
uplifted  block  over  that  in  the  thrown  block  that  the  thrown 
block  now  stands  above  the  lifted  block,  the  fault  scarp  being 
thus  topographically  reversed  by  erosion.  Many  examples  of 
these  kinds  are  given  by  Spurr.  It  does  not,  however,  seem 
admissible  to  argue  from  the  absence  of  modern  movement  on 
these  faults,  or  from  the  apparent  absence  of  modern  faults 
within  the  ranges,  that  no  long-maintained  faulting  can  have 
taken  place  along  the  range  borders.  That  must  be  determined 
by  evidence  furnished  by  the  borders  of  the  ranges  themselves. 

The  Measure  and  Distribution  of  Faulting.  It  may  be  noted 
that  only  an  incomplete  measure  of  the  total  movement  in  block 
faulting  is  determined  by  the  difference  of  altitude  between  the 
mountain  base  and  the  reconstructed  crest  in  a  lifted  or  tilted 
block  ;  for  in  addition  to  this  measure  there  must  be  a  certain 
supplement  by  which  the  inequalities  of  the  pre-faulting  surface 
have  been  depressed  out  of  sight  in  the  thrown  block.  Advanced 
old  age  in  the  pre-faulting  cycle,  and  youth  or  early  maturity  in 
the  present  cycle,  are  the  conditions  demanding  the  least  meas- 
ure of  block  faulting ;  for  the  small  relief  of  advanced  old  age  in 
the  preceding  cycle  would  be  consistent  with  the  easy  burial  of 
all  rock  surfaces  near  the  fault  line  in  the  thrown  block  ;  and 
youth  or  early  maturity  in  the  present  cycle  would  call  for  the 
least  addition  to  the  existing  height  in  reconstructing  the  crest 
of  the  mountain  block  near  the  fault-line. 

It  is  worth  while  to  call  attention  at  this  point  to  a  corollary 
that  follows  from  the  provisional  conclusion  above  stated  regard- 
ing the  prevailing  absence  of  modern  faults  except  along  the 
base-lines  of  certain  ranges  where  independent  lines  of  evidence 
lead  to  the  belief  that  the  modern  movements  are  but  the  latest 


758  PHYSIOGRAPHIC  ESSAYS 

displacements  on  faults  of  much  greater  age.  The  corollary  is 
this  :  the  total  displacement  on  these  long-lived  faults  must  be 
usually  greater  than  the  ordinary  measure  of  pre-faulting  relief 
in  the  Great  Basin  region.  For  the  fault  lines  must  have  origi- 
nally run  indifferently  to  the  structure  of  the  region,  and  there- 
fore indifferently  also  to  whatever  relief  the  region  had  assumed 
when  the  faulting  began ;  -and  yet  the  thrown  block  is  now  as 
a  rule  completely  covered  with  gravels  and  sands  washed  from 
the  heaved  block.  Exceptions  to  this  rule  are  found  at  certain 
points,  but  they  are  rare.  If  further  exploration  confirm  the 
provisional  conclusion  above  referred  to,  this  corollary  may  have 
some  value. 

In  this  connection  it  may  be  noted  that  the  great  measure  of 
displacement  inferred  by  King  for  the  Wahsatch  fault  (b,  745) 
seems  unnecessary.  If  the  folded  strata  of  the  range  had  been 
reduced  to  moderate  relief  by  pre-faulting  erosion,  —  and  this 
seems  not  improbable  if  one  may  judge  by  the  enormous  volume 
of  the  Eocene  (Vermilion  creek)  Tertiary  to  the  east  (King,  &, 
745),  — the  measure  of  the  fault  need  not  be  more  than  enough 
to  raise  the  crest  of  the  range  above  the  rock  floor  that  is  buried 
under  the  sediments  of  the  Salt  Lake  basin ;  that  is,  from  six 
thousand  to  ten  thousand  feet  instead  of  forty  thousand. 

It  was  suggested  by  Van  Hise  in  the  discussion  of  this  subject 
at  the  recent  Washington  meeting  of  the  Geological  Society  of 
America  that  the  displacement  in  faults  of  large  throw,  such  as 
those  by  which  the  Basin  ranges  have  been  formed  are  believed 
to  be,  is  usually  distributed  on  grouped  fractures  instead  of  tak- 
ing place  on  a  single  plane  of  displacement.  All  the  ranges  that 
came  under  my  observation  last  summer  are  non-committal  on 
this  point,  except  in  so  far  as  the  absence  of  discoverable  frac- 
tures in  the  front  part  of  the  mountains  requires  that  any  addi- 
tional fractures  besides  the  one  which  determines  the  mountain 
base  should  be  forward  from  it,  and  concealed  under  the  gravels 
of  the  piedmont  plain.  Certainly,  if  there  are  distributed  faults 
in  the  Spanish  Wahsatch  block,  the  displacements  on  the  minor 
faults  within  the  block  must  have  ceased  long  enough  ago  to 
have  been  obliterated,  so  far  as  surface  form  is  concerned,  in  the 
smoothly  graded  slopes  of  the  spurs ;  while  the  movement  on 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN 


759 


the  main  fault  along  the  front  margin  of  the  block  has  continued 
to  so  modern  a  date  as  still  to  have  distinct  control  over  the 
form  of  the  terminal  facets. 

An  article  of  interest  in  this  connection  has  been  published 
by  D.  W.  Johnson  on  block  mountains  in  New  Mexico,  from 
which  it  appears  that  Sandia  mountain,  near  Albuquerque,  is  a 
large  block  with  its  chief  displacement  along  the  strong  escarp- 
ment that  it  presents  to  the  west,  but  with  many  smaller  dis- 
placements within  its  mass,  thus  confirming  the  suggestion  of 
distributive  faulting  as  made  by  Van  Hise.  The  dynamics  of 
faulting  are,  however,  not  yet  so  well  understood  that  it  is  safe 
to  assert  the  occurrence  of  distributive  faulting  in  all  block 
mountains.  Surely  no  one  could  have  hesitated  to  believe  that 
the  Sandia  block  was  faulted,  even  if  minor  faults  had  not  been 
found  on  its  back  slope.  In  the  plateau  province  of  Utah  and 
Arizona  several  of  the  greater  faults  are  demonstrably  on  rela- 
tively simple  fractures ;  for  the  strata  of  the  adjoining  blocks 
come  close  to  the  fault  line  without  noticeable  disturbance ; 
there  is  room  for  fault  breccias  fifty  or  one  hundred  feet  wide, 
but  apart  from  that  the  faults  seem  to  be  for  the  most  part 
simple  and  clean  cut. 

It  is  evident  that  the  examples  of  Basin  ranges  here  described 
are  alone  too  few  in  number  to  support  any  safe  conclusion  as  to 
the  origin  of  the  Basin  ranges  in  general.  The  Wahsatch  range 
forms  the  eastern  border  of  the  Great  Basin  province,  and 
although  it  seems  to  be  of  fault-block  origin,  it  cannot  be  taken 
as  a  typical  example  of  one  of  the  isolated  ranges  within  the 
Great  Basin.  The  chief  profit  that  comes  from  the  study  of  the 
Wahsatch  range  is  the  definition  of  certain  criteria  by  which 
fault-bordered  ranges  may  be  determined  elsewhere ;  and  this 
profit  will  be  increased  when  the  back  or  eastern  slope  of  the 
Wahsatch  shall  have  been  studied  in  the  same  relation.  The 
other  ranges  above  mentioned  have,  however,  a  certain  value  in 
that  they  were  chance  samples,  not  selected  beforehand  because 
they  were  believed  to  be  faulted  blocks,  but  observed  as  they 
happened  to  be  passed  while  the  observer  was  on  his  way  to 
other  points.  They  thus  serve  to  indicate  at  least  a  probability  • 
that  other  ranges  in  the  same  region  have  a  similar  structure. 


760 


PHYSIOGRAPHIC  ESSAYS 


The  Pueblo- Stein  Moun- 
tains. By  taking  a  three-day 
dusty  stage  ride  northward 
from  Winnemucca,  Nevada, 
I  was  enabled  to  give  a  week 
to  the  study  of  the  Pueblo 
and  Stein  mountains  that 
cross  the  Nevada-Oregon 
boundary  a  little  west  of  the 
north  and  south  line  marked 
by  the  post  offices  of  Denio 
and  Andrews.  The  stage 
road  carried  me  past  the 
Santa  Rosa,  Jackson,  and 
Pine  Forest  ranges,  of  which 
some  mention  has  already 
been  made.  The  route  for 
part  of  the  distance  lay  on  the 
dead-level  gray  silt  plain  of 
the  extinct  lake  Lahontan, 
whose  successive  shore-lines 
were  traceable  at  various 
heights  on  the  inclosing 
slopes.  A  long  gravel  spit, 
hooked  to  the  east  at  various 
levels,  stretched  northward 
from  the  Jackson  range  to 
Mason's  crossing  of  Quinn 
river. 

The  general  result  of  this 
week's  work  gave  me  the 
impression  that  the  Pueblo- 
Stein  mountain  range  is 
more  eroded  than  would  be 
inferred  from  Russell's  de- 
scription of  it  (b,  439,  444) ; 
but  there  can  be  no  reasonable  doubt  that  it  represents  a  long 
fault  block.  The  following  pages  contain  a  direct  statement  of 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        761 

the  evidence  to  this  conclusion,  without  analysis  of  the  method 
by  which  the  conclusion  is  reached.  The  analysis  has  been  suf- 
ficiently stated  in  the  preceding  pages  ;  its  results  may  now  be 
employed  without  restatement  of  the  method  of  reaching  them. 
This  is  the  historical  order  in  the  development  of  methods  of 
investigation,  with  the  time  element  condensed.  When  a  geolo- 
gist nowadays  describes  vertical  strata  of  conglomerate  as  of 
sedimentary  origin,  he  does  not  again  go  over  De  Saussure's 
argument  concerning  the  conglomerate  of  Valorsine  ;  when  a 
physiographer  now  asserts  the  occurrence  of  a  subsequent  valley 
on  the  evidence  of  stream  course  and  rock  structure,  he  need 
not  repeat  the  argument  by  which  subsequent  valleys  were  first 
explained  by  Jukes  in  the  basin  of  the  Blackwater.  These  are 
settled  questions  and  may  therefore  be  treated  by  the  short 
and  direct  method  that  steps  at  once  from  observation  to  con- 


w 


\ 

\  Crystallines  \  \  X  \  \V  \ 

\      \      \        \          '     \    x     \       x      ' 


FIG.  127.   CROSS  SECTION  OF  PUEBLO  MOUNTAINS,  LOOKING  NORTH 

elusion.  So  may  the  question  of  block  mountains  be  treated 
by  the  short  method,  provided  the  complete  method  has  been 
tried  and  found  valid. 

The  Pueblo  mountains  of  southern  Oregon  (Fig.  126)  overstep 
the  state  boundary  at  Denio  and  extend  about  ten  miles  south- 
ward into  Nevada.  They  trend  northward  to  a  high  dome  fifteen 
miles  north  of  Denio,  and  then  fall  off  in  a  broad,  westward 
reentrant  back  of  Doane's  and  Field's  ranches.  The  high  ser- 
rated range  north  of  the  reentrant  is  the  beginning  of  the  Stein 
(or  Steen)  mountains.  The  Pueblo  mountains  consist  of  two 
ranges  for  most  of  their  length.  The  eastern  or  front  range 
(Fig.  127)  is  made  of  ancient  crystalline  rocks,  such  as  diabases 
and  mica  schists.  The  western  or  back  range  is  made  of  bedded 
lavas,  basaltic  so  far  as  I  saw  them,  whose  westward  dip  of  15° 
or  20°  is  well  expressed  in  a  series  of  east-facing  escarpments. 
Paired  wet-weather  subsequent  streams  drain  the  longitudinal 


762 


PHYSIOGRAPHIC   ESSAYS 


depression  between  the  two  ranges,  and  their  gathered  waters 
escape  eastward  by  deep-cut,  narrow-floored,  steep-walled  gorges 
through  the  front  range  to  the  broad  plain  known  as  Alvord 
valley.  Russell  marks  a  fault  along  the  intermediate  depression 
(b,  444,  Plate  LXXXIV) ;  but  the  relation  of  the  western  lavas 
to  the  older  rocks  of  the  eastern  range,  as  seen  from  the  Stein 
mountains  (Fig.  128)  from  Doane's  ranch  near  the  north  end  of 
the  range,  and  again  in  the  depression  between  the  ranges  back 
of  Deegan's,  seemed  to  be  best  explained  by  normal  superposi- 
tion of  the  lavas  on  the  crystallines,  followed  by  tilting  and 
erosion  without  faulting.  The  depression  between  the  front  and 
back  ranges  is  thus  to  be  interpreted  as  a  series  of  normal  sub- 
sequent valleys,  eroded  along  the  weaker  basal  members  of  the 


HighDomeofPuebloMts, 


LavaMonoclinal  Ridges 


FIG.  128.    THE  NORTH  END  OF  THE  PUEBLO  MOUNTAINS 
Looking  south  over  the  Hollis  Spur  of  the  Mid-Stein  mountains 

lava  beds  by  branches  of  streams  that  transect  the  eastern  range 
and  that  are  probably  persistent  from  an  earlier  pre-faulting 
cycle  of  erosion. 

The  eastern  base  of  the  mountains  is,  however,  unquestionably 
determined  by  a  fault  on  which  a  total  movement  of  several  thou- 
sand feet  has  probably  taken  place,  the  latest  displacements  being 
of  recent  date,  as  Russell  has  shown.  The  base-line  of  the  range 
is  of  gentle  curvature,  indifferent  to  the  structure  of  the  mass. 
An  excellent  illustration  of  this  is  seen  a  mile  or  more  south  of 
Catlow's  ranch,  where  a  boldly  outcropping  rib  of  strong  rock, 
standing  oblique  to  the  irend  of  the  range,  terminates  evenly 
with  the  adjoining  weaker  rocks  at  the  mountain  base,  and  the 
face  of  the  rib  seems  much  sheared  and  broken.  The  ravines 
and  gorges  through  which  the  range  is  drained  are  steep-walled 
and  narrow  to  their  mouths.  The  spurs  between  the  ravines  are 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        763 

abruptly  cut  off  by  the  base-line,  and  show  no  tendency  what- 
ever to  trail  forward  into  the  plain. 

Recent  faulting  along  the  mountain  base  is  shown  by  several 
topographical  features.  At  a  number  of  points  near  the  northern 
end  of  the  range,  between  Catlow's  and  Doane's,  open,  graded 
valley  floors  now  stand  a  hundred  feet  or  more  above  the  moun- 
tain base,  and  are  sharply  trenched  by  the  streams  that  formerly 
graded  them.  Uplifted  and  dissected  fragments  of  broken  fans 
are  often  seen  one  hundred  feet  or  more  above  the  mouth  of  a 
gorge,  an  excellent  example  of  this  kind  being  found  back  of 
Denio,  while  others  occur  near  Catlow's.  In  general,  the  sum- 
mits and  higher  slopes  are  of  moderate  declivity,  frequently  well 
covered  with  waste  and  exposing  few  ledges ;  while  the  walls  of 
the  cross-cut  gorges  are  steep,  with  abundant  ledges,  and  in  some 
cases  the  gorge  walls  steepen  as  they  descend  to  the  stream  line. 
The  slopes  of  the  spur  profiles  commonly  steepen  toward  the 
front  base-line  ;  their  general  descent  is  at  angles  of  from  10°  to 
25°;  but  they  often  steepen  downwards  to  30°  or  35°.  The  spur 
terminals  are,  however,  well  rounded,  and  but  faintly  recall  the 
sharp-edged  facets  of  the  Spanish  Wahsatch. 

The  southern  part  of  the  Pueblo  range  offered  the  best  illus- 
trations that  I  found  of  the  trailing  end  of  a  faulted  block,  less 
dissected  than  the  middle  part  and  therefore  probably  represent- 
ing a  sub-recent  increase  in  the  length  of  the  block  by  a  south- 
ward extension  of  its  marginal  fault.  The  front  base  of  the  range 
is  here,  as  elsewhere,  oblique  to  the  structure ;  the  crystalline 
rocks  disappear  first,  and  the  lava  monocline  continues  several 
miles  farther  south  before  dying  out.  The  frontal  escarpment 
of  the  monocline  is  very  straight  and  but  little  dissected  ;  the 
fans  at  its  base  are  low,  and  a  very  gentle  slope  of  alluvium  leads 
from  the  base-line  to  a  dead  level  playa,  half  a  mile  to  the  east. 
The  lava  monocline  is  somewhat  complicated  by  a  transverse 
fault  and  a  transverse  monoclinal  fold ;  but  the  frontal  escarp- 
ment pays  no  attention  to  these  disturbances. 

The  Stein  mountains  (Fig.  126)  continue  the  general  line  of 
the  Pueblo  mountains,  although  separated  from  them  by  the 
westward  reentrant  already  mentioned.  The  structure  of  this 
range  is,  however,  unlike  that  of  the  other  in  consisting  almost 


764  PHYSIOGRAPHIC  ESSAYS 

wholly  of  lavas  for  at  least  as  far  as  some  distance  north  of 
Andrews.  The  lavas  resemble  basalts  and  andesites,  commonly 
porphyritic.  The  range  may  be  conveniently  described  in  three 
parts.  The  southern  part  is  a  warped  monocline,  dipping  south 
and  southwest,  and  obliquely  cut  off  on  the  east  by  the  north 
and  south  mountain  base  ;  the  crest  of  this  part  of  the  range  is 
serrated.  The  middle  part  is  a  plateau-like  mass,  with  gentle 
western  dip.  The  northern  part  is  much  higher  than  the  rest ; 
it  was  generally  hidden  in  clouds  or  haze  during  my  visit,  and 
its  structure  was  not  determined. 

I  had  an  excellent  view  over  most  of  the  southern  part  of  the 
range  from  the  southeast  corner  of  the  middle  plateau  section, 
whence  a  great  extent  of  country  is  disclosed.  Alvord  valley 
has  every  appearance  of  being  a  grab  en  y  limited  by  a  fault  on  the 
east  as  well  as  the  west ;  many  low  ranges  trending  to  the  south- 
southeast  are  obliquely  cut  off  in  a  notably  even  line  along  the 
eastern  valley  margin.  To  the  northeast  an  escarpment  bordering 
the  valley  is  banked  up  with  sands  blown  from  the  extensive  playa 
of  Alvord  desert,  which  occupies  that  part  of  the  depression. 
Not  only  is  the  Alvord  depression  seemingly  a  trough,  or  graben, 
but  the  southern  and  middle  parts  of  the  Stein  mountains  are 
carved  in  what  seems  to  be  a  lifted  block,  with  a  fault  along 
the  western  as  well  as  along  the  eastern  border.  The  reason  for 
this  opinion  cannot  be  presented  as  conclusive,  for  it  is  based 
only  on  what  was  seen  from  the  point  of  view  above  named,  yet 
there  is  little  doubt  in  my  own  mind  of  its  being  correct.  The 
southern  and  middle  division  of  the  range  appeared  to  be  evenly 
cut  off  along  their  western  border,  and  this  appearance  was  espe- 
cially distinct  for  the  southern  division  where  the  western  bor- 
der trends  nearly  square  across  a  series  of  monoclinal  ridges  and 
valleys.  The  mountain  block  is  ten  or  twelve  miles  wide,  and  is 
succeeded  on  the  west  by  a  brown-gray  plain,  at  one  thousand  or 
fifteen  hundred  feet  lower  than  the  ridges,  and  two  thousand  or 
twenty-five  hundred  feet  lower  than  the  middle  plateau  division. 

The  monoclinal  structure  of  the  southern  division  has  a  strike 
in  its  western  part  to  the  west-northwest,  with  a  southerly  dip 
of  15°  or  20°.  Erosion  has  developed  a  number  of  well-defined 
ridges  and  valleys,  and  the  generally  accordant  heights  of  the 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        765 

ridges  as  they  rise  gradually  eastward  suggests  that  the  mono- 
clinal  mass  had  been  much  eroded  previous  to  the  uplift  whereby 
the  present  dissection  was  initiated.  As  the  ridges  approach 
the  crest  of  the  range,  which  lies  about  three  miles  from  its 
eastern  base,  the  strike  of  the  monocline  turns  to  the  southeast 
or  south-southeast ;  the  harder  beds  in  the  monoclinal  ridges  rise 
eastward  to  form  the  peaks,  while  the  valleys  of  the  monocline 
may  be  traced  upward  to  the  notches  in  the  serrated  mountain 
crest.  On  the  eastern  slope  the  harder  beds  form  benches  that 
descend  obliquely  southward  toward  the  eastern  mountain  base, 
where  they  are  successively  and  evenly  cut  off.  This  form  can 
be  easily  explained  as  a  block  of  a  base-leveled  monoclinal  mass, 
lifted  and  somewhat  tilted  to  the  west,  and  maturely  eroded ; 
but  I  find  it  difficult  to  explain  it  in  any  other  way.  A  sub-recent 
pause  in  the  uplift  of  the  block  is  indicated  by  the  occurrence  of 


W 


FIG.  129.    CROSS  SECTION  OF  MID-STEIN  MOUNTAINS,  LOOKING  NORTH 

well-defined  graded  basal  slopes,  independent  of  structure,  now 
raised  several  hundred  feet  above  the  Alvord  plain  and  dissected 
by  numerous  streams.  During  this  pause  the  definition  of  the 
mountain  base  would  have  been  much  less  distinct  than  it  is 
to-day ;  indeed,  ihe  base-line  would  have  been  obliterated  along 
a  considerable  fraction  of  the  mountain  front.  Renewal  of  uplift 
has  made  the  base-line  well-defined  to-day  in  the  southern  divi- 
sion of  the  range,  but  the  streams  on  the  aggraded  floor  of 
Alvord  valley  do  not  share  in  the  revival  by  which  the  same 
streams  on  the  mountain  flanks  have  trenched  the  old  graded 
slopes.  A  considerable  period  of  time  must  have  elapsed  since 
the  original  uplift  of  the  block  began,  for  the  crest  of  the  range 
is  now  worn  two  or  three  miles  back  from  the  eastern  base. 

The  middle  division  of  the  Stein  mountains  (Fig.  129)  is  a  mono- 
cline of  so  gentle  a  westward  dip  that  it  possesses  a  broadly  rolling 
upland  surface,  limited  on  the  east  by  the  strong  escarpment 
which  falls  twenty-five  hundred  or  three  thousand  feet  to  the 


;66 


PHYSIOGRAPHIC  ESSAYS 


'.  AS>  *> 

-.  '",,     •'.,  '•vtaS''-:- 

\   \    S.v          \  %«r 


?  "«'.\.V 


Alvord  trough,  by  a  lower  escarpment  which  overlooks  the  mono- 
clinal  ridges  and  valleys  on  the  south,  and  by  a  strong  escarp- 
ment again  on  the  west.  I  believe  all  these  escarpments  have 
been  worn  back  from  fault  lines,  and  there  is  some  reason  for 
thinking  that  the  fault  between  the  two  divisions  of  the  range, 
trending  west-northwest,  is  older  than  the  meridional  faults  on 
the  east  and  west ;  but  I  will  leave  the  discussion  of  this  point 

to  some  one  who  can  treat  it  in 
greater  detail.  As  in  the  south- 
ern block,  the  crest  line  of  the 
eastern  block  is  now  worn  back 
two  or  three  miles  from  base, 
indicating  a  long  period  since 
the  block  was  first  uplifted. 

The  face  of  the  eastern  es- 
carpment presents  many  graded 
slopes  between  the  ledges  of  more 
resistant  lavas.  The  spurs  be- 
tween the  obsequent  ravines  by 
which  the  escarpment  is  dis- 
sected usually  descend  with  con- 
cave slopes  toward  the  plain ; 
but  a  short  convex  profile  is 
often  seen  as  the  spur  reaches 
the  base-line.  The  lower  parts 
of  many  spurs  exhibit  well- 
defined  graded  slopes  on  the 
interstream  surfaces,  but  the 
spurs  are  now  rather  sharply 

separated  by  the  ravines,  and  thus  indicate  a  prolonged  pause 
followed  by  a  sub-recent  uplift. 

For  the  greater  part  of  the  range  front  the  fans  that  spread 
forward  from  the  ravines  are  not  faulted,  but  near  the  junction 
of  the  southern  and  middle  blocks  sub-recent  and  recent  fault- 
ing is  conspicuous.  The  most  interesting  locality  is  near  Hollis's 
ranch  (Fig.  130).  Here  several  strong  bluffs  rise  rather  boldly 
from  the  plain,  forming  terminal  escarpments  to  spurs  whose 
interstream  surface,  six  hundred  or  eight  hundred  feet  over  the 


FIG.  130.   ROUGH  MAP  AROUND 
HOLLIS'S  RANCH 

Side  of  map  is  five  or  six  miles,  north 
and  south 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        767 

mountain  base,  seems  to  have  been  well  graded  and  reduced  to 
small  relief  before  it  was  cut  by  the  streams  that  are  now  erod- 
ing sharp  ravines  in  it ;  but  the  same  streams  run  forward  on 
aggraded  gravel  fans  east  of  the  mountain  base-line.  The  bluffs 
between  the  streams  occasionally  show  outcropping  ledges,  but 
most  of  the  bluff  face  is  an  even  slope  of  slide-rock  at  an  angle 
near  35°.  Just  north  of  Hollis's  ranch  the  bluff  must  be  nearly 
one  thousand  feet  high,  but  it  rapidly  diminishes  in  strength 
north  and  south ;  and  a  mile  and  a  half  or  two  miles  from  the 
highest  part  of  the  bluff  the  mountain  base  is  of  the  usual  gentle 
expression.  The  largest  stream  that  cuts  the  bluff  has  a  sharp- 
cut  gorge  next  north  of  Hollis's  ranch,  whose  irrigated  fields  lie 
on  the  fan  that  the  stream  has  built.  Very  recent  faulting  is 
indicated  by  fragments  of  an  older  fan,  now  standing  about  one 
hundred  and  fifty  or  two  hundred  feet  above  the  present  fan  on 
either  side  of  the  canon  mouth.  Next  north  and  south  there  are 
two  "hanging  valleys,"  five  hundred  or  six  hundred  feet  over 
the  plain,  the  like  of  which  was  not  noted  elsewhere  along  the 
Stein  mountain  front. 

Some  of  these  local  features  might  be  explained,  independently 
of  faulting,  by  the  occurrence  of  a  mass  of  unusually  resistant 
rock  at  this  part  of  the  mountain  base  ;  but  in  that  case  it  might 
be  expected  that  a  greater  number  of  outcrops  would  be  seen  on 
the  bluff  faces  and  in  the  ravine  walls.  As  far  as  the  rock  was 
examined,  it  seemed  to  be  a  porphyritic  andesite,  similar  to  other 
lavas  of  the  mountain  block.  Moreover,  a  mass  of  resistant  rock 
could  hardly  be  expected  to  be  limited,  except  by  a  long  block 
fault,  so  close  to  the  line  of  the  general  mountain  front ;  and  it 
can  hardly  be  a  matter  of  chance  that  just  where  the  general 
form  of  the  mountain  base  suggests  the  most  extensive  sub- 
recent  faulting,  there  should  occur  the  strongest  recent  fault  as 
indicated  by  a  broken  gravel  fan.  Accepting  then  the  conclusion 
that  faulting  is  responsible  for  these  basal  bluffs,  it  may  be  noted 
that  they  are  roughly  in  the  stage  of  dissection  indicated  in  Fig. 
1 1 8,  except  that  all  the  edges  are  rounded  off;  but  the  initial 
upland  of  Fig.  1 18  is  here  represented  by  the  graded  interstream 
surfaces  that  had  been  worn  down  to  gentle  slopes  before  the 
sub-recent  faulting  began.  There  is  some  reason  for  associating 


768  PHYSIOGRAPHIC  ESSAYS 

this  renewed  uplift  with  the  fault  that  has  been  above  suggested 
to  separate  the  southern  and  middle  division  of  the  range  ;  but 
more  detailed  field  work  is  necessary  on  this  point. 

The  northern  part  of  the  middle  Stein  escarpment  is  breached 
by  a  large  valley  that  comes  southeast  from  the  high  Steins,  and 
a  small  plateau-like  block  is  thus  cut  off  from  the  main  mass  as 
shown  in  Fig.  126.  Several  low  lava-bed  monoclines,  of  gentle 
dip  to  the  southwest,  extend  southeast  from  the  detached  block  ; 
they  gradually  dip  underground  near  the  southern  end  of  the 
Alvord  desert  (playa)  and  their  trend  very  strongly  suggests  a 
connection  with  the  monoclinal  ridges  of  similar  strike  on  the 
eastern  side  of  the  Alvord  trough.  It  is  certainly  reasonable  to 
infer  a  fault  with  downthrow  on  the  southeast  between  these 
low  lava  monoclines  and  the  high  detached  block  that  over- 
looks them. 

The  Quaternary  lake  that  Russell  has  described  as  occupying 
the  Alvord  trough  left  shore-lines  of  moderate  strength  at  vari- 
ous levels  up  to  a  few  hundred  feet  over  the  present  lake  bed 
plain.  The  best  examples  noted  are  seen  on  the  low  lava  mono- 
clines, just  mentioned,  where  faint  benches  are  developed  ;  in 
the  embayment  of  the  main  depression  that  heads  between  the 
low  monoclines  and  the  main  escarpment  of  the  middle  Stein 
plateau,  where  two  cross-bay  bars  were  built  to  a  height  of  ten 
or  twenty  feet,  about  a  mile  north  of  Andrews  ;  beneath  the 
strong  bluffs  just  north  of  Hollis's  ranch,  where  shore-lines  are 
associated  with  the  chief  fan  delta  of  that  district ;  and  near  the 
north  end  of  the  Pueblo  range,  between  Doane's  and  Catlow's, 
where  what  seems  to  be  a  long  spit  was  built  out  into  the  lake 
from  the  bend  in  the  mountain  front  near  the  beginning  of  the 
reentrant  between  the  Pueblo  and  the  Stein  ranges. 

To  any  one  who  wishes  to  give  a  month  to  the  study  of  a 
well-defined  graben,  bordered  east  and  west  by  uplifted  and 
well-dissected  mountain  blocks,  Alvord  valley  may  be  highly 
commended. 

The  Shoshone  Range.  On  returning  from  Oregon  I  passed  by 
the  northern  end  of  the  Shoshone  range  in  north  central  Nevada 
in  an  eastbound  afternoon  express  train  on  the  Central  Pacific 
Railroad  between  Argenta  and  Shoshone.  My  notes,  rather 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        769 

hurriedly  written  at  the  time,  are  as  follows  :  "  A  very  fine  fault 
block,  with  manifest  recent  and  sub-recent  faulting.  Broken 
fans  ;  light-colored  basal  slopes,  ripped  with  gullies ;  uplifted 
grades,  truncated  spurs,  revived  streams  in  full-bodied  spurs ; 
spur  tops  dark  gray,  sides  lighter ;  tops  graded,  sides  ripped. 
Even  fronted  base,  facing  west  and  north ;  all  excellent  exam- 
ples for  study.  At  some  points  on  west  base,  very  short  fans, 
as  if  plain  had  been  depressed." 

This  specimen  of  a  block  mountain  interested  -me  greatly.  It 
served  as  an  example  for  rapid  review  of  many  features  that  I 
had  studied  at  more  leisure  in  other  ranges.  It  sufficed  to  show 
that  physiographic,  evidence  of  block  faulting  may  be  easily  and 
quickly  recognized  when  it  is  looked  for.  It  confirmed  my  opin- 
ion that  such  evidence  compares  well  in  logical  and  compulsory 
value  with  the  stratigraphic  evidence  on  which  the  demonstration 
of  faulting  is  usually  dependent.  It  strengthened  my  belief  in 
the  importance  and  the  possibility  of  describing  all  land  forms 
rationally  and  systematically  in  view  of  their  evolution. 

The  description  of  the  Shoshone  range  in  the  reports  of  the 
4<Dth  Parallel  Survey  is  so  closely  limited  to  matters  of  geolog- 
ical structure  —  as  was  natural  enough  at  the  time  the  survey 
was  made,  and  the  reports  were  written  —  that  no  consideration 
is  given  to  the  physiographic  features  here  discussed.  The  range 
is  not  mentioned  in  Gilbert's  or  Russell's  reports,  or  in  Spurr's 
essay.  The  fuller  meaning  of  my  notes,  supplemented  by  the 
maps  and  reports  of  the  4Oth  Parallel  Survey,  and  by  the  thoughts 
that  accompanied  the  observations,  is  as  follows  : 

The  northern  ten  miles  of  the  Shoshone  range  in  north  cen- 
tral Nevada  is  an  east-dipping  monocline  of  Weber  quartzite 
overlaid  by  basalt  (4Oth  Par.  Surv.,  Map  4,  west  half).  It  is  bor- 
dered on  the  north  and  west  by  the  open  alluvial  plain  through 
which  Humboldt  river  wanders.  From  five  to  ten  miles  north  of 
the  range  lies  Shoshone  mesa,  composed  of  rhyolite  covered  by 
basalt,  fronting  southward  in  a  strong  escarpment,  and  dipping 
gently  northward.  The  Central  Pacific  Railroad  skirts  the  base 
of  the  range  for  twelve  miles  along  its  northern  end,  giving  a 
good  view  of  part  of  its  western  outcropping  face  and  its  north- 
ern cross  section.  The  range  has  every  appearance  of  being  a 


770  PHYSIOGRAPHIC   ESSAYS 

dissected  monoclinal  fault  block,  owing  its  relief  to  gradual  and 
long-continued  displacement,  whose  later  movements  are  clearly 
recorded  in  the  form  of  its  base.  Although  the  observations  on 
which  this  statement  is  made  were  made  only  from  a  passing 
train,  they  are  believed  to  be  fully  deserving  of  credit.  It  should 
be  understood,  however,  that  they  apply  only  to  the  northern 
part  of  the  range.  The  passage  from  observation  to  explanation 
may  be  stated  as  follows  : 

The  first  feature  to  be  noted  is  the  block-like  appearance  of 
the  mass,  especially  as  indicated  by  its  basal  outline.  The  base- 
line is  relatively  well  defined,  of  very  small  irregularity  and  of 
moderate  curvature  ;  the  basal  mass  is  continuous  but  for  the 
narrow  ravines  that  divide  it  into  full-bodied  spurs. 

In  the  second  place,  attention  should  be  given  to  the  contrast 
of  the  heavy  mountain  mass  and  the  broad  piedmont  plain.  The 
lower  slopes  of  the  mountain  are  strong ;  they  change  rather 
abruptly  into  the  broad  alluvial  plain  that  stretches  away  un- 
broken for  several  miles.  The  depression,  floored  by  the  pied- 
mont plain  and  drained  by  Humboldt  river,  is  five  or  ten  miles 
wide  between  Shoshone  range  on  the  south  and  Shoshone  mesa 
on  the  north,  and  does  not  give  the  impression  of  being  a  normal 
trunk  valley,  eroded  in  a  once  continuous  rock  mass ;  for  if  it 
were  of  such  origin,  the  branch  valleys  by  which  the  mountain  is 
drained  ought  to  be  of  correspondingly  advanced  development 
with  broad-open  floors  ;  while  as  a  matter  of  fact  the  branch 
valleys  are  narrow  to  their  mouths  at  the  mountain  base.  More- 
over, in  the  neighborhood  of  Palisade,  twenty-five  or  thirty  miles 
farther  east,  the  Humboldt  river  has  what  appears  to  be  a  per- 
fectly normal  valley,  a  narrow  canon  cut  in  lavas.  The  broad 
plain  and  the  narrow  canon  cannot  both  be  parts  of  an  undis- 
turbed, normally  eroded  valley ;  and  as  the  narrow  canon  is 
manifestly  of  river  origin,  the  broad  depression  must  be  other- 
wise explained. 

The  depression  might  at  first  sight  be  regarded  as  a  down- 
warped  part  of  a  normal  valley,  heavily  aggraded  with  alluvium ; 
but  this  supposition  is  untenable  because  the  alluvium  does  not 
invade  the  ravines  on  the  mountain  flank  as  it  certainly  should  if 
the  ravines  had  been  carved  with  respect  to  a  now-buried  trunk 


MOUNTAIN  RANGES  OF  THE  GREAT  BASIN        771 

valley.  Some  other  origin  than  erosion  must  therefore  be  dis- 
covered for  the  depression  alongside  of  the  mountain. 

Differential  movement  or  faulting,  the  only  other  conceivable 
origin  of  the  depression,  —  the  supposition  that  the  mountain 
rocks  were  originally  deposited  only  on  their  present  limited  area 
need  not  be  considered,  —  is  not  only  permissible  by  its  appro- 
priateness to  the  outline  of  the  mountain  base,  but  it  receives 
strong  support  from  the  abundant  evidence  of  the  recently  con- 
tinued movement  on  the  fracture  by  which  the  depression  and 
the  mountain  block  were  originally  outlined.  The  evidence  to 
this  end  is  interesting  from  its  variety  and  its  accordance. 

Graded  valley  floors  of  moderate  width  dissect  the  mountain 
side,  but  their  floors  lie  one  hundred  or  two  hundred  feet  above 
the  plain ;  the  valley  streams  have  now  entrenched  narrow  ravines 
in  the  valley  floors,  and  thus  flow  out  upon  alluvial  fans  at  the 
mountain  base.  The  spurs  between  the  ravines  are  of  rounded, 
full-bodied  form ;  they  do  not  taper  away  on  the  plain,  but  are 
rather  sharply  cut  off  by  the  basal  slope  of  the  mountain.  The 
upper  surface  of  the  spurs  is  maturely  graded,  but  their  lower 
slopes  are  often  gashed  or  "  ripped  "  by  little  gullies,  suggestive 
of  active  erosion ;  the  color  of  the  spur  slopes  is  therefore  pre- 
vailingly lighter  than  that  of  the  spur  tops.  Many  of  the  fans 
are  broken  by  low  scarps  closely  in  line  with  the  mountain  base  ; 
this  indicates  a  continuation  of  faulting  into  a  very  recent  period. 
Some  of  the  fans  at  the  northern  end  of  the  western  base  of  the 
range  seem  unusually  low,  as  if  the  plain  there  had  been  de- 
pressed while  the  mountain  was  rising.  Taken  all  together,  one 
can  hardly  imagine  more  satisfactory  evidence  of  block  faulting. 

It  should  be  noted,  however,  that  the  higher  parts  of  the 
mountain  seem  to  have  been  abundantly  dissected  since  the 
faulting  began.  The  west-facing  scarp  of  the  basalt  sheet  is 
now  a  mile  or  more  back  from  the  west-facing  scarp  of  the 
underlying  strata,  but  the  accordant  outlines  of  the  two  scarps 
strongly  suggest  the  original  definition  of  both  by  the  same 
surface  of  fracture.  Deliberate  and  detailed  study  of  this 
range  would  well  repay  the  observer  who  could  undertake  it. 


772  PHYSIOGRAPHIC  ESSAYS 

REFERENCES 

Davis,  W.  M.  (a)  "The  Ranges  of  the  Great  Basin:  Physiographic  Evi- 
dence of  Faulting."  Science,  XIV  (1901),  457-459. 

(£)  "  The  Stream  Contest  along  the  Blue  Ridge."    Bull.  Geog.  Soc.  Phila- 
delphia (1903). 

Diller,  J.  S.  "  Notes  on  the  Geology  of  Northern  California."  U.  S.  Geol. 
Surv.,  Bull.  No.  33  (1886). 

Emmons,  S.  F.  Report  of  the  Geological  Survey  of  the  Fortieth  Parallel. 
Vol.  II,  Descriptive  Geology.  Washington,  1877. 

Gilbert,  G.  K.  Geographical  and  Geological  Explorations  and  Surveys  West 
of  the  One  Hundredth  Meridian,  (a)  Progress  Report,  48-52,  Wash- 
ington, 1874;  (£)  Vol.  Ill,  Geology,  17-187,  Washington,  1875. 

Johnson,  D.  W.  "  Block  Mountains  in  New  Mexico."  Am.  Geol.  XXXI, 
(1903),  135-139. 

King,  C.  Report  of  the  Geological  Survey  of  the  Fortieth  Parallel,  (a)  Vol. 
Ill,  Mining  Industry,  Washington,  1870;  (£)  Vol.  I,  Systematic  Geol- 
ogy, Washington,  1878. 

Russell,  I.  C.  (a)  "Geological  History  of  Lake  Lahontan,  a  Quaternary 
Lake  of  Northwestern  Nevada."  U.  S.  Geol.  Surv.,  Mon.  XI  (Wash- 
ington, 1885). 

(t>)  "  Geological  Reconnaissance  in  Southern  Oregon."    U.  S.  Geol.  Surv. 
IV Ann.  Rep.  (Washington,  1884),  431-464. 

Spurr,  J.  E.  "  Origin  and  Structure  of  the  Basin  Ranges."  Bull.  Geol.  Soc. 
Am.,  XII  (1901),  217-270. 


INDEX 


Accidents  in  the  cycle,  180,  274;  cli- 
matic, 1 80,  289;  volcanic,  180,  290 

Activities  of  the  lands,  139 

Adjustment,  stream,  262,  343,  434,  488 ; 
examples  of,  439 ;  process  of,  435 ; 
terminology,  438 ;  Tertiary,  of  the 
Juniata,  476;  with  revival,  442 

Adolescence  of  cycle,  176,  430 

Aggraded  streams,  259,  392 

Aire  river,  609 

Alaska,  hanging  valleys  of,  652,  686 

Alaskan  boundary,  25 

Almanac,  Nautical,  232 

Alpine  valleys,  80,  640,  651,  686 

Alvord  valley,  764 

American    school    of    physiographers, 

144,  339 

Anaclinal  streams,  510 
Angle  of  repose,  267 
Animals  and  plants  in  geography,  134, 

144 
Antecedent  stream,  81,  274,  444,  447, 

486 

Anthracite  basins,  drainage  of,  465 
Appalachian  drainage,  studies  of,  417 
Ardennes,  615 

Argentine-Chilian  boundary,  25 
Arid  climate,  geographical  cycle  in,  296 
Aristotle,  219 

Astronomical  geography,  100,  219 
Atmosphere,  49,  136,  213,  228 
Austria,  topographical  maps  of,  191 
Autumn  field  studies,  240 
Axis  of  the  earth,  221  ;  relation  to  orbit, 

232 

Bar  river,  609 

Bars,  off-shore,  707 

Base-level,  84,  in,  171,  175,  275,381, 

390,  397  ;  kinds  of,  400 ;  local,  244 
Base-leveling,  leveling  without,  306 
Basin  range  province,  298,  725 
Beheaded  streams,  438,  500,  600,  605, 

609 

Betrunked  streams,  181 
Blanford,  W.  T.,  686 
Block  mountains,  725 
Blue  Ridge,  737 
Bohemia,  373 


Boundaries,  political,  25,  39,  59 
Branch  valleys,  development   of,  260; 
relation  to  trunk,  645 

Campbell,  M.  R.,  82 

Cantal,  639 

Capture,  river,  82,  438,  461,  477,  480, 

500,  587,  737  ;  elbowr  of,  602 
Cartographer,  156 
Cataclinal  streams,  510 
Catastrophism,  71,  72 
Cayuga  lake,  682 
Chamberlin,  T.  C.,  694 
Channels  of  rivers  and  glaciers,  657 
Charts,  188 
Chelan,  lake,  685 
Classification,  of  land  forms,  77,   107, 

249,  252  ;  of  geography,  212 
Climate,  normal,  296 
Climatic  changes,  289 ;  control,  134, 143 
Coast  Survey  charts,  188,  228 
Coastal  plain,  198 
Cod,  Cape,  690 

Colleges,  geography  in,  28,  146,  165 
Colorado  canon,  80,  91,  202 
Colorado  plateaus,  203,  30*4 
Como,  lake,  667 
Complexity  of  geography,  5,  37 
Composite  topography,  181,  273 
Connecticut  river,  89,  113,  529,  578 
Consequent  streams,  81,  172,  174,  256, 

447 

Continental  shelf,  133 

Control,  climatic,  134,  143 

Corrie  basins,  671 

Cut-offs,  536;  of  the  Cpnnecticut,  581  ; 
of  the  Meuse,  592 ;  of  the  Missis- 
sippi, 582 

Cycle,  170,  249,  408;  agencies  of,  288; 
complications  of,  279;  deductive 
nature  of,  281  ;  in  an  arid  climate, 
296;  ideal,  254,  279;  of  glacial  ero- 
sion, 288,  658  ;  interruptions  of,  180, 
203,  272,  285,  315;  stages  in,  176;  of 
the  shore-line,  290 

Davis,  C.  H.,  692 

Deductive  method,  58,   165,    170,  179, 


773 


774 


INDEX 


Degradation,  408,  559 

Denudation,  79,  in,  323,  343,  344,  408, 

421,  425 

Desert  drainage,  diversion  of,  317 
Desert  leveling,  310 
Deserts,  kinds  of,  311 
Disciplinary  value  of  geography,  63 
Distributaries,  glacial,  666 
Distribution,  geography   as  the    study 

of,  8 
Divides,   174,  261 ;   migration  of,   434, 

442,  477,  488,  500,  596,  737 
Drowned  valleys,  274,  441,  697 
Dryer,  C.  R.,  406 
Dutton,  C.  E.,  81,  332,  369 

Earth,  as  a  globe,  100,  213,  218;  axis 
of,  221,  233 ;  orbit  of,  233,  234 ;  revo- 
lution of,  229;  rotation  of,  104,  220; 
shape  of,  219;  size  of,  224 

Earthquakes,  141 

Elementary  schools,  geography  in,  105 

Engineering  schools,  geography  in, 

154 

English  school  of  physiographers,  339 

Entrenched  or  incised  meanders,  588, 
590,  594,  636 

Episode,  181 

Equator,  222 

Equinox,  232,  234 

Equipment,  geographical,  216 

Eratosthanes,  224 

Eudoxus,  219,  222 

Europe,  geography  in,  72,  134 

Evans,  Lewis,  414 

Evolution,  geographical,  131  ;  inor- 
ganic, 86 

Exercises,  laboratory,  62,  210 

Experimental  geography,  211 

Explorers,  157 

Extended  streams,  181 

Faceted  spurs,  746 

Fault-block  mountains,  725 

Features  of  the  lands,  140 

Field  work,  236 

Fiords,  653,  669,  682,  683 

Flood  plain,  95,  259,  261,  264,  433 

Forbes,  J.  D.,  677 

Forms  assumed  by  land  waste,  276 

France,  Army  Staff  map,  190 

France,  central  plateau  of,  371 ;  glacial 

erosion  in,  636 ;  rivers  of,  587 
Freeman,  F.,  692 

Gannett,  H.,  685 
Geikie,  A.,  80,  325 
Geikie,  J.,  670,  677,  683 


Genetic  classification  of  land  forms, 
107,  249,  252 

Geographical  equipment,  152,  188,  216 

Geographical  errors,  102 

Geographical  evolution,  131 

Geographical  excursions,  116,  236 

Geographical  journals,  154 

Geographical  laboratory,  57,  216 

Geographical  observations,  215 

Geographical  studies,  sequence  of,  151 

Geographical  teaching,  193 

Geographical  terminology,  26 

Geography,  astronomical,  100,  218; 
classification  of,  18,  212;  in  the  col- 
leges, 28,  146,  165;  commercial,  18, 
67  ;  complexity  of,  5,  37,  38  ;  content 
of,  3;  descriptive,  66,  87,  105;  dis- 
tribution of  the  divisions  of,  66 ; 
educational  value  of,  68 ;  exercises 
in,  210;  expansion  of,  16;  field  work 
in,  236;  in  the  elementary  schools, 
105  ;  in  the  engineering  schools,  154 ; 
in  the  grammar  schools,  115,  151  ;  in 
the  high  school,  67, 1 29, 152,21 5,  237 ; 
in  scientific  schools,  149;  in  the  uni- 
versity, 28,  146,  165;  mathematical, 
100,  218;  modern  33,  279;  political, 
14;  practical  side  of,  68;  progress 
of,  23  ;  rational  element,  63  ;  regional, 
10,  41,  55,  144;  relation  to  geology, 
196,  214,  293;  sequence  of  parts  of, 
64;  subdivisions  of,  18,  66,  212;  sys- 
tematic, 10,  41,  43,55;  teaching  of, 
87;  theoretical,  251;  time  needed 
for  a  course  in,  99 ;  unity  of,  36 

Geological  structure  as  a  basis  of  classi- 
fication, 107 

Geological  Survey  of  the  United  States, 
1 88 

Geologist,  39,  77 

Geology,  18,  71,  73,  147,  196,  214,  293 

Geometry,  213 

Geomorphogeny,  254 

Geomorphology,  83 

German  Empire,  map,  191 

Germany,  geography  in,  72,  587 

Gilbert,  G.  K.,  351,  686,  726 

Glacial  canons,  635,  678,  68 1 

Glacial  distributaries,  666 

Glacial  erosion,  617,  635;  argument 
against,  627  ;  cycle  of,  288,  658,  673 ; 
measure  of,  653 

Glacial  sculpture,  617 

Glaciers,  channels  of,  657,  668  ;  load  of, 
664 

Globe,  earth  as  a,  100,  213,  218 

Gobi,  desert  of,  318 

Grade,  381,  390,  393,  397,  400 


INDEX 


775 


Graded  shore-line,  702 

Graded  slope,  175 

Graded  stream,  175,  243,  258,  260,  389, 

39°,  533 

Graded  valley  floors,  257 
Graded  valley  sides,  266 
Grammar  schools,  geography  in,  115, 

ISl 
Great  Britain,  Ordnance  Survey  map, 

190 

Green  river,  444,  504 
Greenwood,  G.,  78 
Gulliver,  F.  P.,  79 
Guyot,  A.,  70,  76,  133 

Hanging  valleys,  563,  645,  677 

Harker,  A.,  686 

Hayes,  C.  W.,  82,  406 

Heim,  A.,  80 

Hershey,  O.  H.,  687 

High  school,  geography  in,  67,  129,  152, 

215.  237 

History  of  a  river,  430 
History,  teaching  of,  39,  159 
Hitchcock,  E.,  691 
Humboldt,  F.  H.  A.  von,  73 
Huxley,  T.  H.,  75,  134 

Incised  meanders,  588,  590,  594 

Inductive  study,  169 

Infancy  of  cycle,  176 

Ingressin  river,  607 

Initial  drainage,  172 

Inorganic  evolution,  86 

Insequent  stream,  174 

Interruptions  of  the  cycle,  180,  203, 
272;  in  an  arid  climate,  315;  of  the 
shore-line,  290;  due  to  tilting,  285 

Italy,  geography  in,  72 

Johnson,  W.  D.,  399 
Journals,  geographical,  154 
Juniata  river,  454,  467,  476 
Jura  mountains,  453 

Kentucky,  200 

Kittatinny  mountain  and  valley,  489 

Knobs  in  glaciated  areas,  638 

Laboratory  exercises,  62,  186 

Laboratory,  geographical,  57,  168,  216 

Lands,  physical  geography  of,  70  ;  activ- 
ities of,  139;  features  of,  140;  waste 
of,  142 

Language,  geographical  elements  in,  20, 

54 

Lapparent,  A.  de,  682 
Lateral  cutting  of  rivers,  533 


Latitude,  132,  222 

Lauterbrunnen  valley,  650 

Lava  caps,  201 

Lesley,  J.  P.,  78 

Leveling  without  base-leveling,  306 

Load,  relation  to  river  ability,  260 ;  of 

glaciers,  664 

Location,  geography  as  the  study  of,  8 
Longitude,  132,  226 
Lubbock,  J.,  678 
Lugano,  lake,  647 

McGee,  W.  J.,  77,  333,  396,  487,  678, 
68 1 

Maggiore,  lake,  648 

Magnetism,  terrestrial,  228 

Man  in  geography,  35,  133,  144 

Map  projection,  227 

Map  scales,  122 

Maps,  193,  214;  drawing  of,  122;  foreign, 
189;  making  of,  122  ;  topographical, 
166,188;.  United  States  government, 
188  ;  weather,  63,  229 

Marindin,  H.  L.,  694 

Marine  erosion,  79,  323,  700,  703 

Marne  river,  599 

Mathematical  geography,  100,  218 

Maturity,  stage  of  the  cycle,  177,  200 

Meanders,  compressed,  550 ;  develop- 
ment of,  264,  532 ;  incised,  588,  590, 
594,  636 ;  slipping  of,  549 ;  sweeping 
and  swinging,  559 

Meridians,  221 

Merrimac  river,  89,  585 

Mesas,  201 

Methods  and  models,  193 

Meuse  river,  587 

Migration  of  divides,  434,  442,  477,  488, 
500,  596,  737 

Mississippi  River  Commission,  maps, 
1 88,  535 

Mitchell,  H.,  693 

Models,  193,  214 

Monadnock,  362,  591 

Moselle  river,  587 

Mountains,  77,80,  109,617,  725;  fault- 
block,  725  ;  glacial  sculpture  of,  617  ; 
of  the  Great  Basin,  725 

National  Education  Association,  25,  57, 
64,  76,  129,  136,  144,  237 

Nautical  Almanac,  232 

New  England,  uplands  of,  91,  in  ;  ter- 
races of,  514 

New  Jersey,  coast  of,  712;  rivers  of, 
485  ;  topography  of  northern,  489 

Newberry,  J.  S.,  80 

Niagara  falls,  88 


776 


INDEX 


Nile  cataract,  88 

Norway,  glacial  erosion  in,  635  ;  maps 
of,  191 

Obsequent  streams,  264 
Ocean,  treatment  of  the,  138 
Off-shore  bars,  707 
Old  age,  stage  of  cycle,  177 
Old  plain,  example  of,  201 
Ontography,  10,  n,  14,  17,  34,  51  ;  re- 
gional, 55;  systematic,  50,  55 
Orbit  of  the  earth,  233 
Outdoor  observations,  61 
Over-deepened  valleys,  646,  673 

Pagny  river,  607 
Pedagogical  principles,  119 
Penck,  A.,  271,  338,  373,  686 
Peneplain*  1 1 2,  323,  350,  352,  381,  405 
Pennsylvania,  in,  413;  events  of  the 
Quaternary  cycle  in,  480 ;  events  of 
the  Tertiary  cycle  in,  473 ;  geological 
history  of,  418;  migration  of  the  At- 
lantic-Ohio divide,  477  ;  Permian  to- 
pography   and    drainage    of,    451  ; 
reversal  of  rivers  in,  459 ;  rivers  and 
valleys  of,  413 ;  topography  of,  427 

Percival,  J.  G.,  353 

Philology,  20,  54 

Physical  geography,  1 5,  34,  70 ;  abroad, 
134;  denned,  105,  129;  exercises  in, 
210;  field  work  in,  236;  in  the  gram- 
mar schools,  115,  151;  in  the  high 
school,  129,  215,  236;  in  the  uni- 
versity, 165;  treatises  on,  74.  See 
also  Geography 

Physiographic  controls,  17,  76,  144 

Physiography,  10,  15,  34,  51,  and  Part 
Two ;  regional,  47,  48,  67  ;  subdivi- 
sions of,  44 ;  systematic,  43,  48,  67. 
See  also  Physical  geography  and 
Geography 

Plains,  examples  of,  197  et  seq.  ;  of 
marine  denudation,  323 ;  and  pene- 
plains, 405 

Plants  and  animals  in  geography,  134, 
144 

Playfair,  J.,  72,  80,  563,  618 

Polar  flattening,  227 

Poles,  222 

Political  geography,  14,  87 

Powell,  J.  W.,  81,  84,  331,  350,  381,  404, 
405,  486,  504 

Preparation  of  teachers,  56 

Prestwich,  J.,  80 

Primary  schools,  geography  in,  115' 

Profile  of  equilibrium,  175  ;  stream,  174 

Progress  of  geography,  23 


Provincetown  harbor,  720 
Pueblo  mountains,  760 

Race  Point,  Mass.,  717 

Rainfall,  explanation  of,  103 

Ramsay,  A.  C.,  79,  323 

Rational  treatment  of  geography,  63, 
65,  72,  131 

Ratzel,  F.,  13,  1 8,  51 

Red  River  of  the  North,  197 

Regional  geography,  10,  41,  55,  144 

Regional  ontography,  55 

Regional  physiography,  47 

Relation,  of  river  ability  to  load,  260; 
of  trunk  and  branch  valleys,  645 

Residual  mountains,  736;  of  the  Great 
Basin,  738 

Reversal  of  rivers,  459,  510 

Revived  streams,  181,  441,  442,  494 

Rhue  river,  636,  673 

Richter,  E.,  682 

Richthofen,  F.  von,  79 

Ritter,  K.,  33,  34,  71,  72,  129 

Rivers,  adjusted,  262,  343,  434,  439, 
476,488;  anaclinal,  510;  antecedent, 
81,  274,  444,  447,  486;  behavior  of  a 
wandering,  532  ;  branches,  260,  645  ; 
capture,  82,  596 ;  characteristics  of, 
242 ;  complete  cycle  of,  430 ;  com- 
plex, 446 ;  composite,  446,  502  ;  com- 
pound, 446,  502 ;  consequent,  81, 
447;  graded,  175,  243,  258,  260,  389, 
390,  533 ;  history  of,  430 ;  inverted, 
603 ;  lateral  cutting  of,  533 ;  mean- 
dering, 264,  532,  549,  559 ;  profile  of, 
174;  reversed,  459,  510;  revived, 
494 ;  simple,  446 ;  subsequent,  82, 
172,  177,  487;  superimposed,  444, 
469,  487,  494;  and  valleys,  141 

River  terraces,  514;  theory  of,  531 

Rotation  of  the  earth,  220 ;  influence 
of,  104 

Russell,  I.  C.,  78,  658,  677,  679,  728 

Russia,  maps,  191 

Ste.  Austreberte  river,  588 

Schooley  peneplain,  489 

Schools,  progress  of  geography  in,  23. 

See    High,    Grammar,   and   Primary 

schools 
Scientific  schools,  physical  geography 

in,  149 

Scotland,  glacial  valleys  in,  686 
Scrope,  G.  P.,  78 
Sculpture  of  mountains,  617,  625 
Seasons,  229 
Seine  river,  588 
Sequence  of  the  parts  of  geography,  64 


INDEX 


777 


Sequential  drainage,  257 

Shape  of  the  earth,  219 

Shore-lines,  143,  178,  690  ;  cycle  of,  290  ; 

graded,  702  ;  topography  of,  79 
Shore  profiles,  700 
Shoshone  falls,  88 
Shoshone  range,  768 
Size  of  the  earth,  224 
Slope,  graded,  175 
Sonoran  district,  Mexico,  318 
Spits,  710 
Spurr,  J.  E.,  725 

Spurs  of  the  Wahsatch  range,  747 
Spurs,  wave-cut,  751 
Stein  mountains,  760 
Streams.    See  Rivers 
Subsequent  streams,  82,  172,  177,  262, 

487>_  497 

Superimposed  rivers,  444,  469,  487,  494 
Superimposition  of  the   Susquehanna, 

469 

Susquehanna  river,  461,  466,  467,  469 
Sutlej  river,  508 

Systematic  geography,  10,  41,  43,  55 
Systematic  ontography,  50,  55 
Systematic  physiography,  43,  48,  67 

Tarr,  R.  S.,  350,  682 

Teachers'  meetings,  118,  217 

Teachers,  preparation  of,  56,  158 

Teaching  of  geography,  87  ;  what  to 
avoid  in,  95 

Teleology,  72,  131 

Terminology,  of  the  cycle,  292 ;  geo- 
graphical, 26,  271  ;  of  rivers  changed 
by  adjustment,  438  ;  time  element  in, 
251 ;  of  wandering  rivers,  537 

Terrace  patterns,  558. 

Terraces,  514;  defended,  547;  effect  of 
rock  barriers  on,  556;  ideal,  538; 
kinds  of,  516;  theory  of,  531 

Terrestrial  magnetism,  228 

Text-books,  geographical,  117,  159 

Theoretical  geography,  251 

Thoreau,  H.  D.,  692 

Tibet,  318 

Ticino  valley,  640,  674 

Tilting,  effect  on  streams,  82  ;  as  an  in- 
terruption of  the  cycle,  285 

Time  element  in  geographical  termi- 
nology, 251 


Time  needed  for  a  geographical  course, 

99 

Topographer,  150 
Topographical  maps,  166,  188 
Topography,  composite,  181,  273 
Trunk  valleys,  645 

Uniformitarianism,  71,  78 

United  States  Coast  Survey,  maps,  188, 

228 
United  States  Geological  Survey,  maps, 

1 88 
United    States    government    bureaus, 

maps,  1 88 

Unity  of  geography,  36 
Upham,  W.,  693 
Utah,  202,  725 

Valley  floors,  graded,  257 

Valley  sides,  graded,  266 

Valley  walls,  over-steepened,  673 

Valleys,  77,  80,  141 ;  antecedent,  81, 
274,  444,  447,  486 ;  broken-bedded, 
661 ;  consequent,  81,  172,  174,  256, 
447  ;  hanging,  645,  653,  677  ;  over- 
deepened,  646,  673  ;  relation  of  trunk 
to  branch,  645 

Van  Hise,  C.  R.,  362 

Varigradation,  396 

Volcanic  accidents,  180,  290 

Wahsatch  mountains,  734,  742,  747 

Wallace,  A.  R.,  680 

Waste,  forms  assumed  by,  276 

Water  gaps,  454 

Water  partings,  261 

Waterfalls,  88,  677 

Wave  action,  323,  700,  701,  703 

Wave-cut  spurs,  751 

Weather,  212 

Weather  maps,  63,  229 

Weathering,  214;  field  lesson  on,  240 

West  Virginia,  199 

Weule,  K.,  694 

Whiting,  H.  L.,  693 

Winds,  103  ;  erosion  by,  299 

Year,  determination  of  length  of,  232 
Yosemite  falls,  88 
Young  plain,  examples  of,  197 
Youth,  stage  of  the  cycle,  176 


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